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Journal of engineering for gas turbines and power: Transactions of the ASME |
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Ajouter le résultat dans votre panierEffects of target size on foreign object damage in gas-turbine grade silicon nitrides by steel ball projectiles / Sung R. Choi in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 134 N° 5 (Mai 2012)
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 08 p.
Titre : Effects of target size on foreign object damage in gas-turbine grade silicon nitrides by steel ball projectiles Type de document : texte imprimé Auteurs : Sung R. Choi, Auteur ; Zsolt Rácz, Auteur Année de publication : 2012 Article en page(s) : 08 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Ceramics Cracks Fracture Gas turbines Silicon compounds Steel Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Foreign object damage (FOD) phenomena of two gas-turbine grade silicon nitrides (AS800 and SN282) were assessed at ambient temperature applying impact velocities from 20 to 300 m/s using 1.59-mm diameter hardened steel ball projectiles. Targets in a flexural configuration with two different sizes (thicknesses) of 1 and 2 mm were ballistic-impacted under a fully supported condition. The severity of impact damage, as well as the degree of post-impact strength degradation, increased with increasing impact velocity, increased with decreasing target size, and was greater in SN282 than in AS800 silicon nitride. The critical impact velocity where targets fractured catastrophically decreased with decreasing target size and was lower in SN282 than in AS800. Overall, FOD by steel projectiles was significantly less than that by silicon-nitride ceramic counterparts, due to much decreased Hertzian contact stresses. A correlation of backside cracking velocity versus target size was made based on a simplified elastic foundation analysis. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...] [article] Effects of target size on foreign object damage in gas-turbine grade silicon nitrides by steel ball projectiles [texte imprimé] / Sung R. Choi, Auteur ; Zsolt Rácz, Auteur . - 2012 . - 08 p.
Génie mécanique
Langues : Anglais (eng)
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 08 p.
Mots-clés : Ceramics Cracks Fracture Gas turbines Silicon compounds Steel Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Foreign object damage (FOD) phenomena of two gas-turbine grade silicon nitrides (AS800 and SN282) were assessed at ambient temperature applying impact velocities from 20 to 300 m/s using 1.59-mm diameter hardened steel ball projectiles. Targets in a flexural configuration with two different sizes (thicknesses) of 1 and 2 mm were ballistic-impacted under a fully supported condition. The severity of impact damage, as well as the degree of post-impact strength degradation, increased with increasing impact velocity, increased with decreasing target size, and was greater in SN282 than in AS800 silicon nitride. The critical impact velocity where targets fractured catastrophically decreased with decreasing target size and was lower in SN282 than in AS800. Overall, FOD by steel projectiles was significantly less than that by silicon-nitride ceramic counterparts, due to much decreased Hertzian contact stresses. A correlation of backside cracking velocity versus target size was made based on a simplified elastic foundation analysis. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...]
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 07 p.
Titre : Assessment of current chemiluminescence kinetics models at engine conditions Type de document : texte imprimé Auteurs : Eric Petersen, Auteur ; Madeleine Kopp, Auteur ; Nicole Donato, Auteur ; Felix Güthe, Auteur Année de publication : 2012 Article en page(s) : 07 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Chemiluminescence Engines Gas turbines Reaction kinetics Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Chemiluminescence continues to be of interest as a cost-effective optical diagnostic for gas turbine combustor health monitoring. However, most chemical kinetics mechanisms of the chemiluminescence of target species such as OH*, CH*, and CO2* were developed from atmospheric-pressure data. The present paper presents a study wherein the ability of current kinetics models to predict the chemiluminescence trends at engine pressures was assessed. Shock-tube experiments were performed in highly diluted mixtures of H2/O2/Ar at a wide range of pressures to evaluate the ability of a current kinetics model to predict the measured trends. At elevated pressures up to 15 atm, the currently used reaction rate of H + O + M = OH* + M (i.e., without any pressure dependence) significantly over predicts the amount of OH* formed. Other important chemiluminescence species include CH* and CO2*, and separate experiments were performed to assess the validity of existing chemical kinetics mechanisms for both of these species at elevated pressures. A pressure excursion using methane-oxygen mixtures highly diluted in argon was performed up to about 15 atm, and the time histories of CH* and CO2* were measured over a range of temperatures from about 1700 to 2300 K. It was found that the existing CH* mechanism captured the T and P trends rather well, but the CO2* mechanism did a poor job of capturing both the temperature and pressure behavior. With respect to the modeling of collider species, it was found that the current OH* model performs well for N2, but some improvements can be made for CO2. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...] [article] Assessment of current chemiluminescence kinetics models at engine conditions [texte imprimé] / Eric Petersen, Auteur ; Madeleine Kopp, Auteur ; Nicole Donato, Auteur ; Felix Güthe, Auteur . - 2012 . - 07 p.
Génie mécanique
Langues : Anglais (eng)
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 07 p.
Mots-clés : Chemiluminescence Engines Gas turbines Reaction kinetics Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Chemiluminescence continues to be of interest as a cost-effective optical diagnostic for gas turbine combustor health monitoring. However, most chemical kinetics mechanisms of the chemiluminescence of target species such as OH*, CH*, and CO2* were developed from atmospheric-pressure data. The present paper presents a study wherein the ability of current kinetics models to predict the chemiluminescence trends at engine pressures was assessed. Shock-tube experiments were performed in highly diluted mixtures of H2/O2/Ar at a wide range of pressures to evaluate the ability of a current kinetics model to predict the measured trends. At elevated pressures up to 15 atm, the currently used reaction rate of H + O + M = OH* + M (i.e., without any pressure dependence) significantly over predicts the amount of OH* formed. Other important chemiluminescence species include CH* and CO2*, and separate experiments were performed to assess the validity of existing chemical kinetics mechanisms for both of these species at elevated pressures. A pressure excursion using methane-oxygen mixtures highly diluted in argon was performed up to about 15 atm, and the time histories of CH* and CO2* were measured over a range of temperatures from about 1700 to 2300 K. It was found that the existing CH* mechanism captured the T and P trends rather well, but the CO2* mechanism did a poor job of capturing both the temperature and pressure behavior. With respect to the modeling of collider species, it was found that the current OH* model performs well for N2, but some improvements can be made for CO2. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...]
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 14 p.
Titre : Displacement speed statistics for stratified mixture combustion in an igniting turbulent planar jet Type de document : texte imprimé Auteurs : Henrik Hesse, Auteur ; Sean P. Malkeson, Auteur ; Nilanjan Chakraborty, Auteur Année de publication : 2012 Article en page(s) : 14 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Flames Ignition Jets Statistics Stratified flow Turbulence Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The statistics of the density-weighted displacement speed of the reaction progress variable c isosurfaces for stratified mixture combustion arising from localized ignition in a turbulent planar coflowing jet have been studied based on 3D Direct Numerical Simulation data where the jet is considered to be fuel-rich and the coflow is taken to be fuel-lean. The resulting flame following successful ignition shows the premixed mode of combustion in fuel-rich and fuel-lean zones although an additional diffusion flame branch was also observed on the stoichiometric mixture isosurface at early times of flame evolution. The flame propagation characteristics have been analyzed in terms of the reaction, normal diffusion and tangential diffusion components of the density-weighted displacement speed for different values of reaction progress variables across the flame brush. It has been found that the reaction, normal diffusion and tangential diffusion components of density-weighted displacement speed, remain the major contributors to the density-weighted displacement speed at all stages of flame evolution as the magnitude of the component which originates due to mixture inhomogeneity remains negligible in comparison to the magnitudes of other components in accordance with previous experimental studies. It has been demonstrated that curvature and tangential strain rate dependences of the reaction progress variable gradient play key roles in determining strain rate dependences of the reaction and normal diffusion components of the density-weighted displacement speed. It has been shown that the interrelation between tangential strain rate and curvature affects the strain rate dependence of tangential diffusion component of the density-weighted displacement speed. The density-weighted displacement speed and curvature are found to be predominantly negatively correlated throughout the flame brush at all stages of the flame evolution. The relative strengths of the tangential strain rate dependence of the reaction, normal diffusion and tangential diffusion components of the density-weighted displacement speed ultimately determine the nature of correlation between the density-weighted displacement speed and the tangential strain rate. The strain rate and curvature dependences of the density-weighted displacement speed in stratified mixtures are found to be qualitatively similar to the statistics previously obtained for turbulent premixed flames. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...] [article] Displacement speed statistics for stratified mixture combustion in an igniting turbulent planar jet [texte imprimé] / Henrik Hesse, Auteur ; Sean P. Malkeson, Auteur ; Nilanjan Chakraborty, Auteur . - 2012 . - 14 p.
Génie mécanique
Langues : Anglais (eng)
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 14 p.
Mots-clés : Flames Ignition Jets Statistics Stratified flow Turbulence Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The statistics of the density-weighted displacement speed of the reaction progress variable c isosurfaces for stratified mixture combustion arising from localized ignition in a turbulent planar coflowing jet have been studied based on 3D Direct Numerical Simulation data where the jet is considered to be fuel-rich and the coflow is taken to be fuel-lean. The resulting flame following successful ignition shows the premixed mode of combustion in fuel-rich and fuel-lean zones although an additional diffusion flame branch was also observed on the stoichiometric mixture isosurface at early times of flame evolution. The flame propagation characteristics have been analyzed in terms of the reaction, normal diffusion and tangential diffusion components of the density-weighted displacement speed for different values of reaction progress variables across the flame brush. It has been found that the reaction, normal diffusion and tangential diffusion components of density-weighted displacement speed, remain the major contributors to the density-weighted displacement speed at all stages of flame evolution as the magnitude of the component which originates due to mixture inhomogeneity remains negligible in comparison to the magnitudes of other components in accordance with previous experimental studies. It has been demonstrated that curvature and tangential strain rate dependences of the reaction progress variable gradient play key roles in determining strain rate dependences of the reaction and normal diffusion components of the density-weighted displacement speed. It has been shown that the interrelation between tangential strain rate and curvature affects the strain rate dependence of tangential diffusion component of the density-weighted displacement speed. The density-weighted displacement speed and curvature are found to be predominantly negatively correlated throughout the flame brush at all stages of the flame evolution. The relative strengths of the tangential strain rate dependence of the reaction, normal diffusion and tangential diffusion components of the density-weighted displacement speed ultimately determine the nature of correlation between the density-weighted displacement speed and the tangential strain rate. The strain rate and curvature dependences of the density-weighted displacement speed in stratified mixtures are found to be qualitatively similar to the statistics previously obtained for turbulent premixed flames. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...]
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 07 p.
Titre : Fuel flexibility in LM2500 and LM6000 dry low emission engines Type de document : texte imprimé Auteurs : John Blouch, Auteur ; Hejie Li, Auteur ; Mark Mueller, Auteur ; Richard Hook, Auteur Année de publication : 2012 Article en page(s) : 07 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Aerospace engines Gas turbine Natural gas technology Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The LM2500 and LM6000 dry-low-emissions aeroderivative gas turbine engines have been in commercial service for 15 years and have accumulated nearly 10 × 106 hours of commercial operation. The majority of these engines utilize pipeline quality natural gas predominantly comprised of methane. There is; however, increasing interest in nonstandard fuels that contain varying levels of higher hydrocarbon species and/or inert gases. This paper reports on the demonstrated operability of LM2500 and LM6000 DLE engines with nonstandard fuels. In particular, rig tests at engine conditions were performed to demonstrate the robustness of the dual-annular counter-rotating swirlers premixer design, relative to flameholding with fuels containing high ethane, propane, and N2 concentrations. These experiments, which test the ability of the hardware to shed a flame introduced into the premixing region, have been used to expand the quoting limits for LM2500 and LM6000 gas turbine engines to elevated C2+ levels. In addition, chemical kinetics analysis was performed to understand the effect of temperature, pressure, and fuel compositions on flameholding. Test data for different fuels and operating conditions were successfully correlated with Damkohler number. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...] [article] Fuel flexibility in LM2500 and LM6000 dry low emission engines [texte imprimé] / John Blouch, Auteur ; Hejie Li, Auteur ; Mark Mueller, Auteur ; Richard Hook, Auteur . - 2012 . - 07 p.
Génie mécanique
Langues : Anglais (eng)
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 07 p.
Mots-clés : Aerospace engines Gas turbine Natural gas technology Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The LM2500 and LM6000 dry-low-emissions aeroderivative gas turbine engines have been in commercial service for 15 years and have accumulated nearly 10 × 106 hours of commercial operation. The majority of these engines utilize pipeline quality natural gas predominantly comprised of methane. There is; however, increasing interest in nonstandard fuels that contain varying levels of higher hydrocarbon species and/or inert gases. This paper reports on the demonstrated operability of LM2500 and LM6000 DLE engines with nonstandard fuels. In particular, rig tests at engine conditions were performed to demonstrate the robustness of the dual-annular counter-rotating swirlers premixer design, relative to flameholding with fuels containing high ethane, propane, and N2 concentrations. These experiments, which test the ability of the hardware to shed a flame introduced into the premixing region, have been used to expand the quoting limits for LM2500 and LM6000 gas turbine engines to elevated C2+ levels. In addition, chemical kinetics analysis was performed to understand the effect of temperature, pressure, and fuel compositions on flameholding. Test data for different fuels and operating conditions were successfully correlated with Damkohler number. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...]
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 10 p.
Titre : Dynamic-stability characteristics of premixed methane oxy-combustion Type de document : texte imprimé Auteurs : Andrew P. Shroll, Auteur ; Santosh J. Shanbhogue,, Auteur ; Ahmed F. Ghoniem, Auteur Année de publication : 2012 Article en page(s) : 10 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Combustion Flames Organic compounds Stability Stoichiometry Turbulence Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : This work explores the dynamic stability characteristics of premixed CH4/O2/CO2 mixtures in a 50 kW swirl stabilized combustor. In all cases, the methane-oxygen mixture is stoichiometric, with different dilution levels of carbon dioxide used to control the flame temperature (Tad). For the highest Tad's, the combustor is unstable at the first harmonic of the combustor's natural frequency. As the temperature is reduced, the combustor jumps to fundamental mode and then to a low-frequency mode whose value is well below the combustor's natural frequency, before eventually reaching blowoff. Similar to the case of CH4/air mixtures, the transition from one mode to another is predominantly a function of the Tad of the reactive mixture, despite significant differences in laminar burning velocity and/or strained flame consumption speed between air and oxy-fuel mixtures for a given Tad. High speed images support this finding by revealing similar vortex breakdown modes and thus similar turbulent flame geometries that change as a function of flame temperature. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...] [article] Dynamic-stability characteristics of premixed methane oxy-combustion [texte imprimé] / Andrew P. Shroll, Auteur ; Santosh J. Shanbhogue,, Auteur ; Ahmed F. Ghoniem, Auteur . - 2012 . - 10 p.
Génie mécanique
Langues : Anglais (eng)
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 10 p.
Mots-clés : Combustion Flames Organic compounds Stability Stoichiometry Turbulence Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : This work explores the dynamic stability characteristics of premixed CH4/O2/CO2 mixtures in a 50 kW swirl stabilized combustor. In all cases, the methane-oxygen mixture is stoichiometric, with different dilution levels of carbon dioxide used to control the flame temperature (Tad). For the highest Tad's, the combustor is unstable at the first harmonic of the combustor's natural frequency. As the temperature is reduced, the combustor jumps to fundamental mode and then to a low-frequency mode whose value is well below the combustor's natural frequency, before eventually reaching blowoff. Similar to the case of CH4/air mixtures, the transition from one mode to another is predominantly a function of the Tad of the reactive mixture, despite significant differences in laminar burning velocity and/or strained flame consumption speed between air and oxy-fuel mixtures for a given Tad. High speed images support this finding by revealing similar vortex breakdown modes and thus similar turbulent flame geometries that change as a function of flame temperature. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...]
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 11 p.
Titre : Passive control of noise and instability in a swirl-stabilized combustor with the use of high-strength porous insert Type de document : texte imprimé Auteurs : Daniel Sequera, Auteur ; Ajay K. Agrawal, Auteur Année de publication : 2012 Article en page(s) : 11 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Combustion Flames Foams Porous materials Turbulence Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Swirl-stabilized combustion and porous inert medium (PIM) combustion are two methods that have been used extensively, although independently, for flame stabilization. In this study, the two concepts are combined so that the porous insert serves as a passive device to mitigate combustion noise and instabilities. A properly shaped PIM is placed within the combustor to directly influence the turbulent flow field and vortical and/or shear layer structures associated with the outer recirculation zone and inner recirculation zone. After presenting the concept, the paper provides a conceptual understanding of the changes in the mean flow field caused by the PIM. Combustion experiments were conducted at atmospheric pressure using HfC/SiC coated open-cell foam structures of different pore sizes and shapes. Measurements of sound pressure level (SPL) and CO and NOx emissions were taken for different equivalence ratios and reactant flow rates. Combustion mode and PIM geometry to decrease the SPL are identified. The results show that the porous insert can reduce combustion noise without adversely affecting NOx and CO emissions. Experiments show that the proposed concept can also mitigate combustion instabilities encountered at high reactant flow rate. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...] [article] Passive control of noise and instability in a swirl-stabilized combustor with the use of high-strength porous insert [texte imprimé] / Daniel Sequera, Auteur ; Ajay K. Agrawal, Auteur . - 2012 . - 11 p.
Génie mécanique
Langues : Anglais (eng)
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 11 p.
Mots-clés : Combustion Flames Foams Porous materials Turbulence Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Swirl-stabilized combustion and porous inert medium (PIM) combustion are two methods that have been used extensively, although independently, for flame stabilization. In this study, the two concepts are combined so that the porous insert serves as a passive device to mitigate combustion noise and instabilities. A properly shaped PIM is placed within the combustor to directly influence the turbulent flow field and vortical and/or shear layer structures associated with the outer recirculation zone and inner recirculation zone. After presenting the concept, the paper provides a conceptual understanding of the changes in the mean flow field caused by the PIM. Combustion experiments were conducted at atmospheric pressure using HfC/SiC coated open-cell foam structures of different pore sizes and shapes. Measurements of sound pressure level (SPL) and CO and NOx emissions were taken for different equivalence ratios and reactant flow rates. Combustion mode and PIM geometry to decrease the SPL are identified. The results show that the porous insert can reduce combustion noise without adversely affecting NOx and CO emissions. Experiments show that the proposed concept can also mitigate combustion instabilities encountered at high reactant flow rate. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...]
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 08 p.
Titre : Hydroprocessed renewable jet fuel evaluation, performance, and emissions in a T63 turbine engine Type de document : texte imprimé Auteurs : C. D. Klingshirn, Auteur ; M. DeWitt, Auteur ; R. Striebich, Auteur Année de publication : 2012 Article en page(s) : 08 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Air pollution control Biofuel Combustion Environmental testing Jet engines Pyrolysis Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Due to potential beneficial environmental impacts and increased supply availability, alternative fuels derived from renewable resources are evolving on the forefront as unconventional substitutes for fossil fuel. Focus is being given to the evaluation and certification of Hydroprocessed Renewable Jet (HRJ), a fuel produced from animal fat and/or plant oils (triglycerides) by hydroprocessing, as the next potential synthetic aviation fuel. Extensive efforts have recently been performed at the Air Force Research Laboratory (AFRL) at Wright Patterson Air Force Base (WPAFB) to evaluate the potential of two HRJ fuels produced from camelina and tallow feedstocks. These have included characterization of the fuel chemical, physical fuel characteristics and Fit-for-Purpose properties (FFP). The present effort describes general combustion performance and the emission propensity of a T63-A-700 Allison turbine engine operated on the HRJs and 50/50 (by volume) HRJ/JP-8 fuel blends relative to a specification JP-8. In addition, engine and emission testing with a blend of the tallow-derived HRJ and 16% bio-derived aromatic components was completed. Fundamental engine performance characterization allows for determination of the suitability of potential synthetic fuels while quantitation of gaseous and particulate matter emissions provides an assessment of the potential environmental impact compared to current petroleum-derived fuels. In addition, an extended 150 h endurance test was performed using a 50/50 blend of tallow-derived HRJ with JP-8 to evaluate the long-term operation of the engine with the synthetic fuel blend. This paper discusses the laboratory testing performed to characterize HRJs and results from the basic engine operability and emissions studies of the alternative fuel blends. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...] [article] Hydroprocessed renewable jet fuel evaluation, performance, and emissions in a T63 turbine engine [texte imprimé] / C. D. Klingshirn, Auteur ; M. DeWitt, Auteur ; R. Striebich, Auteur . - 2012 . - 08 p.
Génie mécanique
Langues : Anglais (eng)
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 08 p.
Mots-clés : Air pollution control Biofuel Combustion Environmental testing Jet engines Pyrolysis Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Due to potential beneficial environmental impacts and increased supply availability, alternative fuels derived from renewable resources are evolving on the forefront as unconventional substitutes for fossil fuel. Focus is being given to the evaluation and certification of Hydroprocessed Renewable Jet (HRJ), a fuel produced from animal fat and/or plant oils (triglycerides) by hydroprocessing, as the next potential synthetic aviation fuel. Extensive efforts have recently been performed at the Air Force Research Laboratory (AFRL) at Wright Patterson Air Force Base (WPAFB) to evaluate the potential of two HRJ fuels produced from camelina and tallow feedstocks. These have included characterization of the fuel chemical, physical fuel characteristics and Fit-for-Purpose properties (FFP). The present effort describes general combustion performance and the emission propensity of a T63-A-700 Allison turbine engine operated on the HRJs and 50/50 (by volume) HRJ/JP-8 fuel blends relative to a specification JP-8. In addition, engine and emission testing with a blend of the tallow-derived HRJ and 16% bio-derived aromatic components was completed. Fundamental engine performance characterization allows for determination of the suitability of potential synthetic fuels while quantitation of gaseous and particulate matter emissions provides an assessment of the potential environmental impact compared to current petroleum-derived fuels. In addition, an extended 150 h endurance test was performed using a 50/50 blend of tallow-derived HRJ with JP-8 to evaluate the long-term operation of the engine with the synthetic fuel blend. This paper discusses the laboratory testing performed to characterize HRJs and results from the basic engine operability and emissions studies of the alternative fuel blends. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...]
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 08 p.
Titre : Application of pseudo-poincaré maps to assess gas turbine system health Type de document : texte imprimé Auteurs : Hany Bassily, Auteur ; Mohammed F. Daqaq, Auteur ; John Wagner, Auteur Année de publication : 2012 Article en page(s) : 08 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Condition monitoring Gas turbines Maintenance engineering erformance evaluation Power generation reliability Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The transition between two operational modes in a dynamic system often occurs under strict measures such that repeatability is more a target than a metric for performance evaluations. The concept of Poincaré maps may be applied to health monitoring systems. In this paper, a diagnosis strategy based on Poincaré maps will be presented to evaluate dynamic systems' behavior with application to power generating gas turbines based on the repeatability of the transition trajectories. Using this approach, extensive operating data for three 85 MW simple cycle power generating gas turbines were evaluated to assess and analyze their performance. The proposed strategy was capable of isolating failed starts; automatic unloads and load rejection events as major events during the test period. Results and conclusions drawn in this study regarding the health condition of the rotating equipment demonstrate the opportunity for system monitoring. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...] [article] Application of pseudo-poincaré maps to assess gas turbine system health [texte imprimé] / Hany Bassily, Auteur ; Mohammed F. Daqaq, Auteur ; John Wagner, Auteur . - 2012 . - 08 p.
Génie mécanique
Langues : Anglais (eng)
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 08 p.
Mots-clés : Condition monitoring Gas turbines Maintenance engineering erformance evaluation Power generation reliability Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The transition between two operational modes in a dynamic system often occurs under strict measures such that repeatability is more a target than a metric for performance evaluations. The concept of Poincaré maps may be applied to health monitoring systems. In this paper, a diagnosis strategy based on Poincaré maps will be presented to evaluate dynamic systems' behavior with application to power generating gas turbines based on the repeatability of the transition trajectories. Using this approach, extensive operating data for three 85 MW simple cycle power generating gas turbines were evaluated to assess and analyze their performance. The proposed strategy was capable of isolating failed starts; automatic unloads and load rejection events as major events during the test period. Results and conclusions drawn in this study regarding the health condition of the rotating equipment demonstrate the opportunity for system monitoring. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...]
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 08 p.
Titre : Experimental and analytical study on the operation characteristics of the AHAT system Type de document : texte imprimé Auteurs : Hidefumi Araki, Auteur ; Tomomi Koganezawa, Auteur ; Chihiro Myouren, Auteur Année de publication : 2012 Article en page(s) : 08 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Combined cycle power stations Gas turbines Heat transfer Humidity Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Operational flexibility, such as faster start-up time or faster load change rate, and higher thermal efficiency, have become more and more important for recent thermal power systems. The advanced humid air turbine (AHAT) system has been studied to improve operational flexibility and thermal efficiency of the gas turbine power generation system. Advanced humid air turbine is an original system which substitutes the water atomization cooling (WAC) system for the intercooler system of the HAT cycle. A 3 MW pilot plant, which is composed of a gas turbine, a humidification tower, a recuperator and a water recovery system, was built in 2006 to verify feasibility of the AHAT system.In this paper, ambient temperature effects, part-load characteristics and start-up characteristics of the AHAT system were studied both experimentally and analytically. Also, change in heat transfer characteristics of the recuperator of the 3 MW pilot plant was evaluated from Nov. 2006 to Feb. 2010. Ambient temperature effects and part-load characteristics of the 3 MW pilot plant were compared with heat and material balance calculation results. Then, these characteristics of the AHAT and the combined cycle (CC) systems were compared assuming they were composed of mid-sized industrial gas turbines.The measured cold start-up time of the 3 MW AHAT pilot plant was about 60 min, which was dominated by the heat capacities of the plant equipment. The gas turbine was operated a total of 34 times during this period (Nov. 2006 to Feb. 2010), but no interannual changes were observed in pressure drops, temperature effectiveness, and the overall heat transfer coefficient of the recuperator. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...] [article] Experimental and analytical study on the operation characteristics of the AHAT system [texte imprimé] / Hidefumi Araki, Auteur ; Tomomi Koganezawa, Auteur ; Chihiro Myouren, Auteur . - 2012 . - 08 p.
Génie mécanique
Langues : Anglais (eng)
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 08 p.
Mots-clés : Combined cycle power stations Gas turbines Heat transfer Humidity Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Operational flexibility, such as faster start-up time or faster load change rate, and higher thermal efficiency, have become more and more important for recent thermal power systems. The advanced humid air turbine (AHAT) system has been studied to improve operational flexibility and thermal efficiency of the gas turbine power generation system. Advanced humid air turbine is an original system which substitutes the water atomization cooling (WAC) system for the intercooler system of the HAT cycle. A 3 MW pilot plant, which is composed of a gas turbine, a humidification tower, a recuperator and a water recovery system, was built in 2006 to verify feasibility of the AHAT system.In this paper, ambient temperature effects, part-load characteristics and start-up characteristics of the AHAT system were studied both experimentally and analytically. Also, change in heat transfer characteristics of the recuperator of the 3 MW pilot plant was evaluated from Nov. 2006 to Feb. 2010. Ambient temperature effects and part-load characteristics of the 3 MW pilot plant were compared with heat and material balance calculation results. Then, these characteristics of the AHAT and the combined cycle (CC) systems were compared assuming they were composed of mid-sized industrial gas turbines.The measured cold start-up time of the 3 MW AHAT pilot plant was about 60 min, which was dominated by the heat capacities of the plant equipment. The gas turbine was operated a total of 34 times during this period (Nov. 2006 to Feb. 2010), but no interannual changes were observed in pressure drops, temperature effectiveness, and the overall heat transfer coefficient of the recuperator. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...]
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 07 p.
Titre : The expansion-cycle evaporation turbine Type de document : texte imprimé Auteurs : N. G. Barton, Auteur Année de publication : 2012 Article en page(s) : 07 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Cooling Fans Gas turbines Heat engines Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : This paper investigates a continuous-flow heat engine based on evaporative cooling of hot air at reduced pressure. In this device, hot air is expanded in an expansion turbine, spray-cooled to saturation and re-compressed to ambient pressure in several stages with evaporative cooling between each stage. More work is available in expansion than is required during re-compression, so the device is a heat engine. The device provides a relatively cheap way to boost the power output of open-cycle gas turbines. The principal assumptions for the theoretical model developed herein are that air and water vapor are regarded as ideal gases with constant specific heat capacities. In the absence of losses associated with expansion and compression, the engine produces more power as the inlet temperature and the pressure ratio increase. The effects of irreversibilities are subsequently included in the expansion and compression stages, with realistic values used for the adiabatic efficiencies of turbine and fans. Purification and injection of water are also considered in the overall energy budget. As a typical result for the new engine, if the inlet air is the exhaust of a 56 MW open-cycle gas turbine, the adiabatic efficiencies of turbine and fan are 0.9, the pressure ratio is 6.5 and there is four-stage re-compression, then the power output is 20.5% that of the gas turbine. The power output is sensitive to the adiabatic efficiencies of turbine and fans. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...] [article] The expansion-cycle evaporation turbine [texte imprimé] / N. G. Barton, Auteur . - 2012 . - 07 p.
Génie mécanique
Langues : Anglais (eng)
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 07 p.
Mots-clés : Cooling Fans Gas turbines Heat engines Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : This paper investigates a continuous-flow heat engine based on evaporative cooling of hot air at reduced pressure. In this device, hot air is expanded in an expansion turbine, spray-cooled to saturation and re-compressed to ambient pressure in several stages with evaporative cooling between each stage. More work is available in expansion than is required during re-compression, so the device is a heat engine. The device provides a relatively cheap way to boost the power output of open-cycle gas turbines. The principal assumptions for the theoretical model developed herein are that air and water vapor are regarded as ideal gases with constant specific heat capacities. In the absence of losses associated with expansion and compression, the engine produces more power as the inlet temperature and the pressure ratio increase. The effects of irreversibilities are subsequently included in the expansion and compression stages, with realistic values used for the adiabatic efficiencies of turbine and fans. Purification and injection of water are also considered in the overall energy budget. As a typical result for the new engine, if the inlet air is the exhaust of a 56 MW open-cycle gas turbine, the adiabatic efficiencies of turbine and fan are 0.9, the pressure ratio is 6.5 and there is four-stage re-compression, then the power output is 20.5% that of the gas turbine. The power output is sensitive to the adiabatic efficiencies of turbine and fans. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...]
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 08 p.
Titre : Compressor fouling modeling : relationship between computational roughness and gas turbine operation time Type de document : texte imprimé Auteurs : Francesco Melino, Auteur ; Mirko Morini, Auteur ; Antonio Peretto, Auteur Année de publication : 2012 Article en page(s) : 08 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Blades Compressors Computational fluid dynamics Gas turbines Surface roughness Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Gas turbine axial compressor performance is heavily influenced by blade fouling. As a result, the gas turbines efficiency and producible power output decrease. Performance degradation of an axial compressor stage due to fouling can be analyzed by means of simulation through computational fluid dynamics (CFD) codes. Usually these methods reproduce the deteriorated blades by increasing their surface roughness and thickness. Another approach is the scaling of compressor stage performance maps. A model based on stage-by-stage techniques was presented in a previous work. This model is able to estimate the modifications of the overall compressor performance map as a function of the operating hours. The aim of the present study is to combine these two different approaches in order to relate the increase of blade computational surface roughness with compressor operating hours. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...] [article] Compressor fouling modeling : relationship between computational roughness and gas turbine operation time [texte imprimé] / Francesco Melino, Auteur ; Mirko Morini, Auteur ; Antonio Peretto, Auteur . - 2012 . - 08 p.
Génie mécanique
Langues : Anglais (eng)
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 08 p.
Mots-clés : Blades Compressors Computational fluid dynamics Gas turbines Surface roughness Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Gas turbine axial compressor performance is heavily influenced by blade fouling. As a result, the gas turbines efficiency and producible power output decrease. Performance degradation of an axial compressor stage due to fouling can be analyzed by means of simulation through computational fluid dynamics (CFD) codes. Usually these methods reproduce the deteriorated blades by increasing their surface roughness and thickness. Another approach is the scaling of compressor stage performance maps. A model based on stage-by-stage techniques was presented in a previous work. This model is able to estimate the modifications of the overall compressor performance map as a function of the operating hours. The aim of the present study is to combine these two different approaches in order to relate the increase of blade computational surface roughness with compressor operating hours. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...]
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 13 p.
Titre : Extended three-dimensional thermo-hydrodynamic model of radial foil bearing : case studies on thermal behaviors and dynamic characteristics in gas turbine simulator Type de document : texte imprimé Auteurs : Daejong Kim, Auteur ; Jeongpill Ki, Auteur ; Youngcheol Kim, Auteur Année de publication : 2012 Article en page(s) : 13 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Computational fluid dynamics Cooling Damping Elasticity Gas turbine power stations Gas turbines Hydrodynamics Impellers Machine bearings Perturbation techniques Rotors Shafts Small electric machines Softening Thermal resistance Viscosity Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Environment-friendly microturbomachinery has its broad current and future applications in fuel cells, power generation, oil-free industrial blowers and compressors, small aero propulsions engines for missiles and small aircrafts, automotive turbo chargers, etc. Air foil bearings (AFBs) have been one of the popular subjects in recent years due to ever-growing interests in the environment-friendly oil-free turbomachinery. AFBs have many noticeable attractive features compared to conventional rigid-walled air/gas bearings such as improved damping and tolerance to minor shaft misalignment and external shocks. In addition, the low viscosity of air or gas allows very low power consumption even at high speeds. A turbine simulator mimicking 50 kW power generation gas turbine was designed. The turbine simulator can generate the same thermodynamic conditions and axial thrust load as the actual gas turbine. In this paper, the 3-D thermo-hydrodynamic (THD) model developed for single radial AFB was further extended to the turbine simulator configuration by extending the solution domain to the surrounding structures including two plenums, bearing sleeve, housing, and rotor exposed to the plenums. In addition, a computational fluid dynamic (CFD) model on the leading edge groove region was developed for better prediction of inlet thermal boundary conditions for the bearing. Several case studies are presented through computer simulations for hydrodynamically preloaded three-pad radial AFB in the hot section. It is found that both bearing and rotor should be provided with cooling air to maintain the temperature of both the rotor and top foil below 300 °C. It is also found that the higher thermal contact resistance between the rotor and hot impellers reduces the axial temperature gradient of the rotor. Dynamic performance of the bearing was evaluated using the linear perturbation method for operation at elevated temperature. The softening effect of the bump foil at elevated temperature results in a decrease of both stiffness and damping coefficients compared to the values at room temperature. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...] [article] Extended three-dimensional thermo-hydrodynamic model of radial foil bearing : case studies on thermal behaviors and dynamic characteristics in gas turbine simulator [texte imprimé] / Daejong Kim, Auteur ; Jeongpill Ki, Auteur ; Youngcheol Kim, Auteur . - 2012 . - 13 p.
Génie mécanique
Langues : Anglais (eng)
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 13 p.
Mots-clés : Computational fluid dynamics Cooling Damping Elasticity Gas turbine power stations Gas turbines Hydrodynamics Impellers Machine bearings Perturbation techniques Rotors Shafts Small electric machines Softening Thermal resistance Viscosity Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Environment-friendly microturbomachinery has its broad current and future applications in fuel cells, power generation, oil-free industrial blowers and compressors, small aero propulsions engines for missiles and small aircrafts, automotive turbo chargers, etc. Air foil bearings (AFBs) have been one of the popular subjects in recent years due to ever-growing interests in the environment-friendly oil-free turbomachinery. AFBs have many noticeable attractive features compared to conventional rigid-walled air/gas bearings such as improved damping and tolerance to minor shaft misalignment and external shocks. In addition, the low viscosity of air or gas allows very low power consumption even at high speeds. A turbine simulator mimicking 50 kW power generation gas turbine was designed. The turbine simulator can generate the same thermodynamic conditions and axial thrust load as the actual gas turbine. In this paper, the 3-D thermo-hydrodynamic (THD) model developed for single radial AFB was further extended to the turbine simulator configuration by extending the solution domain to the surrounding structures including two plenums, bearing sleeve, housing, and rotor exposed to the plenums. In addition, a computational fluid dynamic (CFD) model on the leading edge groove region was developed for better prediction of inlet thermal boundary conditions for the bearing. Several case studies are presented through computer simulations for hydrodynamically preloaded three-pad radial AFB in the hot section. It is found that both bearing and rotor should be provided with cooling air to maintain the temperature of both the rotor and top foil below 300 °C. It is also found that the higher thermal contact resistance between the rotor and hot impellers reduces the axial temperature gradient of the rotor. Dynamic performance of the bearing was evaluated using the linear perturbation method for operation at elevated temperature. The softening effect of the bump foil at elevated temperature results in a decrease of both stiffness and damping coefficients compared to the values at room temperature. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...]
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 11 p.
Titre : Computational fluid dynamics simulations of flow and heat transfer in a preswirl system : influence of rotating-stationary domain interface Type de document : texte imprimé Auteurs : Joachim Karnahl, Auteur ; Jens von Wolfersdorf, Auteur ; Kok-Mun Tham, Auteur Année de publication : 2012 Article en page(s) : 11 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Computational fluid dynamics Coriolis force Flow instability Flow simulation Heat transfer Jets Nozzles Rotors Stators Swirling flow Turbulence Résumé : This paper presents computational fluid dynamics (CFD) predictions of flow and heat transfer for an over-swirled low-radius preswirl system and comparison with experimental data. The rotor-stator CFD model comprises a stationary domain with the preswirl nozzles and a rotating domain with the receiver holes. The fluid-dynamic conditions feature an over-swirled system with a swirl ratio at the nozzle radius betap = 1.4−1.5 and rotational Reynolds number RePhi = 0.8 × 106 and 1.2 × 106. Three different treatments for the rotating and stationary domain interface are used to evaluate the influence on the flow and heat transfer behavior: a stationary approach (including Coriolis forces in the rotating domain) with “direct connection” and fixed angle between preswirl nozzle and receiver holes; a stationary approach with circumferential averaging of the velocity at radial bands; and a full transient simulation with the rotating domain capturing the unsteady flow due to the rotating receiver holes. Results at different circumferential angles show high variability in pressure and velocity distributions at the preswirl inlet nozzle radius. Circumferential averaging of these flow parameters lead to an alignment of the pressures and velocities between the three different interface approaches. Comparison with experimental pressure and swirl-ratio data show a quantitative agreement but the CFD results feature a systematic overestimation outward of the preswirl nozzle radius. Heat transfer coefficient distributions at the rotor surface show the effect of the different interface approaches and dependence on the flow structure (for example the impinging jet and vortex structures). The three different interface approaches result in significant differences in the computed heat transfer coefficients between pairs of receiver holes. Circumferentially averaged heat transfer coefficients inward of the receiver holes radius show good agreement between the transient and stationary direct connection interfaces, whereas those for the circumferential averaging interface differ, contrary to the flow parameters, due to smoothing of local effects from the preswirl jets. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...] [article] Computational fluid dynamics simulations of flow and heat transfer in a preswirl system : influence of rotating-stationary domain interface [texte imprimé] / Joachim Karnahl, Auteur ; Jens von Wolfersdorf, Auteur ; Kok-Mun Tham, Auteur . - 2012 . - 11 p.
Génie mécanique
Langues : Anglais (eng)
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 11 p.
Mots-clés : Computational fluid dynamics Coriolis force Flow instability Flow simulation Heat transfer Jets Nozzles Rotors Stators Swirling flow Turbulence Résumé : This paper presents computational fluid dynamics (CFD) predictions of flow and heat transfer for an over-swirled low-radius preswirl system and comparison with experimental data. The rotor-stator CFD model comprises a stationary domain with the preswirl nozzles and a rotating domain with the receiver holes. The fluid-dynamic conditions feature an over-swirled system with a swirl ratio at the nozzle radius betap = 1.4−1.5 and rotational Reynolds number RePhi = 0.8 × 106 and 1.2 × 106. Three different treatments for the rotating and stationary domain interface are used to evaluate the influence on the flow and heat transfer behavior: a stationary approach (including Coriolis forces in the rotating domain) with “direct connection” and fixed angle between preswirl nozzle and receiver holes; a stationary approach with circumferential averaging of the velocity at radial bands; and a full transient simulation with the rotating domain capturing the unsteady flow due to the rotating receiver holes. Results at different circumferential angles show high variability in pressure and velocity distributions at the preswirl inlet nozzle radius. Circumferential averaging of these flow parameters lead to an alignment of the pressures and velocities between the three different interface approaches. Comparison with experimental pressure and swirl-ratio data show a quantitative agreement but the CFD results feature a systematic overestimation outward of the preswirl nozzle radius. Heat transfer coefficient distributions at the rotor surface show the effect of the different interface approaches and dependence on the flow structure (for example the impinging jet and vortex structures). The three different interface approaches result in significant differences in the computed heat transfer coefficients between pairs of receiver holes. Circumferentially averaged heat transfer coefficients inward of the receiver holes radius show good agreement between the transient and stationary direct connection interfaces, whereas those for the circumferential averaging interface differ, contrary to the flow parameters, due to smoothing of local effects from the preswirl jets. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...]
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 07 p.
Titre : The effect of tilting pad journal bearing dynamic models on the linear stability analysis of an 8-stage compressor Type de document : texte imprimé Auteurs : Timothy W. Dimond, Auteur ; Amir A. Younan, Auteur ; Paul Allaire, Auteur Année de publication : 2012 Article en page(s) : 07 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Compressors Gas turbines Machine bearings Rotors Vibration measurement Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Rotordynamic instability, a self-excited vibration phenomenon, can lead to equipment failures, reduced production rates, and expensive redesign. Properly characterizing the stability response of flexible rotors on tilting pad bearings is therefore vital. Typically, this must be first considered during the design stage with computer modeling. Previous studies have demonstrated that non-synchronous bearing coefficients give a lower estimate of bearing stability than the eight synchronously reduced tiling pad bearing coefficients. However, a study of a reduced order non-synchronous stiffness-damping-mass (KCM) model and the effect on stability estimates has not been done previously for the same rotor model. In this paper, four load-between-pad tilting pad bearing designs, two four-pad and two five-pad, are considered. The stability margin for an eight-stage gas reinjection compressor is estimated for the four bearings, using a full KC representation, the KCM representation, and synchronously reduced bearing coefficients. The full KC representation gave the lowest estimate of stability margin, with up to 18% difference between full KC and KCM and up to 109% difference between full KC and synchronously reduced bearing coefficients. The results indicate that the KCM bearing representation does not necessarily result in the lowest estimate of rotordynamic stability margin, which is of significant interest to rotating machinery designers. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...] [article] The effect of tilting pad journal bearing dynamic models on the linear stability analysis of an 8-stage compressor [texte imprimé] / Timothy W. Dimond, Auteur ; Amir A. Younan, Auteur ; Paul Allaire, Auteur . - 2012 . - 07 p.
Génie mécanique
Langues : Anglais (eng)
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 07 p.
Mots-clés : Compressors Gas turbines Machine bearings Rotors Vibration measurement Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Rotordynamic instability, a self-excited vibration phenomenon, can lead to equipment failures, reduced production rates, and expensive redesign. Properly characterizing the stability response of flexible rotors on tilting pad bearings is therefore vital. Typically, this must be first considered during the design stage with computer modeling. Previous studies have demonstrated that non-synchronous bearing coefficients give a lower estimate of bearing stability than the eight synchronously reduced tiling pad bearing coefficients. However, a study of a reduced order non-synchronous stiffness-damping-mass (KCM) model and the effect on stability estimates has not been done previously for the same rotor model. In this paper, four load-between-pad tilting pad bearing designs, two four-pad and two five-pad, are considered. The stability margin for an eight-stage gas reinjection compressor is estimated for the four bearings, using a full KC representation, the KCM representation, and synchronously reduced bearing coefficients. The full KC representation gave the lowest estimate of stability margin, with up to 18% difference between full KC and KCM and up to 109% difference between full KC and synchronously reduced bearing coefficients. The results indicate that the KCM bearing representation does not necessarily result in the lowest estimate of rotordynamic stability margin, which is of significant interest to rotating machinery designers. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...]
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 08 p.
Titre : Numerical characterization of aerodynamic losses of jet arrays for gas turbine applications Type de document : texte imprimé Auteurs : Antonio Andreini, Auteur ; Riccardo Da Soghe, Auteur Année de publication : 2012 Article en page(s) : 08 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Aerodynamics Blades Computational fluid dynamics Cooling Gas turbines Jets Navier-Stokes equations Numerical analysis Turbulence Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Jet array is an arrangement typically used to cool several gas turbine parts. Some examples of such applications can be found in the impingement cooled region of gas turbine airfoils or in the turbine blade tip clearances control of large aero-engines. In order to correctly evaluate the impinging jet mass flow rate, the characterization of holes discharge coefficient is a compulsory activity. In this work, an aerodynamic analysis of jet arrays for active clearance control was performed; the aim was the definition of a correlation for the discharge coefficient (Cd) of a generic hole of the array. The data were taken from a set of CFD RANS simulations, in which the behavior of the cooling system was investigated over a wide range of fluid-dynamics conditions. Furthermore, several different holes arrangements were investigated in significant detail, with the aim of evaluating the influence of the hole spacing on the discharge coefficient distribution. Tests were conducted by varying the jet Reynolds number in a wide range of effective engine operative conditions (Re = 2000-12,000, Pressure- Ratio = 1.01-1.6). To point out the reliability of the CFD analysis, some comparisons with experimental data, measured at the Department of Energy Engineering of the University of Florence, were drawn. An in-depth analysis of the numerical data set has underlined the opportunity of an efficient reduction through the mass velocity ratio of hole and feeding pipe: the dependence of the discharge coefficients from this parameter is roughly logarithmic. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...] [article] Numerical characterization of aerodynamic losses of jet arrays for gas turbine applications [texte imprimé] / Antonio Andreini, Auteur ; Riccardo Da Soghe, Auteur . - 2012 . - 08 p.
Génie mécanique
Langues : Anglais (eng)
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 08 p.
Mots-clés : Aerodynamics Blades Computational fluid dynamics Cooling Gas turbines Jets Navier-Stokes equations Numerical analysis Turbulence Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Jet array is an arrangement typically used to cool several gas turbine parts. Some examples of such applications can be found in the impingement cooled region of gas turbine airfoils or in the turbine blade tip clearances control of large aero-engines. In order to correctly evaluate the impinging jet mass flow rate, the characterization of holes discharge coefficient is a compulsory activity. In this work, an aerodynamic analysis of jet arrays for active clearance control was performed; the aim was the definition of a correlation for the discharge coefficient (Cd) of a generic hole of the array. The data were taken from a set of CFD RANS simulations, in which the behavior of the cooling system was investigated over a wide range of fluid-dynamics conditions. Furthermore, several different holes arrangements were investigated in significant detail, with the aim of evaluating the influence of the hole spacing on the discharge coefficient distribution. Tests were conducted by varying the jet Reynolds number in a wide range of effective engine operative conditions (Re = 2000-12,000, Pressure- Ratio = 1.01-1.6). To point out the reliability of the CFD analysis, some comparisons with experimental data, measured at the Department of Energy Engineering of the University of Florence, were drawn. An in-depth analysis of the numerical data set has underlined the opportunity of an efficient reduction through the mass velocity ratio of hole and feeding pipe: the dependence of the discharge coefficients from this parameter is roughly logarithmic. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...]
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 11. p.
Titre : Measured static and rotordynamic coefficient results for a rocker-pivot, tilting-pad bearing with 50 and 60% offsets Type de document : texte imprimé Auteurs : Chris D. Kulhanek, Auteur ; Childs, Dara W., Auteur Année de publication : 2012 Article en page(s) : 11. p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Damping Dynamic testing Elasticity Machine bearings Rotors Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Static and rotordynamic coefficients are measured for a rocker-pivot, tilting-pad journal bearing (TPJB) with 50 and 60% offset pads in a load-between-pad (LBP) configuration. The bearing uses leading-edge-groove direct lubrication and has the following characteristics: 5-pads, 101.6 mm (4.0 in) nominal diameter,0.0814 -0.0837 mm (0.0032–0.0033 in) radial bearing clearance, 0.25 to 0.27 preload, and 60.325 mm (2.375 in) axial pad length. Tests were performed on a floating bearing test rig with unit loads from 0 to 3101 kPa (450 psi) and speeds from 7 to 16 krpm. Dynamic tests were conducted over a range of frequencies (20 to 320 Hz) to obtain complex dynamic stiffness coefficients as functions of excitation frequency. For most test conditions, the real dynamic stiffness functions were well fitted with a quadratic function with respect to frequency. This curve fit allowed for the stiffness frequency dependency to be captured by including an added mass matrix [M] to a conventional [K][C] model, yielding a frequency independent [K][C][M] model. The imaginary dynamic stiffness coefficients increased linearly with frequency, producing frequency-independent direct damping coefficients. Direct stiffness coefficients were larger for the 60% offset bearing at light unit loads. At high loads, the 50% offset configuration had a larger stiffness in the loaded direction, while the unloaded direct stiffness was approximately the same for both pivot offsets. Cross-coupled stiffness coefficients were positive and significantly smaller than direct stiffness coefficients. Negative direct added-mass coefficients were obtained for both offsets, especially in the unloaded direction. Cross-coupled added-mass coefficients are generally positive and of the same sign. Direct damping coefficients were mostly independent of load and speed, showing no appreciable difference between pivot offsets. Cross-coupled damping coefficients had the same sign and were much smaller than direct coefficients. Measured static eccentricities suggested cross coupling stiffness exists for both pivot offsets, agreeing with dynamic measurements. Static stiffness measurements showed good agreement with the loaded, direct dynamic stiffness coefficients. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...] [article] Measured static and rotordynamic coefficient results for a rocker-pivot, tilting-pad bearing with 50 and 60% offsets [texte imprimé] / Chris D. Kulhanek, Auteur ; Childs, Dara W., Auteur . - 2012 . - 11. p.
Génie mécanique
Langues : Anglais (eng)
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 11. p.
Mots-clés : Damping Dynamic testing Elasticity Machine bearings Rotors Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Static and rotordynamic coefficients are measured for a rocker-pivot, tilting-pad journal bearing (TPJB) with 50 and 60% offset pads in a load-between-pad (LBP) configuration. The bearing uses leading-edge-groove direct lubrication and has the following characteristics: 5-pads, 101.6 mm (4.0 in) nominal diameter,0.0814 -0.0837 mm (0.0032–0.0033 in) radial bearing clearance, 0.25 to 0.27 preload, and 60.325 mm (2.375 in) axial pad length. Tests were performed on a floating bearing test rig with unit loads from 0 to 3101 kPa (450 psi) and speeds from 7 to 16 krpm. Dynamic tests were conducted over a range of frequencies (20 to 320 Hz) to obtain complex dynamic stiffness coefficients as functions of excitation frequency. For most test conditions, the real dynamic stiffness functions were well fitted with a quadratic function with respect to frequency. This curve fit allowed for the stiffness frequency dependency to be captured by including an added mass matrix [M] to a conventional [K][C] model, yielding a frequency independent [K][C][M] model. The imaginary dynamic stiffness coefficients increased linearly with frequency, producing frequency-independent direct damping coefficients. Direct stiffness coefficients were larger for the 60% offset bearing at light unit loads. At high loads, the 50% offset configuration had a larger stiffness in the loaded direction, while the unloaded direct stiffness was approximately the same for both pivot offsets. Cross-coupled stiffness coefficients were positive and significantly smaller than direct stiffness coefficients. Negative direct added-mass coefficients were obtained for both offsets, especially in the unloaded direction. Cross-coupled added-mass coefficients are generally positive and of the same sign. Direct damping coefficients were mostly independent of load and speed, showing no appreciable difference between pivot offsets. Cross-coupled damping coefficients had the same sign and were much smaller than direct coefficients. Measured static eccentricities suggested cross coupling stiffness exists for both pivot offsets, agreeing with dynamic measurements. Static stiffness measurements showed good agreement with the loaded, direct dynamic stiffness coefficients. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...]
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 07 p.
Titre : Estimating the probabilistic size and shape distributions of 3D anomalies from sectioning measurements using the stereological unfolding approach Type de document : texte imprimé Auteurs : Wuwei Liang, Auteur ; Enright, Michael P., Auteur Année de publication : 2012 Article en page(s) : 07 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Risk management Rotors Spheroidizing Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The accuracy of probabilistic risk assessment of rotor disks is strongly dependent on the accurate description of the size and shape distributions of anomalies in alloys. These size-shape distributions of anomalies are often derived from planar sectioning data measurements using stereological unfolding algorithms. Since it is impossible to accurately predict the shape and orientation parameters of a general ellipsoid based on measurements obtained from two-dimensional sectioning data, the anomaly model should be limited to a spheroid. In this study, an unfolding algorithm was implemented and verified that can be used to estimate the probabilistic dimensions and orientations of 3D spheroids based on 2D section data. It is shown that the accuracy of the predicted spheroid model is dependent on the number of sections and the discretization of the mesh used to characterize the data. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...] [article] Estimating the probabilistic size and shape distributions of 3D anomalies from sectioning measurements using the stereological unfolding approach [texte imprimé] / Wuwei Liang, Auteur ; Enright, Michael P., Auteur . - 2012 . - 07 p.
Génie mécanique
Langues : Anglais (eng)
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 07 p.
Mots-clés : Risk management Rotors Spheroidizing Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The accuracy of probabilistic risk assessment of rotor disks is strongly dependent on the accurate description of the size and shape distributions of anomalies in alloys. These size-shape distributions of anomalies are often derived from planar sectioning data measurements using stereological unfolding algorithms. Since it is impossible to accurately predict the shape and orientation parameters of a general ellipsoid based on measurements obtained from two-dimensional sectioning data, the anomaly model should be limited to a spheroid. In this study, an unfolding algorithm was implemented and verified that can be used to estimate the probabilistic dimensions and orientations of 3D spheroids based on 2D section data. It is shown that the accuracy of the predicted spheroid model is dependent on the number of sections and the discretization of the mesh used to characterize the data. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...]
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 09 p.
Titre : Analytic modeling of floating ring annular seals Type de document : texte imprimé Auteurs : Arghir, Mihai, Auteur ; Manh-Hung Nguyen, Auteur ; David Tonon, Auteur Année de publication : 2012 Article en page(s) : 09 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Chaos Friction Hydrodynamics Impact (mechanical) Rings (structures) Rotors Seals (stoppers) Stators Vibrations Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : In order to avoid contact between the vibrating rotor and the stator, annular seals are designed with a relatively large radial clearance (~100 µm) and, therefore, have an important leakage. The floating ring annular seal is able to reduce the leakage flow rate by using a much lower clearance. The seal is designed as a ring floating on the rotor in order to accommodate its vibrations. The pressure difference between the upstream and the downstream chambers is pressing the nose of the floating ring (secondary seal) against the stator. The forces acting on the floating ring are the resultant of the hydrodynamic pressure field inside the primary seal, the friction forces in the secondary seal, and the inertia forces resulting from the non-negligible mass of the ring. For proper working conditions, the ring of the annular seal must be able to follow the vibration of the rotor without any damage. Under the effect of the unsteady hydrodynamic pressure field (engendered by the vibration of the rotor), of the friction force, and of the inertia force, the ring will describe a periodic, a quasi-periodic, or a chaotic motion. Damage can come from heating due to friction in the secondary seal or from repeated impacts between the rotor and the ring. The present work presents an analytic model able to take into account only the synchronous periodic whirl motion of the floating ring. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...] [article] Analytic modeling of floating ring annular seals [texte imprimé] / Arghir, Mihai, Auteur ; Manh-Hung Nguyen, Auteur ; David Tonon, Auteur . - 2012 . - 09 p.
Génie mécanique
Langues : Anglais (eng)
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 09 p.
Mots-clés : Chaos Friction Hydrodynamics Impact (mechanical) Rings (structures) Rotors Seals (stoppers) Stators Vibrations Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : In order to avoid contact between the vibrating rotor and the stator, annular seals are designed with a relatively large radial clearance (~100 µm) and, therefore, have an important leakage. The floating ring annular seal is able to reduce the leakage flow rate by using a much lower clearance. The seal is designed as a ring floating on the rotor in order to accommodate its vibrations. The pressure difference between the upstream and the downstream chambers is pressing the nose of the floating ring (secondary seal) against the stator. The forces acting on the floating ring are the resultant of the hydrodynamic pressure field inside the primary seal, the friction forces in the secondary seal, and the inertia forces resulting from the non-negligible mass of the ring. For proper working conditions, the ring of the annular seal must be able to follow the vibration of the rotor without any damage. Under the effect of the unsteady hydrodynamic pressure field (engendered by the vibration of the rotor), of the friction force, and of the inertia force, the ring will describe a periodic, a quasi-periodic, or a chaotic motion. Damage can come from heating due to friction in the secondary seal or from repeated impacts between the rotor and the ring. The present work presents an analytic model able to take into account only the synchronous periodic whirl motion of the floating ring. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...]
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 06 p.
Titre : Coupled thermomechanical fatigue tests for simulating load conditions in cooled turbine parts Type de document : texte imprimé Auteurs : Roland Mücke, Auteur ; Klaus Rau, Auteur Année de publication : 2012 Article en page(s) : 06 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Fatigue testing Gas turbines Lead Nickel alloys Stress relaxation Superalloys Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Modern heavy-duty gas turbines operate under hot gas temperatures that are much higher than the temperature capability of nickel superalloys. For that reason, advanced cooling technology is applied for reducing the metal temperature to an acceptable level. Highly cooled components, however, are characterized by large thermal gradients resulting in inhomogeneous temperature fields and complex thermomechanical load conditions. In particular, the different rates of stress relaxation due to the different metal temperatures on hot gas and cooling air exposed surfaces lead to load redistributions in cooled structures, which have to be considered in the lifetime prediction methodology. In this context, the paper describes coupled thermomechanical fatigue (CTMF) tests for simultaneously simulating load conditions on hot and cold surfaces of cooled turbine parts (Beck et al., 2001, “Experimental Analysis of the Interaction of Hot and Cold Volume Elements During Thermal Fatigue of Cooled Components Made From AISI 316 L Steel,” Z. Metallkunde, 92, pp. 875–881 and Rau et al., 2003, “Isothermal Thermo-mechanical and Complex Thermo-mechanical Fatigue Tests on AISI 316 L Steel—A Critical Evaluation,” Mater. Sci. Eng., A345, pp. 309–318). In contrary to standard thermomechanical fatigue (TMF) testing methods, CTMF tests involve the interaction between hot and cold regions of the parts and thus more closely simulates the material behavior in cooled gas turbine structures. The paper describes the methodology of CTMF tests and their application to typical load conditions in cooled gas turbine parts. Experimental results are compared with numerical predictions showing the advantages of the proposed testing method. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...] [article] Coupled thermomechanical fatigue tests for simulating load conditions in cooled turbine parts [texte imprimé] / Roland Mücke, Auteur ; Klaus Rau, Auteur . - 2012 . - 06 p.
Génie mécanique
Langues : Anglais (eng)
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 06 p.
Mots-clés : Fatigue testing Gas turbines Lead Nickel alloys Stress relaxation Superalloys Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Modern heavy-duty gas turbines operate under hot gas temperatures that are much higher than the temperature capability of nickel superalloys. For that reason, advanced cooling technology is applied for reducing the metal temperature to an acceptable level. Highly cooled components, however, are characterized by large thermal gradients resulting in inhomogeneous temperature fields and complex thermomechanical load conditions. In particular, the different rates of stress relaxation due to the different metal temperatures on hot gas and cooling air exposed surfaces lead to load redistributions in cooled structures, which have to be considered in the lifetime prediction methodology. In this context, the paper describes coupled thermomechanical fatigue (CTMF) tests for simultaneously simulating load conditions on hot and cold surfaces of cooled turbine parts (Beck et al., 2001, “Experimental Analysis of the Interaction of Hot and Cold Volume Elements During Thermal Fatigue of Cooled Components Made From AISI 316 L Steel,” Z. Metallkunde, 92, pp. 875–881 and Rau et al., 2003, “Isothermal Thermo-mechanical and Complex Thermo-mechanical Fatigue Tests on AISI 316 L Steel—A Critical Evaluation,” Mater. Sci. Eng., A345, pp. 309–318). In contrary to standard thermomechanical fatigue (TMF) testing methods, CTMF tests involve the interaction between hot and cold regions of the parts and thus more closely simulates the material behavior in cooled gas turbine structures. The paper describes the methodology of CTMF tests and their application to typical load conditions in cooled gas turbine parts. Experimental results are compared with numerical predictions showing the advantages of the proposed testing method. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...]
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 10 p.
Titre : A novel bulk-flow model for improved predictions of force coefficients in grooved oil seals operating eccentrically Type de document : texte imprimé Auteurs : Luis San Andrés, Auteur ; Adolfo Delgado, Auteur Année de publication : 2012 Article en page(s) : 10 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Compressors Finite element analysis Hydrodynamics Lubricating oils Machine bearings Rotors Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Oil seals in centrifugal compressors reduce leakage of the process gas into the support bearings and ambient. Under certain operating conditions of speed and pressure, oil seals lock, becoming a source of hydrodynamic instability due to excessively large cross coupled stiffness coefficients. It is a common practice to machine circumferential grooves, breaking the seal land, to isolate shear flow induced film pressures in contiguous lands, and hence reducing the seal cross coupled stiffnesses. Published tests results for oil seal rings shows that an inner land groove, shallow or deep, does not actually reduce the cross-stiffnesses as much as conventional models predict. In addition, the tested grooved oil seals evidenced large added mass coefficients while predictive models, based on classical lubrication theory, neglect fluid inertia effects. This paper introduces a bulk-flow model for groove oil seals operating eccentrically and its solution via the finite element (FE) method. The analysis relies on an effective groove depth, different from the physical depth, which delimits the upper boundary for the squeeze film flow. Predictions of rotordynamic force coefficients are compared to published experimental force coefficients for a smooth land seal and a seal with a single inner groove with depth equaling 15 times the land clearance. The test data represent operation at 10 krpm and 70 bar supply pressure, and four journal eccentricity ratios (e/c= 0, 0.3, 0.5, 0.7). Predictions from the current model agree with the test data for operation at the lowest eccentricities (e/c= 0.3) with discrepancies increasing at larger journal eccentricities. The new flow model is a significant improvement towards the accurate estimation of grooved seal cross-coupled stiffnesses and added mass coefficients; the latter was previously ignored or largely under predicted. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...] [article] A novel bulk-flow model for improved predictions of force coefficients in grooved oil seals operating eccentrically [texte imprimé] / Luis San Andrés, Auteur ; Adolfo Delgado, Auteur . - 2012 . - 10 p.
Génie mécanique
Langues : Anglais (eng)
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 10 p.
Mots-clés : Compressors Finite element analysis Hydrodynamics Lubricating oils Machine bearings Rotors Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Oil seals in centrifugal compressors reduce leakage of the process gas into the support bearings and ambient. Under certain operating conditions of speed and pressure, oil seals lock, becoming a source of hydrodynamic instability due to excessively large cross coupled stiffness coefficients. It is a common practice to machine circumferential grooves, breaking the seal land, to isolate shear flow induced film pressures in contiguous lands, and hence reducing the seal cross coupled stiffnesses. Published tests results for oil seal rings shows that an inner land groove, shallow or deep, does not actually reduce the cross-stiffnesses as much as conventional models predict. In addition, the tested grooved oil seals evidenced large added mass coefficients while predictive models, based on classical lubrication theory, neglect fluid inertia effects. This paper introduces a bulk-flow model for groove oil seals operating eccentrically and its solution via the finite element (FE) method. The analysis relies on an effective groove depth, different from the physical depth, which delimits the upper boundary for the squeeze film flow. Predictions of rotordynamic force coefficients are compared to published experimental force coefficients for a smooth land seal and a seal with a single inner groove with depth equaling 15 times the land clearance. The test data represent operation at 10 krpm and 70 bar supply pressure, and four journal eccentricity ratios (e/c= 0, 0.3, 0.5, 0.7). Predictions from the current model agree with the test data for operation at the lowest eccentricities (e/c= 0.3) with discrepancies increasing at larger journal eccentricities. The new flow model is a significant improvement towards the accurate estimation of grooved seal cross-coupled stiffnesses and added mass coefficients; the latter was previously ignored or largely under predicted. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...]
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 09 p.
Titre : Fuel property effects on PCCI combustion in a heavy-duty diesel engine Type de document : texte imprimé Auteurs : Cosmin E. Dumitrescu, Auteur ; W. Stuart Neill, Auteur ; Hongsheng Guo, Auteur Année de publication : 2012 Article en page(s) : 09 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Air pollution control Brakes Combustion Diesel engines Distillation Engine cylinders Fuel systems Ignition Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : An experimental study was performed to investigate fuel property effects on premixed charge compression ignition (PCCI) combustion in a heavy-duty diesel engine. A matrix of research diesel fuels designed by the Coordinating Research Council, referred to as the Fuels for Advanced Combustion Engines (FACE), was used. The fuel matrix design covers a wide range of cetane numbers (30 to 55), 90% distillation temperatures (270 to 340 °C) and aromatics content (20 to 45%). The fuels were tested in a single-cylinder Caterpillar diesel engine equipped with a common-rail fuel injection system. The engine was operated at 900 rpm, a relative air/fuel ratio of 1.2 and 60% exhaust gas recirculation (EGR) for all fuels. The study was limited to a single fuel injection event starting between −30° and 0 °CA after top dead center (aTDC) with a rail pressure of 150 MPa. The brake mean effective pressure (BMEP) ranged from 2.6 to 3.1 bar depending on the fuel and its injection timing. The experimental results show that cetane number was the most important fuel property affecting PCCI combustion behavior. The low cetane number fuels had better brake specific fuel consumption (BSFC) due to more optimized combustion phasing and shorter combustion duration. They also had a longer ignition delay period available for premixing, which led to near-zero soot emissions. The two fuels with high cetane number and high 90% distillation temperature produced significant soot emissions. The two fuels with high cetane number and high aromatics produced the highest brake specific NOx emissions, although the absolute values were below 0.1 g/kW-h. Brake specific HC and CO emissions were primarily a function of the combustion phasing, but the low cetane number fuels had slightly higher HC and lower CO emissions than the high cetane number fuels. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...] [article] Fuel property effects on PCCI combustion in a heavy-duty diesel engine [texte imprimé] / Cosmin E. Dumitrescu, Auteur ; W. Stuart Neill, Auteur ; Hongsheng Guo, Auteur . - 2012 . - 09 p.
Génie mécanique
Langues : Anglais (eng)
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 09 p.
Mots-clés : Air pollution control Brakes Combustion Diesel engines Distillation Engine cylinders Fuel systems Ignition Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : An experimental study was performed to investigate fuel property effects on premixed charge compression ignition (PCCI) combustion in a heavy-duty diesel engine. A matrix of research diesel fuels designed by the Coordinating Research Council, referred to as the Fuels for Advanced Combustion Engines (FACE), was used. The fuel matrix design covers a wide range of cetane numbers (30 to 55), 90% distillation temperatures (270 to 340 °C) and aromatics content (20 to 45%). The fuels were tested in a single-cylinder Caterpillar diesel engine equipped with a common-rail fuel injection system. The engine was operated at 900 rpm, a relative air/fuel ratio of 1.2 and 60% exhaust gas recirculation (EGR) for all fuels. The study was limited to a single fuel injection event starting between −30° and 0 °CA after top dead center (aTDC) with a rail pressure of 150 MPa. The brake mean effective pressure (BMEP) ranged from 2.6 to 3.1 bar depending on the fuel and its injection timing. The experimental results show that cetane number was the most important fuel property affecting PCCI combustion behavior. The low cetane number fuels had better brake specific fuel consumption (BSFC) due to more optimized combustion phasing and shorter combustion duration. They also had a longer ignition delay period available for premixing, which led to near-zero soot emissions. The two fuels with high cetane number and high 90% distillation temperature produced significant soot emissions. The two fuels with high cetane number and high aromatics produced the highest brake specific NOx emissions, although the absolute values were below 0.1 g/kW-h. Brake specific HC and CO emissions were primarily a function of the combustion phasing, but the low cetane number fuels had slightly higher HC and lower CO emissions than the high cetane number fuels. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...]
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 09 p.
Titre : Detection of combustion resonance using an ion current sensor in diesel engines Type de document : texte imprimé Auteurs : Tamer Badawy, Auteur ; Amit Shrestha, Auteur ; Naeim Henein, Auteur Année de publication : 2012 Article en page(s) : 09 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Diesel engines Pressure transducers Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : This paper discusses the use of an ion current sensor to detect combustion resonance in a heavy duty direct injection diesel engine. A modified glow plug is used to measure the ion current in addition to its main function in warming up the combustion chamber. A comparison is made between the combustion resonance determined from the signals of an ion current sensor, a cylinder pressure transducer, and an engine vibration sensor. Experiments are conducted on a four cylinder, turbocharged 4.5 liter diesel engine to determine the potential of using the ion current sensor to detect combustion resonance under different injection pressures and exhaust gas recirculation rates. It is concluded that the ion current signal can be used to determine the timing, amplitude, frequency, and duration of the resonance. The sensor output has the potential to be used as a feedback signal to the ECU (electronic control unit) to minimize engine vibration and noise. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...] [article] Detection of combustion resonance using an ion current sensor in diesel engines [texte imprimé] / Tamer Badawy, Auteur ; Amit Shrestha, Auteur ; Naeim Henein, Auteur . - 2012 . - 09 p.
Génie mécanique
Langues : Anglais (eng)
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 09 p.
Mots-clés : Diesel engines Pressure transducers Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : This paper discusses the use of an ion current sensor to detect combustion resonance in a heavy duty direct injection diesel engine. A modified glow plug is used to measure the ion current in addition to its main function in warming up the combustion chamber. A comparison is made between the combustion resonance determined from the signals of an ion current sensor, a cylinder pressure transducer, and an engine vibration sensor. Experiments are conducted on a four cylinder, turbocharged 4.5 liter diesel engine to determine the potential of using the ion current sensor to detect combustion resonance under different injection pressures and exhaust gas recirculation rates. It is concluded that the ion current signal can be used to determine the timing, amplitude, frequency, and duration of the resonance. The sensor output has the potential to be used as a feedback signal to the ECU (electronic control unit) to minimize engine vibration and noise. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...]
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 04 p.
Titre : Real-time execution of a high fidelity aero-thermodynamic turbofan engine simulation Type de document : texte imprimé Auteurs : Igor Fuksman, Auteur ; Steven Sirica, Auteur Année de publication : 2012 Article en page(s) : 04 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Aerodynamics Flow simulation Gas turbines Jet engines Reduced order systems Thermodynamics Transfer functions Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : In the past, a typical way of executing simulations in a real-time environment had been to use transfer function models, state-variable models, or reduced-order aero-thermodynamic models. These models are typically not as accurate as the conventional full-fidelity aero-thermodynamic simulations used as a basis for the generation of real-time models. Also, there is a cost associated with the creation and maintenance of these derived real-time models. The ultimate goal is to use the high fidelity aero-thermodynamic simulation as the real-time model. However, execution of the high fidelity aero-thermodynamic simulation in a real-time environment is a challenging objective since accuracy of the simulation cannot be sacrificed to optimize execution speed, yet execution speed still has to be limited by some means to fit into real-time constraint. This paper discusses the methodology used to resolve this challenge, thereby enabling use of a contemporary turbofan engine high fidelity aero-thermodynamic simulation in real-time environments. This publication reflects the work that was initially presented at the ASME Turbo Expo 2011 (Fuksman and Sirica, 2011, “Real-Time Execution of a High Fidelity Aero-Thermodynamic Turbofan Engine Simulation,” ASME Turbo Expo, Jun. 6-10, Vancouver, Canada, Paper No. GT2011-46661). DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...] [article] Real-time execution of a high fidelity aero-thermodynamic turbofan engine simulation [texte imprimé] / Igor Fuksman, Auteur ; Steven Sirica, Auteur . - 2012 . - 04 p.
Génie mécanique
Langues : Anglais (eng)
in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 5 (Mai 2012) . - 04 p.
Mots-clés : Aerodynamics Flow simulation Gas turbines Jet engines Reduced order systems Thermodynamics Transfer functions Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : In the past, a typical way of executing simulations in a real-time environment had been to use transfer function models, state-variable models, or reduced-order aero-thermodynamic models. These models are typically not as accurate as the conventional full-fidelity aero-thermodynamic simulations used as a basis for the generation of real-time models. Also, there is a cost associated with the creation and maintenance of these derived real-time models. The ultimate goal is to use the high fidelity aero-thermodynamic simulation as the real-time model. However, execution of the high fidelity aero-thermodynamic simulation in a real-time environment is a challenging objective since accuracy of the simulation cannot be sacrificed to optimize execution speed, yet execution speed still has to be limited by some means to fit into real-time constraint. This paper discusses the methodology used to resolve this challenge, thereby enabling use of a contemporary turbofan engine high fidelity aero-thermodynamic simulation in real-time environments. This publication reflects the work that was initially presented at the ASME Turbo Expo 2011 (Fuksman and Sirica, 2011, “Real-Time Execution of a High Fidelity Aero-Thermodynamic Turbofan Engine Simulation,” ASME Turbo Expo, Jun. 6-10, Vancouver, Canada, Paper No. GT2011-46661). DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000005 [...]
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