Dépouillements

Far-field noise control in supersonic jets from conical and contoured nozzles / Kim, Jin-Hwa in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 133 N° 8 (Août 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 09 p. Titre : Far-field noise control in supersonic jets from conical and contoured nozzles Type de document : texte imprimé Auteurs : Kim, Jin-Hwa, Auteur ; Kearney-Fischer, Martin, Auteur ; Mo, Samimy, Auteur Année de publication : 2011 Article en page(s) : 09 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Acoustic  noise  Jets  Mach  number  Microphone  arrays  Nozzles  Supersonic  flow Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Plasma actuators are used to control far-field noise in Mach 1.65 jets from contoured and conical supersonic axisymmetric nozzles (henceforth, contoured and conical jets, respectively). The contoured nozzle is designed using the method of characteristics for a shock-free jet. The conical nozzle has converging and diverging conical sections with a sharp throat. Eight plasma actuators, distributed uniformly around the nozzle exit, are used and the jet is forced with azimuthal modes (m) 0–3 and ±4 and forcing Strouhal numbers ranging from 0.09 to 4.0. The far-field acoustic noise is measured by a linear microphone array covering polar angles from 25 deg to 80 deg relative to the jet axis. In both jets, the lower forcing azimuthal modes (m=0 and 1) are less effective than the higher modes (m=2, 3, and ±4), which have similar levels of overall sound pressure level (OASPL) reduction. At shallow angles relative to the jet axis, the reduction in OASPL is about 1.6–1.8 dB at low forcing Strouhal numbers in both jets at the most effective forcing mode of m=3. However, the OASPL in the sideline direction is only slightly increased (about 1 dB) for both the contoured and conical jets at m=3. The reduction at shallow polar angles is related to the decrease in the peak mixing noise level in both jets. The range of forcing Strouhal numbers providing significant noise reduction and the range of polar angles over which the noise is reduced are both much larger in the conical jet compared with the contoured jet. The screech tones are also reduced or suppressed – most likely due to weakening of naturally occurring structures by forcing. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...] [article] Far-field noise control in supersonic jets from conical and contoured nozzles [texte imprimé] / Kim, Jin-Hwa, Auteur ; Kearney-Fischer, Martin, Auteur ; Mo, Samimy, Auteur . - 2011 . - 09 p. Génie Mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 09 p. Mots-clés : Acoustic  noise  Jets  Mach  number  Microphone  arrays  Nozzles  Supersonic  flow Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Plasma actuators are used to control far-field noise in Mach 1.65 jets from contoured and conical supersonic axisymmetric nozzles (henceforth, contoured and conical jets, respectively). The contoured nozzle is designed using the method of characteristics for a shock-free jet. The conical nozzle has converging and diverging conical sections with a sharp throat. Eight plasma actuators, distributed uniformly around the nozzle exit, are used and the jet is forced with azimuthal modes (m) 0–3 and ±4 and forcing Strouhal numbers ranging from 0.09 to 4.0. The far-field acoustic noise is measured by a linear microphone array covering polar angles from 25 deg to 80 deg relative to the jet axis. In both jets, the lower forcing azimuthal modes (m=0 and 1) are less effective than the higher modes (m=2, 3, and ±4), which have similar levels of overall sound pressure level (OASPL) reduction. At shallow angles relative to the jet axis, the reduction in OASPL is about 1.6–1.8 dB at low forcing Strouhal numbers in both jets at the most effective forcing mode of m=3. However, the OASPL in the sideline direction is only slightly increased (about 1 dB) for both the contoured and conical jets at m=3. The reduction at shallow polar angles is related to the decrease in the peak mixing noise level in both jets. The range of forcing Strouhal numbers providing significant noise reduction and the range of polar angles over which the noise is reduced are both much larger in the conical jet compared with the contoured jet. The screech tones are also reduced or suppressed – most likely due to weakening of naturally occurring structures by forcing. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...]

Seven-sensor fast-response probe for full-scale wind turbine flowfield measurements / Mansour, M. in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 133 N° 8 (Août 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 08 p. Titre : Seven-sensor fast-response probe for full-scale wind turbine flowfield measurements Type de document : texte imprimé Auteurs : Mansour, M., Auteur ; Kocer, G., Auteur ; Lenherr, C., Auteur Année de publication : 2011 Article en page(s) : 08 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Aerodynamics  Blades  Remotely  operated  vehicles  Wind  turbines Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The unsteady wind profile in the atmospheric boundary layer upstream of a modern wind turbine is measured. The measurements are accomplished using a novel measurement approach that is comprised of an autonomous uninhabited aerial vehicle (UAV) that is equipped with a seven-sensor fast-response aerodynamic probe (F7S-UAV). The autonomous UAV enables high spatial resolution (~6.3% of rotor diameter) measurements, which hitherto have not been accomplished around full-scale wind turbines. The F7S-UAV probe developed at ETH Zurich is the key-enabling technology for the measurements. The time-averaged wind profile from the F7S-UAV probe is found to be in very good agreement to an independently measured profile using the UAV. This time-averaged profile, which is measured in moderately complex terrain, differs by as much as 30% from the wind profile that is extrapolated from a logarithmic height formula; therefore, the limited utility of extrapolated profiles, which are commonly used in site assessments, is made evident. The time-varying wind profiles show that at a given height, the velocity fluctuations can be as much as 44% of the time-averaged velocity, therefore indicating that there are substantial loads that may impact the fatigue life of the wind turbine's components. Furthermore, the shear in the velocity profile also subjects the fixed pitch blade to varying incidences and loading. Analysis of the associated velocity triangles indicates that the sectional lift coefficient at midspan of this modern turbine would vary by 12% in the measured time-averaged wind profile. These variations must be accounted in the structural design of the blades. Thus, the measurements of the unsteady wind profile accomplished with this novel measurement system demonstrate that it is a cost effective complement to the suite of available site assessment measurement tools. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...] [article] Seven-sensor fast-response probe for full-scale wind turbine flowfield measurements [texte imprimé] / Mansour, M., Auteur ; Kocer, G., Auteur ; Lenherr, C., Auteur . - 2011 . - 08 p. Génie Mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 08 p. Mots-clés : Aerodynamics  Blades  Remotely  operated  vehicles  Wind  turbines Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The unsteady wind profile in the atmospheric boundary layer upstream of a modern wind turbine is measured. The measurements are accomplished using a novel measurement approach that is comprised of an autonomous uninhabited aerial vehicle (UAV) that is equipped with a seven-sensor fast-response aerodynamic probe (F7S-UAV). The autonomous UAV enables high spatial resolution (~6.3% of rotor diameter) measurements, which hitherto have not been accomplished around full-scale wind turbines. The F7S-UAV probe developed at ETH Zurich is the key-enabling technology for the measurements. The time-averaged wind profile from the F7S-UAV probe is found to be in very good agreement to an independently measured profile using the UAV. This time-averaged profile, which is measured in moderately complex terrain, differs by as much as 30% from the wind profile that is extrapolated from a logarithmic height formula; therefore, the limited utility of extrapolated profiles, which are commonly used in site assessments, is made evident. The time-varying wind profiles show that at a given height, the velocity fluctuations can be as much as 44% of the time-averaged velocity, therefore indicating that there are substantial loads that may impact the fatigue life of the wind turbine's components. Furthermore, the shear in the velocity profile also subjects the fixed pitch blade to varying incidences and loading. Analysis of the associated velocity triangles indicates that the sectional lift coefficient at midspan of this modern turbine would vary by 12% in the measured time-averaged wind profile. These variations must be accounted in the structural design of the blades. Thus, the measurements of the unsteady wind profile accomplished with this novel measurement system demonstrate that it is a cost effective complement to the suite of available site assessment measurement tools. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...]

Data-driven fault detection in aircraft engines with noisy sensor measurements / Sarkar, Soumik in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 133 N° 8 (Août 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 10 p. Titre : Data-driven fault detection in aircraft engines with noisy sensor measurements Type de document : texte imprimé Auteurs : Sarkar, Soumik, Auteur ; Xin Jin, Auteur ; Ray, Asok, Auteur Année de publication : 2011 Article en page(s) : 10 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Aerospace  engines  Aerospace  simulation  Aircraft  testing  Fault  location  Feature  extraction  Gas  turbines  Pattern  classification  Sensors  Time  series Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : An inherent difficulty in sensor-data-driven fault detection is that the detection performance could be drastically reduced under sensor degradation (e.g., drift and noise). Complementary to traditional model-based techniques for fault detection, this paper proposes symbolic dynamic filtering by optimally partitioning the time series data of sensor observation. The objective here is to mask the effects of sensor noise level variation and magnify the system fault signatures. In this regard, the concepts of feature extraction and pattern classification are used for fault detection in aircraft gas turbine engines. The proposed methodology of data-driven fault detection is tested and validated on the Commercial Modular Aero-Propulsion System Simulation (C-MAPSS) test-bed developed by NASA for noisy (i.e., increased variance) sensor signals. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...] [article] Data-driven fault detection in aircraft engines with noisy sensor measurements [texte imprimé] / Sarkar, Soumik, Auteur ; Xin Jin, Auteur ; Ray, Asok, Auteur . - 2011 . - 10 p. Génie Mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 10 p. Mots-clés : Aerospace  engines  Aerospace  simulation  Aircraft  testing  Fault  location  Feature  extraction  Gas  turbines  Pattern  classification  Sensors  Time  series Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : An inherent difficulty in sensor-data-driven fault detection is that the detection performance could be drastically reduced under sensor degradation (e.g., drift and noise). Complementary to traditional model-based techniques for fault detection, this paper proposes symbolic dynamic filtering by optimally partitioning the time series data of sensor observation. The objective here is to mask the effects of sensor noise level variation and magnify the system fault signatures. In this regard, the concepts of feature extraction and pattern classification are used for fault detection in aircraft gas turbine engines. The proposed methodology of data-driven fault detection is tested and validated on the Commercial Modular Aero-Propulsion System Simulation (C-MAPSS) test-bed developed by NASA for noisy (i.e., increased variance) sensor signals. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...]

Unsteady pressure measurements with a fast response cooled probe in high temperature gas turbine environments / Mersinligil, Mehmet in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 133 N° 8 (Août 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 09 p. Titre : Unsteady pressure measurements with a fast response cooled probe in high temperature gas turbine environments Type de document : texte imprimé Auteurs : Mersinligil, Mehmet, Auteur ; Brouckaert, Jean-François, Auteur ; Desset, Julien, Auteur Année de publication : 2011 Article en page(s) : 09 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Combustion  Cooling  Gas  turbines  Jet  engines  Mach  number  Pressure  measurement  Pressure  sensors  Probes  Time  series Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : This paper presents the first experimental engine and test rig results obtained from a fast response cooled total pressure probe. The first objective of the probe design was to favor continuous immersion of the probe into the engine to obtain a time series of pressure with a high bandwidth and, therefore, statistically representative average fluctuations at the blade passing frequency. The probe is water cooled by a high pressure cooling system and uses a conventional piezoresistive pressure sensor, which yields, therefore, both time-averaged and time-resolved pressures. The initial design target was to gain the capability of performing measurements at the temperature conditions typically found at high pressure turbine exit (800–1100°C) with a bandwidth of at least 40 kHz and in the long term at combustor exit (2000 K or higher). The probe was first traversed at the turbine exit of a Rolls-Royce Viper turbojet engine at exhaust temperatures around 750°C and absolute pressure of 2.1 bars. The probe was able to resolve the high blade passing frequency ([approximate]23 kHz) and several harmonics of up to 100 kHz. Besides the average total pressure distributions rom the radial traverses, phase-locked averages and random unsteadiness are presented. The probe was also used in a virtual three-hole mode yielding unsteady yaw angle, static pressure, and Mach number. The same probe was used for measurements in a Rolls-Royce intermediate pressure burner rig. Traverses were performed inside the flame tube of a kerosene burner at temperatures above 1600°C. The probe successfully measured the total pressure distribution in the flame tube and typical frequencies of combustion instabilities were identified during rumble conditions. The cooling performance of the probe is compared with estimations at the design stage and found to be in good agreement. The frequency response of the probe is compared with cold shock-tube results and a significant increase in the natural frequency of the line-cavity system formed by the conduction cooled screen in front of the miniature pressure sensor were observed. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...] [article] Unsteady pressure measurements with a fast response cooled probe in high temperature gas turbine environments [texte imprimé] / Mersinligil, Mehmet, Auteur ; Brouckaert, Jean-François, Auteur ; Desset, Julien, Auteur . - 2011 . - 09 p. Génie Mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 09 p. Mots-clés : Combustion  Cooling  Gas  turbines  Jet  engines  Mach  number  Pressure  measurement  Pressure  sensors  Probes  Time  series Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : This paper presents the first experimental engine and test rig results obtained from a fast response cooled total pressure probe. The first objective of the probe design was to favor continuous immersion of the probe into the engine to obtain a time series of pressure with a high bandwidth and, therefore, statistically representative average fluctuations at the blade passing frequency. The probe is water cooled by a high pressure cooling system and uses a conventional piezoresistive pressure sensor, which yields, therefore, both time-averaged and time-resolved pressures. The initial design target was to gain the capability of performing measurements at the temperature conditions typically found at high pressure turbine exit (800–1100°C) with a bandwidth of at least 40 kHz and in the long term at combustor exit (2000 K or higher). The probe was first traversed at the turbine exit of a Rolls-Royce Viper turbojet engine at exhaust temperatures around 750°C and absolute pressure of 2.1 bars. The probe was able to resolve the high blade passing frequency ([approximate]23 kHz) and several harmonics of up to 100 kHz. Besides the average total pressure distributions rom the radial traverses, phase-locked averages and random unsteadiness are presented. The probe was also used in a virtual three-hole mode yielding unsteady yaw angle, static pressure, and Mach number. The same probe was used for measurements in a Rolls-Royce intermediate pressure burner rig. Traverses were performed inside the flame tube of a kerosene burner at temperatures above 1600°C. The probe successfully measured the total pressure distribution in the flame tube and typical frequencies of combustion instabilities were identified during rumble conditions. The cooling performance of the probe is compared with estimations at the design stage and found to be in good agreement. The frequency response of the probe is compared with cold shock-tube results and a significant increase in the natural frequency of the line-cavity system formed by the conduction cooled screen in front of the miniature pressure sensor were observed. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...]

A study on engine health monitoring in the frequency domain / Borguet, S. in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 133 N° 8 (Août 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 08 p. Titre : A study on engine health monitoring in the frequency domain Type de document : texte imprimé Auteurs : Borguet, S., Auteur ; Henriksson, M., Auteur ; McKelvey, T., Auteur Année de publication : 2011 Article en page(s) : 08 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Gas  path  analysis  Frequency  domain  Least-squares  System  identification Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Most of the techniques developed to date for module performance analysis rely on steady-state measurements from a single operating point to evaluate the level of deterioration of an engine. One of the major difficulties associated with this estimation problem comes from its underdetermined nature. It results from the fact that the number of health parameters exceeds the number of available sensors. Among the panel of remedies to this issue, a few authors have investigated the potential of using data collected during a transient operation of the engine. A major outcome of these studies is an improvement in the assessed health condition. The present study proposes a framework that formalizes this observation for a given class of input signals. The analysis is performed in the frequency domain, following the lines of system identification theory. More specifically, the mean-squared estimation error is shown to drastically decrease when using transient input signals. This study is conducted with an engine model representative of a commercial turbofan. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...] [article] A study on engine health monitoring in the frequency domain [texte imprimé] / Borguet, S., Auteur ; Henriksson, M., Auteur ; McKelvey, T., Auteur . - 2011 . - 08 p. Génie Mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 08 p. Mots-clés : Gas  path  analysis  Frequency  domain  Least-squares  System  identification Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Most of the techniques developed to date for module performance analysis rely on steady-state measurements from a single operating point to evaluate the level of deterioration of an engine. One of the major difficulties associated with this estimation problem comes from its underdetermined nature. It results from the fact that the number of health parameters exceeds the number of available sensors. Among the panel of remedies to this issue, a few authors have investigated the potential of using data collected during a transient operation of the engine. A major outcome of these studies is an improvement in the assessed health condition. The present study proposes a framework that formalizes this observation for a given class of input signals. The analysis is performed in the frequency domain, following the lines of system identification theory. More specifically, the mean-squared estimation error is shown to drastically decrease when using transient input signals. This study is conducted with an engine model representative of a commercial turbofan. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...]

Wet compression analysis including velocity slip effects / White, A. J. in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 133 N° 8 (Août 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 08 p. Titre : Wet compression analysis including velocity slip effects Type de document : texte imprimé Auteurs : White, A. J., Auteur ; Meacock, A. J., Auteur Année de publication : 2011 Article en page(s) : 08 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Compressors  Cooling  Drops  Evaporation  Gas  turbines  Heat  transfer  Mass  transfer Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Injection of water droplets into industrial gas turbines in order to boost power output is now common practice. The intention is usually to saturate and cool the intake air, especially in hot and dry climates, but in many cases, droplets carry over into the compressor and continue to evaporate. Evaporation within the compressor itself (often referred to as overspray) is also central to several advanced wet cycles, including the moist air turbine and the so-called TOP Humidified Air Turbine (TOPHAT) cycle. The resulting wet compression process affords a number of thermodynamic advantages, such as reduced compression work and increased mass flow rate and specific heat capacity of the turbine flow. Against these benefits, many of the compressor stages will operate at significantly off-design flow angles, thereby compromising aerodynamic performance. The calculations presented here entail coupling a mean-line compressor calculation method with droplet evaporation routines and a numerical method for estimating radial and circumferential slip velocities. The impingement of droplets onto blades and the various associated processes (including film evaporation) are also taken into account. The calculations allow for a polydispersion of droplet sizes and droplet temperature relaxation effects (i.e., the full droplet energy equation is solved rather than assuming that droplets adopt the wet-bulb temperature). The method is applied to a generic single-shaft 12-stage compressor. Results are presented for computed droplet trajectories, the overall effect on compressor characteristics (and how this depends on droplet size), and the effects of deposition and subsequent film evaporation. As with previously published wet compression calculations (with no velocity slip), it is found that pressure rise characteristics shift to higher mass flow and pressure ratio with increasing water injection rate and that aerodynamic efficiency falls due to the stages moving away from their design point. For droplet sizes typical of fog boosting, the overall effect of slip is to slightly increase the evaporative cooling effect through the enhanced heat and mass transfer rates. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...] [article] Wet compression analysis including velocity slip effects [texte imprimé] / White, A. J., Auteur ; Meacock, A. J., Auteur . - 2011 . - 08 p. Génie Mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 08 p. Mots-clés : Compressors  Cooling  Drops  Evaporation  Gas  turbines  Heat  transfer  Mass  transfer Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Injection of water droplets into industrial gas turbines in order to boost power output is now common practice. The intention is usually to saturate and cool the intake air, especially in hot and dry climates, but in many cases, droplets carry over into the compressor and continue to evaporate. Evaporation within the compressor itself (often referred to as overspray) is also central to several advanced wet cycles, including the moist air turbine and the so-called TOP Humidified Air Turbine (TOPHAT) cycle. The resulting wet compression process affords a number of thermodynamic advantages, such as reduced compression work and increased mass flow rate and specific heat capacity of the turbine flow. Against these benefits, many of the compressor stages will operate at significantly off-design flow angles, thereby compromising aerodynamic performance. The calculations presented here entail coupling a mean-line compressor calculation method with droplet evaporation routines and a numerical method for estimating radial and circumferential slip velocities. The impingement of droplets onto blades and the various associated processes (including film evaporation) are also taken into account. The calculations allow for a polydispersion of droplet sizes and droplet temperature relaxation effects (i.e., the full droplet energy equation is solved rather than assuming that droplets adopt the wet-bulb temperature). The method is applied to a generic single-shaft 12-stage compressor. Results are presented for computed droplet trajectories, the overall effect on compressor characteristics (and how this depends on droplet size), and the effects of deposition and subsequent film evaporation. As with previously published wet compression calculations (with no velocity slip), it is found that pressure rise characteristics shift to higher mass flow and pressure ratio with increasing water injection rate and that aerodynamic efficiency falls due to the stages moving away from their design point. For droplet sizes typical of fog boosting, the overall effect of slip is to slightly increase the evaporative cooling effect through the enhanced heat and mass transfer rates. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...]

A sub-idle compressor characteristic generation method with enhanced physical background / Zachos, Pavlos K. in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 133 N° 8 (Août 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 08 p. Titre : A sub-idle compressor characteristic generation method with enhanced physical background Type de document : texte imprimé Auteurs : Zachos, Pavlos K., Auteur ; Aslanidou, Ioanna, Auteur ; Pachidis, Vassilios, Auteur Année de publication : 2011 Article en page(s) : 08 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Compressors  Extrapolation  Gas  turbines  Rotors Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Sub-idle is a very challenging operating region as the performance of a gas turbine engine changes significantly compared with design conditions. In addition, the regulations for new and existing engines are becoming stricter and the prediction of engine relight capability is essential. In order to predict the performance of an engine, detailed component maps are required. The data obtained from rig tests are insufficient at low speeds, creating the need for generation of maps within the sub-idle regime. The first step toward this direction is the use of an extrapolation process. This is a purely mathematical process and the results are not usually of sufficient accuracy. In addition, this method does not provide any insight on the physical phenomena governing the operation of the compressor at low speeds. The accuracy of the resulting compressor map can be increased with a better low speed region definition; this can be achieved via the thorough study of a locked rotor compressor, enabling the derivation of the zero rotational speed line and allowing an interpolation process for the generation of the low speed part of the characteristic. In this work, an enhanced sub-idle compressor map generation technique is proposed. The suggested methodology enables the generation of characteristics at far off-design conditions with enhanced physical background. Alternative parameters for map representation are also introduced. Provided that the all the blade rows of the compressor are of known geometry, a numerical analysis is used for the calculation of the characteristic of the half stage and a stage stacking method is employed to create the entire compressor characteristic. This way, the sub-idle region of the map can be calculated through interpolation, which provides a more accurate and predictive technique. Application of the method for compressor map generation showed that the proposed interpolation approach is robust and capable of enhancing any performance simulation tool used for the prediction of transient altitude relight or ground-starting maneuvers. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...] [article] A sub-idle compressor characteristic generation method with enhanced physical background [texte imprimé] / Zachos, Pavlos K., Auteur ; Aslanidou, Ioanna, Auteur ; Pachidis, Vassilios, Auteur . - 2011 . - 08 p. Génie Mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 08 p. Mots-clés : Compressors  Extrapolation  Gas  turbines  Rotors Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Sub-idle is a very challenging operating region as the performance of a gas turbine engine changes significantly compared with design conditions. In addition, the regulations for new and existing engines are becoming stricter and the prediction of engine relight capability is essential. In order to predict the performance of an engine, detailed component maps are required. The data obtained from rig tests are insufficient at low speeds, creating the need for generation of maps within the sub-idle regime. The first step toward this direction is the use of an extrapolation process. This is a purely mathematical process and the results are not usually of sufficient accuracy. In addition, this method does not provide any insight on the physical phenomena governing the operation of the compressor at low speeds. The accuracy of the resulting compressor map can be increased with a better low speed region definition; this can be achieved via the thorough study of a locked rotor compressor, enabling the derivation of the zero rotational speed line and allowing an interpolation process for the generation of the low speed part of the characteristic. In this work, an enhanced sub-idle compressor map generation technique is proposed. The suggested methodology enables the generation of characteristics at far off-design conditions with enhanced physical background. Alternative parameters for map representation are also introduced. Provided that the all the blade rows of the compressor are of known geometry, a numerical analysis is used for the calculation of the characteristic of the half stage and a stage stacking method is employed to create the entire compressor characteristic. This way, the sub-idle region of the map can be calculated through interpolation, which provides a more accurate and predictive technique. Application of the method for compressor map generation showed that the proposed interpolation approach is robust and capable of enhancing any performance simulation tool used for the prediction of transient altitude relight or ground-starting maneuvers. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...]

On the behavior of water droplets when moving onto blade surface in a wet compression transonic compressor / Sun, Lanxin in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 133 N° 8 (Août 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 10 p. Titre : On the behavior of water droplets when moving onto blade surface in a wet compression transonic compressor Type de document : texte imprimé Auteurs : Sun, Lanxin, Auteur ; Zheng, Qun, Auteur ; Luo, Mingcong, Auteur Année de publication : 2011 Article en page(s) : 10 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Blades  Compressors  Drops  Rotors,  sprays  Two-phase  flow Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The process of wet compression in an axial compressor is an intricate two-phase flow involving not only heat and mass transfer processes but also droplet breakup and even formation of discontinuous water film on the blade surface and then breaking into droplets. In this paper, the droplet-wall interactions are analyzed using the theory of spray wall impingement through two computational models for an isolated transonic compressor rotor (NASA rotor 37). Model 1, representing spread phenomenon, assumes that all droplets impacting on the blade are trapped in the water film and subsequently released from its trailing edge and enter the wake region with an equivalent mass flow but bigger in diameter and smaller in number. Whereas, the model 2, representing splashing phenomenon, assumes that upon impacting on the blade, the droplets will breakup into many smaller ones. The three-dimensional flow simulation results of these two models are analyzed and compared in this paper. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...] [article] On the behavior of water droplets when moving onto blade surface in a wet compression transonic compressor [texte imprimé] / Sun, Lanxin, Auteur ; Zheng, Qun, Auteur ; Luo, Mingcong, Auteur . - 2011 . - 10 p. Génie Mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 10 p. Mots-clés : Blades  Compressors  Drops  Rotors,  sprays  Two-phase  flow Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The process of wet compression in an axial compressor is an intricate two-phase flow involving not only heat and mass transfer processes but also droplet breakup and even formation of discontinuous water film on the blade surface and then breaking into droplets. In this paper, the droplet-wall interactions are analyzed using the theory of spray wall impingement through two computational models for an isolated transonic compressor rotor (NASA rotor 37). Model 1, representing spread phenomenon, assumes that all droplets impacting on the blade are trapped in the water film and subsequently released from its trailing edge and enter the wake region with an equivalent mass flow but bigger in diameter and smaller in number. Whereas, the model 2, representing splashing phenomenon, assumes that upon impacting on the blade, the droplets will breakup into many smaller ones. The three-dimensional flow simulation results of these two models are analyzed and compared in this paper. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...]

Investigation of stress assisted grain boundary oxidation cracking in MAR-M002 high pressure turbine blades / Selvig, Austin in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 133 N° 8 (Août 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 08 p. Titre : Investigation of stress assisted grain boundary oxidation cracking in MAR-M002 high pressure turbine blades Type de document : texte imprimé Auteurs : Selvig, Austin, Auteur ; Huang, Xiao, Auteur ; Hildebrand, Mike, Auteur Année de publication : 2011 Article en page(s) : 08 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Alumina  Blades  Cracks  Diffusion  Engines  Gas  turbines  Grain  boundaries  Hafnium  compounds  Oxidation  Scanning  electron  microscopy  X-ray  chemical  analysis Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Modern superalloys have enabled high pressure turbine (HPT) blades in gas turbine engines (GTE) to operate at higher temperatures. Unfortunately, the complexity of these materials can make it difficult to understand the failure mechanisms of these blades. HPT blades made of the nickel-based superalloy Mar-M002 have been found to suffer from stress assisted grain boundary oxidation (SAGBO) cracking. HPT blades removed from an RB211-24C aeroderivative industrial GTE were sectioned, and the cracks and microstructure were studied using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). No cracks were found on the external surface of the blade, which had been coated with an oxidation resistant material. Surface irregularities were found along the walls of the inner cooling channels throughout the entire blade. Larger SAGBO cracks were observed to be near the lower 25% span of the blade and had initiated from the surfaces of the cooling channels. SEM/EDS analyses showed that these cracks had large amounts of alumina and hafnium-rich particles within them. It is evident that these cracks occurred in locations where the combination of high stress and high temperature led to higher rates of oxygen diffusion and subsequent oxidation of grain boundary carbides. Hafnium carbide precipitates along the grain boundaries expanded as they converted into hafnium oxide, thus further increasing the stress. It is envisaged that this increase in stress along the grain boundary has caused the cracks to initiate and coalesce. Based on this observation, it is believed that the inner cooling channels of these HPT blades could benefit from the application of an oxidation resistant coating in order to prevent or delay the formation of these cracks. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...] [article] Investigation of stress assisted grain boundary oxidation cracking in MAR-M002 high pressure turbine blades [texte imprimé] / Selvig, Austin, Auteur ; Huang, Xiao, Auteur ; Hildebrand, Mike, Auteur . - 2011 . - 08 p. Génie Mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 08 p. Mots-clés : Alumina  Blades  Cracks  Diffusion  Engines  Gas  turbines  Grain  boundaries  Hafnium  compounds  Oxidation  Scanning  electron  microscopy  X-ray  chemical  analysis Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Modern superalloys have enabled high pressure turbine (HPT) blades in gas turbine engines (GTE) to operate at higher temperatures. Unfortunately, the complexity of these materials can make it difficult to understand the failure mechanisms of these blades. HPT blades made of the nickel-based superalloy Mar-M002 have been found to suffer from stress assisted grain boundary oxidation (SAGBO) cracking. HPT blades removed from an RB211-24C aeroderivative industrial GTE were sectioned, and the cracks and microstructure were studied using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). No cracks were found on the external surface of the blade, which had been coated with an oxidation resistant material. Surface irregularities were found along the walls of the inner cooling channels throughout the entire blade. Larger SAGBO cracks were observed to be near the lower 25% span of the blade and had initiated from the surfaces of the cooling channels. SEM/EDS analyses showed that these cracks had large amounts of alumina and hafnium-rich particles within them. It is evident that these cracks occurred in locations where the combination of high stress and high temperature led to higher rates of oxygen diffusion and subsequent oxidation of grain boundary carbides. Hafnium carbide precipitates along the grain boundaries expanded as they converted into hafnium oxide, thus further increasing the stress. It is envisaged that this increase in stress along the grain boundary has caused the cracks to initiate and coalesce. Based on this observation, it is believed that the inner cooling channels of these HPT blades could benefit from the application of an oxidation resistant coating in order to prevent or delay the formation of these cracks. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...]

Design and testing of a micromix combustor with recuperative wall cooling for a hydrogen fueled µ-scale gas turbine / Robinson, A. E. in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 133 N° 8 (Août 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 08 p. Titre : Design and testing of a micromix combustor with recuperative wall cooling for a hydrogen fueled µ-scale gas turbine Type de document : texte imprimé Auteurs : Robinson, A. E., Auteur ; Funke, H. H.-W., Auteur ; Hendrick, P., Auteur Année de publication : 2011 Article en page(s) : 08 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Gas  turbines  Remotely  operated  vehicles  Turbomachinery Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : For more than 1 decade up to now, there is an ongoing interest in small gas turbines downsized to microscale. With their high energy density, they offer a great potential as a substitute for today's unwieldy accumulators found in a variety of applications such as laptops, small tools, etc. But microscale gas turbines could not only be used for generating electricity, they could also produce thrust for powering small unmanned aerial vehicles or similar devices. Beneath all the great design challenges with the rotating parts of the turbomachinery at this small scale, another crucial item is in fact the combustion chamber needed for a safe and reliable operation. With the so-called regular micromix burning principle for hydrogen successfully downscaled in an initial combustion chamber prototype of 10 kW energy output, this paper describes a new design attempt aimed at the integration possibilities in a µ-scale gas turbine. For manufacturing the combustion chamber completely out of stainless steel components, a recuperative wall cooling was introduced to keep the temperatures in an acceptable range. Also a new way of an integrated ignition was developed. The detailed description of the prototype's design is followed by an in depth report about the test results. The experimental investigations comprise a set of mass flow variations, coupled with a variation of the equivalence ratio for each mass flow at different inlet temperatures and pressures. With the data obtained by an exhaust gas analysis, a full characterization concerning combustion efficiency and stability of the prototype chamber is possible. Furthermore, the data show full compliance with the expected operating requirements of the designated µ-scale gas turbine. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...] [article] Design and testing of a micromix combustor with recuperative wall cooling for a hydrogen fueled µ-scale gas turbine [texte imprimé] / Robinson, A. E., Auteur ; Funke, H. H.-W., Auteur ; Hendrick, P., Auteur . - 2011 . - 08 p. Génie Mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 08 p. Mots-clés : Gas  turbines  Remotely  operated  vehicles  Turbomachinery Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : For more than 1 decade up to now, there is an ongoing interest in small gas turbines downsized to microscale. With their high energy density, they offer a great potential as a substitute for today's unwieldy accumulators found in a variety of applications such as laptops, small tools, etc. But microscale gas turbines could not only be used for generating electricity, they could also produce thrust for powering small unmanned aerial vehicles or similar devices. Beneath all the great design challenges with the rotating parts of the turbomachinery at this small scale, another crucial item is in fact the combustion chamber needed for a safe and reliable operation. With the so-called regular micromix burning principle for hydrogen successfully downscaled in an initial combustion chamber prototype of 10 kW energy output, this paper describes a new design attempt aimed at the integration possibilities in a µ-scale gas turbine. For manufacturing the combustion chamber completely out of stainless steel components, a recuperative wall cooling was introduced to keep the temperatures in an acceptable range. Also a new way of an integrated ignition was developed. The detailed description of the prototype's design is followed by an in depth report about the test results. The experimental investigations comprise a set of mass flow variations, coupled with a variation of the equivalence ratio for each mass flow at different inlet temperatures and pressures. With the data obtained by an exhaust gas analysis, a full characterization concerning combustion efficiency and stability of the prototype chamber is possible. Furthermore, the data show full compliance with the expected operating requirements of the designated µ-scale gas turbine. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...]

Experimental investigations of pressure losses on the performance of a micro gas turbine system / Zanger, Jan in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 133 N° 8 (Août 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 09 p. Titre : Experimental investigations of pressure losses on the performance of a micro gas turbine system Type de document : texte imprimé Auteurs : Zanger, Jan, Auteur ; Widenhorn, Axel, Auteur ; Aigner, Manfred, Auteur Année de publication : 2011 Article en page(s) : 09 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Fuel  cell  power  plants  Gas  turbines  Hybrid  power  systems  Power  system  stability  Solid  oxide  fuel  cells Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Pressure losses between the compressor outlet and the turbine inlet are a major issue of overall efficiency and system stability for a solid oxide fuel cell/micro gas turbine (MGT) hybrid power plant system. The goal of this work is the detailed analysis of the effects of additional pressure losses on MGT performance in terms of steady-state and transient conditions. The experiments were performed using the micro gas turbine test rig at the German Aerospace Centre in Stuttgart using a butterfly control valve to apply additional pressure loss. This paper reports electric power and pressure characteristics at steady-state conditions as well as a new surge limit for this Turbec T100 micro gas turbine test rig. Furthermore, the effects of additional pressure loss on the compressor surge margin are quantified and a linear relation between the relative surge margin and additional pressure loss is shown. For transient variation of pressure loss at constant turbine speed, time delays are presented and an instability issue of the commercial gas turbine controller is discussed. Finally, bleed-air blow-off and reduction of the turbine outlet temperature are introduced as methods of increasing the surge margin. It is quantified that both methods have a substantial effect on the compressor surge margin. Furthermore, a comparison between both methods is given in terms of electric power output. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...] [article] Experimental investigations of pressure losses on the performance of a micro gas turbine system [texte imprimé] / Zanger, Jan, Auteur ; Widenhorn, Axel, Auteur ; Aigner, Manfred, Auteur . - 2011 . - 09 p. Génie Mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 09 p. Mots-clés : Fuel  cell  power  plants  Gas  turbines  Hybrid  power  systems  Power  system  stability  Solid  oxide  fuel  cells Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Pressure losses between the compressor outlet and the turbine inlet are a major issue of overall efficiency and system stability for a solid oxide fuel cell/micro gas turbine (MGT) hybrid power plant system. The goal of this work is the detailed analysis of the effects of additional pressure losses on MGT performance in terms of steady-state and transient conditions. The experiments were performed using the micro gas turbine test rig at the German Aerospace Centre in Stuttgart using a butterfly control valve to apply additional pressure loss. This paper reports electric power and pressure characteristics at steady-state conditions as well as a new surge limit for this Turbec T100 micro gas turbine test rig. Furthermore, the effects of additional pressure loss on the compressor surge margin are quantified and a linear relation between the relative surge margin and additional pressure loss is shown. For transient variation of pressure loss at constant turbine speed, time delays are presented and an instability issue of the commercial gas turbine controller is discussed. Finally, bleed-air blow-off and reduction of the turbine outlet temperature are introduced as methods of increasing the surge margin. It is quantified that both methods have a substantial effect on the compressor surge margin. Furthermore, a comparison between both methods is given in terms of electric power output. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...]

Transient pressure loss in compressor station piping systems / Klaus Brun in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 133 N° 8 (Août 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 09 p. Titre : Transient pressure loss in compressor station piping systems Type de document : texte imprimé Auteurs : Klaus Brun, Auteur ; Nored, Marybeth, Auteur ; Tweten, Dennis, Auteur Année de publication : 2011 Article en page(s) : 09 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Boundary  layers  Compressors  Navier-Stokes  equations  Pipe  flow Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : “Dynamic pressure loss” is often used to describe the added loss associated with the time varying components of an unsteady flow through a piping system in centrifugal and reciprocating compressor stations. Conventionally, dynamic pressure losses are determined by assuming a periodically pulsating 1D flow profile and calculating the transient pipe friction losses by multiplying a friction factor by the average flow dynamic pressure component. In reality, the dynamic pressure loss is more complex and is not a single component but consists of several different physical effects, which are affected by the piping arrangement, structural supports, piping diameter, and the level of unsteadiness in the flow stream. The pressure losses due to fluid-structure interactions represent one of these physical loss mechanisms and are presently the most misrepresented loss term. The dynamic pressure losses, dominated at times by the fluid-structure interactions, have not been previously quantified for transient flows in compressor piping systems. A number of experiments were performed by Southwest Research Institute (SwRI) utilizing an instrumented piping system in a compressor closed-loop facility to determine this loss component. Steady and dynamic pressure transducers and on-pipe accelerometers were utilized to study the dynamic pressure loss. This paper describes the findings from reciprocating compressor experiments and the various fluid modeling studies undertaken for the same piping system. The objective of the research was to quantitatively assess the individual pressure loss components, which contribute to dynamic pressure (nonsteady) loss based on their physical basis as described by the momentum equation. Results from these experiments were compared with steady-state and dynamic pressure loss predictions from 1D and 3D fluid models (utilizing both steady and transient flow conditions to quantify the associated loss terms). Comparisons between the fluid model predictions and experiments revealed that pressure losses associated with the piping fluid-structure interactions can be significant and may be unaccounted for by advanced 3D fluid models. These fluid-to-structure losses should not be ignored when predicting dynamic pressure loss. The results also indicated the ability of an advanced 1D Navier–Stokes solution at predicting inertial momentum losses. Correspondingly, the three-dimensional fluid models were able to capture boundary layer losses affected by 3D geometries. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...] [article] Transient pressure loss in compressor station piping systems [texte imprimé] / Klaus Brun, Auteur ; Nored, Marybeth, Auteur ; Tweten, Dennis, Auteur . - 2011 . - 09 p. Génie Mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 09 p. Mots-clés : Boundary  layers  Compressors  Navier-Stokes  equations  Pipe  flow Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : “Dynamic pressure loss” is often used to describe the added loss associated with the time varying components of an unsteady flow through a piping system in centrifugal and reciprocating compressor stations. Conventionally, dynamic pressure losses are determined by assuming a periodically pulsating 1D flow profile and calculating the transient pipe friction losses by multiplying a friction factor by the average flow dynamic pressure component. In reality, the dynamic pressure loss is more complex and is not a single component but consists of several different physical effects, which are affected by the piping arrangement, structural supports, piping diameter, and the level of unsteadiness in the flow stream. The pressure losses due to fluid-structure interactions represent one of these physical loss mechanisms and are presently the most misrepresented loss term. The dynamic pressure losses, dominated at times by the fluid-structure interactions, have not been previously quantified for transient flows in compressor piping systems. A number of experiments were performed by Southwest Research Institute (SwRI) utilizing an instrumented piping system in a compressor closed-loop facility to determine this loss component. Steady and dynamic pressure transducers and on-pipe accelerometers were utilized to study the dynamic pressure loss. This paper describes the findings from reciprocating compressor experiments and the various fluid modeling studies undertaken for the same piping system. The objective of the research was to quantitatively assess the individual pressure loss components, which contribute to dynamic pressure (nonsteady) loss based on their physical basis as described by the momentum equation. Results from these experiments were compared with steady-state and dynamic pressure loss predictions from 1D and 3D fluid models (utilizing both steady and transient flow conditions to quantify the associated loss terms). Comparisons between the fluid model predictions and experiments revealed that pressure losses associated with the piping fluid-structure interactions can be significant and may be unaccounted for by advanced 3D fluid models. These fluid-to-structure losses should not be ignored when predicting dynamic pressure loss. The results also indicated the ability of an advanced 1D Navier–Stokes solution at predicting inertial momentum losses. Correspondingly, the three-dimensional fluid models were able to capture boundary layer losses affected by 3D geometries. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...]

Instability and chaos of a flexible rotor all bearing system / Gupta, T. C. in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 133 N° 8 (Août 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 11 p. Titre : Instability and chaos of a flexible rotor all bearing system : an investigation on the influence of rotating imbalance and bearing clearance Type de document : texte imprimé Auteurs : Gupta, T. C., Auteur ; Gupta, K., Auteur ; Sehgal, D. K., Auteur Année de publication : 2011 Article en page(s) : 11 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Ball  bearings  Beams  (structures)  Lyapunov  methods  Matrix  algebra  Rotors  Stability Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : n this paper, a horizontal flexible rotor supported on two deep groove ball bearings is theoretically investigated for instability and chaos. The system is biperiodically excited. The two sources of excitation are rotating imbalance and self excitation due to varying compliance effect of ball bearing. A generalized Timoshenko beam finite element (FE) formulation, which can be used for both flexible and rigid rotor systems with equal effectiveness, is developed. The novel scheme proposed in the literature to analyze quasiperiodic response is coupled with the existing nonautonomous shooting method and is thus modified; the shooting method is used to obtain a steady state quasiperiodic solution. The eigenvalues of monodromy matrix provide information about stability and nature of bifurcation of the quasiperiodic solution. The maximum value of the Lyapunov exponent is used for quantitative measure of chaos in the dynamic response. The effect of three parameters, viz., rotating unbalance, bearing clearance, and rotor flexibility, on an unstable and chaotic behavior of a horizontal flexible rotor is studied. Interactive effects between the three parameters are examined in detail in respect of rotor system instability and chaos, and finally the range of parameters is established for the same. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...] [article] Instability and chaos of a flexible rotor all bearing system : an investigation on the influence of rotating imbalance and bearing clearance [texte imprimé] / Gupta, T. C., Auteur ; Gupta, K., Auteur ; Sehgal, D. K., Auteur . - 2011 . - 11 p. Génie Mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 11 p. Mots-clés : Ball  bearings  Beams  (structures)  Lyapunov  methods  Matrix  algebra  Rotors  Stability Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : n this paper, a horizontal flexible rotor supported on two deep groove ball bearings is theoretically investigated for instability and chaos. The system is biperiodically excited. The two sources of excitation are rotating imbalance and self excitation due to varying compliance effect of ball bearing. A generalized Timoshenko beam finite element (FE) formulation, which can be used for both flexible and rigid rotor systems with equal effectiveness, is developed. The novel scheme proposed in the literature to analyze quasiperiodic response is coupled with the existing nonautonomous shooting method and is thus modified; the shooting method is used to obtain a steady state quasiperiodic solution. The eigenvalues of monodromy matrix provide information about stability and nature of bifurcation of the quasiperiodic solution. The maximum value of the Lyapunov exponent is used for quantitative measure of chaos in the dynamic response. The effect of three parameters, viz., rotating unbalance, bearing clearance, and rotor flexibility, on an unstable and chaotic behavior of a horizontal flexible rotor is studied. Interactive effects between the three parameters are examined in detail in respect of rotor system instability and chaos, and finally the range of parameters is established for the same. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...]

A probabilistic framework for gas turbine engine materials with multiple types of anomalies / Enright, Michael P. in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 133 N° 8 (Août 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 10 p. Titre : A probabilistic framework for gas turbine engine materials with multiple types of anomalies Type de document : texte imprimé Auteurs : Enright, Michael P., Auteur ; McClung, R. Craig, Auteur Année de publication : 2011 Article en page(s) : 10 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Engines  Fault  tolerance  Gas  turbines  Hydraulic  turbines  Manufacturing  processes  Probability  Risk  analysis Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Some rotor-grade gas turbine engine materials may contain multiple types of anomalies such as voids and inclusions that can be introduced during the manufacturing process. The number and size of anomalies can be very different for the various anomaly types, each of which may lead to premature fracture. The probability of failure of a component with multiple anomaly types can be predicted using established system reliability methods provided that the failure probabilities associated with individual anomaly types are known. Unfortunately, these failure probabilities are often difficult to obtain in practice. In this paper, an approach is presented that provides treatment for engine materials with multiple anomalies of multiple types. It is based on a previous work that has been extended to address the overlap among anomaly type failure modes using the method of Kaplan–Meier and is illustrated for risk prediction of a nickel-based superalloy. The results can be used to predict the risk of general materials with multiple types of anomalies. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...] [article] A probabilistic framework for gas turbine engine materials with multiple types of anomalies [texte imprimé] / Enright, Michael P., Auteur ; McClung, R. Craig, Auteur . - 2011 . - 10 p. Génie Mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 10 p. Mots-clés : Engines  Fault  tolerance  Gas  turbines  Hydraulic  turbines  Manufacturing  processes  Probability  Risk  analysis Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Some rotor-grade gas turbine engine materials may contain multiple types of anomalies such as voids and inclusions that can be introduced during the manufacturing process. The number and size of anomalies can be very different for the various anomaly types, each of which may lead to premature fracture. The probability of failure of a component with multiple anomaly types can be predicted using established system reliability methods provided that the failure probabilities associated with individual anomaly types are known. Unfortunately, these failure probabilities are often difficult to obtain in practice. In this paper, an approach is presented that provides treatment for engine materials with multiple anomalies of multiple types. It is based on a previous work that has been extended to address the overlap among anomaly type failure modes using the method of Kaplan–Meier and is illustrated for risk prediction of a nickel-based superalloy. The results can be used to predict the risk of general materials with multiple types of anomalies. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...]

Rotordynamic characteristics of a five pad, rocker-pivot, tilting pad bearing in a load-on-pad configuration / Childs, Dara W. in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 133 N° 8 (Août 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 11 p. Titre : Rotordynamic characteristics of a five pad, rocker-pivot, tilting pad bearing in a load-on-pad configuration : comparisons to predictions and load-between-pad results Type de document : texte imprimé Auteurs : Childs, Dara W., Auteur ; Carter, Clint R., Auteur Année de publication : 2011 Article en page(s) : 11 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Damping  Machine  bearings  Rockets  Rotors  Turbomachinery Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Rotordynamic data are presented for a rocker-pivot tilting pad bearing in load-on-pad (LOP) configuration for (345–3101 kPa) unit loads and speeds from 4000 rpm to 13,000 rpm. The bearing was directly lubricated through a leading edge groove with five pads, 0.282 preload, 60% offset, 57.87 deg pad arc angle, 101.587 mm (3.9995 in.) rotor diameter, 0.1575 mm (0.0062 in.) diametral clearance, and 60.325 mm (2.375 in.) pad length. Measured results were reported for this bearing by Carter and Childs (2008, “Measurements Versus Predictions for the Rotordynamic Characteristics of a 5-Pad, Rocker-Pivot, Tilting-Pad Bearing in Load Between Pad Configuration,” ASME Paper No. GT2008-50069) in the load-between-pad (LBP) configuration. Results for the LOP are compared with predictions from a bulk-flow Navier–Stokes model (as utilized by San Andres (1991, “Effect of Eccentricity on the Force Response of a Hybrid Bearing,” STLE Tribol. Trans., 34, pp. 537–544)) and to the prior LBP results. Frequency effects on the dynamic-stiffness coefficients were investigated by applying dynamic-force excitation over a range of excitation frequencies. Generally, the direct real parts of the dynamic-stiffness coefficients could be modeled as quadratic functions of the excitation frequency, and accounted for by adding a mass matrix to the conventional [K][C] model to produce a frequency-independent [K][C][M] model. Measured added-mass terms in the loaded direction approached 60 kg. The static load direction in the tests was y. The direct stiffness coefficients Kyy and Kxx depend strongly on the applied unit load, more so than speed. They generally increased linearly with load, shifting to a quadratic dependence at higher unit loads. At lower unit loads, Kyy and Kxx increase monotonically with running speed. The experimental results were compared with predictions from a bulk-flow computational fluid dynamics analysis. Stiffness orthotropy was apparent in test results, significantly more than predicted, and it became more pronounced at the heavier unit loads. Measured Kyy values were consistently higher than predicted, and measured Kxx values were lower. Comparing the LOP results to prior measured LBP results for the same bearing, at higher loads, Kyy is significantly larger for the LOP configuration than LBP. Measured values for Kxx are about the same for LOP and LBP. At low unit loads, stiffness orthotropy defined as Kyy/Kxx is the same for LOP and LBP, progressively increasing with increasing unit loads. At the highest unit load, Kyy/Kxx=2.1 for LOP and 1.7 for LBP. Measured direct damping coefficients Cxx and Cyy were insensitive to changes in either load or speed, in contrast to predictions of marked Cyy sensitivity for changes in the load. Only at the highest test speed of 13,000 rpm were the direct damping coefficients adequately predicted. No frequency dependency was observed for the direct damping coefficients. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...] [article] Rotordynamic characteristics of a five pad, rocker-pivot, tilting pad bearing in a load-on-pad configuration : comparisons to predictions and load-between-pad results [texte imprimé] / Childs, Dara W., Auteur ; Carter, Clint R., Auteur . - 2011 . - 11 p. Génie Mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 11 p. Mots-clés : Damping  Machine  bearings  Rockets  Rotors  Turbomachinery Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Rotordynamic data are presented for a rocker-pivot tilting pad bearing in load-on-pad (LOP) configuration for (345–3101 kPa) unit loads and speeds from 4000 rpm to 13,000 rpm. The bearing was directly lubricated through a leading edge groove with five pads, 0.282 preload, 60% offset, 57.87 deg pad arc angle, 101.587 mm (3.9995 in.) rotor diameter, 0.1575 mm (0.0062 in.) diametral clearance, and 60.325 mm (2.375 in.) pad length. Measured results were reported for this bearing by Carter and Childs (2008, “Measurements Versus Predictions for the Rotordynamic Characteristics of a 5-Pad, Rocker-Pivot, Tilting-Pad Bearing in Load Between Pad Configuration,” ASME Paper No. GT2008-50069) in the load-between-pad (LBP) configuration. Results for the LOP are compared with predictions from a bulk-flow Navier–Stokes model (as utilized by San Andres (1991, “Effect of Eccentricity on the Force Response of a Hybrid Bearing,” STLE Tribol. Trans., 34, pp. 537–544)) and to the prior LBP results. Frequency effects on the dynamic-stiffness coefficients were investigated by applying dynamic-force excitation over a range of excitation frequencies. Generally, the direct real parts of the dynamic-stiffness coefficients could be modeled as quadratic functions of the excitation frequency, and accounted for by adding a mass matrix to the conventional [K][C] model to produce a frequency-independent [K][C][M] model. Measured added-mass terms in the loaded direction approached 60 kg. The static load direction in the tests was y. The direct stiffness coefficients Kyy and Kxx depend strongly on the applied unit load, more so than speed. They generally increased linearly with load, shifting to a quadratic dependence at higher unit loads. At lower unit loads, Kyy and Kxx increase monotonically with running speed. The experimental results were compared with predictions from a bulk-flow computational fluid dynamics analysis. Stiffness orthotropy was apparent in test results, significantly more than predicted, and it became more pronounced at the heavier unit loads. Measured Kyy values were consistently higher than predicted, and measured Kxx values were lower. Comparing the LOP results to prior measured LBP results for the same bearing, at higher loads, Kyy is significantly larger for the LOP configuration than LBP. Measured values for Kxx are about the same for LOP and LBP. At low unit loads, stiffness orthotropy defined as Kyy/Kxx is the same for LOP and LBP, progressively increasing with increasing unit loads. At the highest unit load, Kyy/Kxx=2.1 for LOP and 1.7 for LBP. Measured direct damping coefficients Cxx and Cyy were insensitive to changes in either load or speed, in contrast to predictions of marked Cyy sensitivity for changes in the load. Only at the highest test speed of 13,000 rpm were the direct damping coefficients adequately predicted. No frequency dependency was observed for the direct damping coefficients. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...]

CFD modeling and LDA measurements for the air-flow in an aero engine front bearing chamber / Aidarinis, J. in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 133 N° 8 (Août 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 08 p. Titre : CFD modeling and LDA measurements for the air-flow in an aero engine front bearing chamber Type de document : texte imprimé Auteurs : Aidarinis, J., Auteur ; Missirlis, D., Auteur ; Yakinthos, K., Auteur Année de publication : 2011 Article en page(s) : 08 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Computational  fluid  dynamics  Laser  Doppler  anemometry  Lubrication  Machine  bearings  Shafts Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The continuous development of aero engines toward lighter but yet more compact designs, without decreasing their efficiency, has led to gradually increasing demands on the lubrication system, such as the bearing chambers of an aero engine. For this reason, it is of particular importance to increase the level of understanding of the flow field inside the bearing chamber in order to optimize its design and improve its performance. The flow field inside a bearing chamber is complicated since there is a strong interaction between the sealing air-flow and the flow of lubrication oil, and both of them are affected by and interacting with the geometry of the chamber and the rotating shaft. In order to understand the flow field development and, as a next step, to optimize the aero engine bearing chamber performance, in relation to the lubrication and heat transfer capabilities, the behavior of this interaction must be investigated. In this work, an investigation of the air-flow field development inside the front bearing chamber of an aero engine is attempted. The front bearing chamber is divided into two separate sections. The flow from the first section passes through the bearing and the bearing holding structure to the second one where the vent and the scavenging system are located. The investigation was performed with the combined use of experimental measurements and computational fluid dynamics (CFD) modeling. The experimental measurements were carried out using a laser Doppler anemometry system in an experimental rig, which consists of a 1:1 model of the front bearing chamber of an aero engine. Tests were carried out at real operating conditions both for the air-flow and for the lubricant oil-flow and for a range of shaft rotating speeds. The CFD modeling was performed using a commercial CFD package. Particularly, the air-flow through the bearing itself was modeled, adopting a porous medium technique, the parameters of which were developed in conjunction with the experiments. A satisfactory quantitative agreement between the experimental measurements and the CFD computations was achieved. At the same time, the effect of the important parameters such as the air and oil mass flow, together with the shaft rotational speed, and the effect of the chamber geometry were identified. The conclusions can be exploited in future attempts in combination with the CFD model developed in order to optimize the efficiency of the lubrication and cooling system. The latter forms the main target of this work, which is the development of a useful engineering tool capable of predicting the flow field inside the aero engine bearing, which can be used subsequently for optimization purposes. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...] [article] CFD modeling and LDA measurements for the air-flow in an aero engine front bearing chamber [texte imprimé] / Aidarinis, J., Auteur ; Missirlis, D., Auteur ; Yakinthos, K., Auteur . - 2011 . - 08 p. Génie Mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 08 p. Mots-clés : Computational  fluid  dynamics  Laser  Doppler  anemometry  Lubrication  Machine  bearings  Shafts Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The continuous development of aero engines toward lighter but yet more compact designs, without decreasing their efficiency, has led to gradually increasing demands on the lubrication system, such as the bearing chambers of an aero engine. For this reason, it is of particular importance to increase the level of understanding of the flow field inside the bearing chamber in order to optimize its design and improve its performance. The flow field inside a bearing chamber is complicated since there is a strong interaction between the sealing air-flow and the flow of lubrication oil, and both of them are affected by and interacting with the geometry of the chamber and the rotating shaft. In order to understand the flow field development and, as a next step, to optimize the aero engine bearing chamber performance, in relation to the lubrication and heat transfer capabilities, the behavior of this interaction must be investigated. In this work, an investigation of the air-flow field development inside the front bearing chamber of an aero engine is attempted. The front bearing chamber is divided into two separate sections. The flow from the first section passes through the bearing and the bearing holding structure to the second one where the vent and the scavenging system are located. The investigation was performed with the combined use of experimental measurements and computational fluid dynamics (CFD) modeling. The experimental measurements were carried out using a laser Doppler anemometry system in an experimental rig, which consists of a 1:1 model of the front bearing chamber of an aero engine. Tests were carried out at real operating conditions both for the air-flow and for the lubricant oil-flow and for a range of shaft rotating speeds. The CFD modeling was performed using a commercial CFD package. Particularly, the air-flow through the bearing itself was modeled, adopting a porous medium technique, the parameters of which were developed in conjunction with the experiments. A satisfactory quantitative agreement between the experimental measurements and the CFD computations was achieved. At the same time, the effect of the important parameters such as the air and oil mass flow, together with the shaft rotational speed, and the effect of the chamber geometry were identified. The conclusions can be exploited in future attempts in combination with the CFD model developed in order to optimize the efficiency of the lubrication and cooling system. The latter forms the main target of this work, which is the development of a useful engineering tool capable of predicting the flow field inside the aero engine bearing, which can be used subsequently for optimization purposes. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...]

Correlation between speciated hydrocarbon emissions and flame ionization detector response for gasoline/alcohol blends / Wallner, Thomas in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 133 N° 8 (Août 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 08 p. Titre : Correlation between speciated hydrocarbon emissions and flame ionization detector response for gasoline/alcohol blends Type de document : texte imprimé Auteurs : Wallner, Thomas, Auteur Année de publication : 2011 Article en page(s) : 08 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Air  pollution  Biofuel  Carbon  compounds  Flames  Fourier  transform  spectra  Instrumentation  Nitrogen  compounds  Petroleum Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The U.S. renewable fuel standard has made it a requirement to increase the production of ethanol and advanced biofuels to 36 billion by 2022. Ethanol will be capped at 15 billion, which leaves 21 billion to come from other sources such as butanol. Butanol has a higher energy density and lower affinity for water than ethanol. Moreover, alcohol fueled engines in general have been shown to positively affect engine-out emissions of oxides of nitrogen and carbon monoxide compared with their gasoline fueled counterparts. In light of these developments, the variety and blend levels of oxygenated constituents is likely to increase in the foreseeable future. The effect on engine-out emissions for total hydrocarbons is less clear due to the relative insensitivity of the flame ionization detector (FID) toward alcohols and aldehydes. It is well documented that hydrocarbon (HC) measurement using a conventional FID in the presence of oxygenates in the engine exhaust stream can lead to a misinterpretation of HC emissions trends for alcohol fuel blends. Characterization of the exhaust stream for all expected hydrocarbon constituents is required to accurately determine the actual concentration of unburned fuel components in the exhaust. In addition to a conventional exhaust emissions bench, this characterization requires supplementary instrumentation capable of hydrocarbon speciation and response factor independent quantification. Although required for certification testing, this sort of instrumentation is not yet widely available in engine development facilities. Therefore, an attempt is made to empirically determine FID correction factors for oxygenate fuels. Exhaust emissions of an engine fueled with several blends of gasoline and ethanol, n-butanol and iso-Butanol were characterized using both a conventional FID and a Fourier transform infrared. Based on these results, a response factor predicting the actual hydrocarbon emissions based solely on FID results as a function of alcohol type and content is presented. Finally, the correlation derived from data presented in this study is compared with equations and results found in the literature. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...] [article] Correlation between speciated hydrocarbon emissions and flame ionization detector response for gasoline/alcohol blends [texte imprimé] / Wallner, Thomas, Auteur . - 2011 . - 08 p. Génie Mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 08 p. Mots-clés : Air  pollution  Biofuel  Carbon  compounds  Flames  Fourier  transform  spectra  Instrumentation  Nitrogen  compounds  Petroleum Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The U.S. renewable fuel standard has made it a requirement to increase the production of ethanol and advanced biofuels to 36 billion by 2022. Ethanol will be capped at 15 billion, which leaves 21 billion to come from other sources such as butanol. Butanol has a higher energy density and lower affinity for water than ethanol. Moreover, alcohol fueled engines in general have been shown to positively affect engine-out emissions of oxides of nitrogen and carbon monoxide compared with their gasoline fueled counterparts. In light of these developments, the variety and blend levels of oxygenated constituents is likely to increase in the foreseeable future. The effect on engine-out emissions for total hydrocarbons is less clear due to the relative insensitivity of the flame ionization detector (FID) toward alcohols and aldehydes. It is well documented that hydrocarbon (HC) measurement using a conventional FID in the presence of oxygenates in the engine exhaust stream can lead to a misinterpretation of HC emissions trends for alcohol fuel blends. Characterization of the exhaust stream for all expected hydrocarbon constituents is required to accurately determine the actual concentration of unburned fuel components in the exhaust. In addition to a conventional exhaust emissions bench, this characterization requires supplementary instrumentation capable of hydrocarbon speciation and response factor independent quantification. Although required for certification testing, this sort of instrumentation is not yet widely available in engine development facilities. Therefore, an attempt is made to empirically determine FID correction factors for oxygenate fuels. Exhaust emissions of an engine fueled with several blends of gasoline and ethanol, n-butanol and iso-Butanol were characterized using both a conventional FID and a Fourier transform infrared. Based on these results, a response factor predicting the actual hydrocarbon emissions based solely on FID results as a function of alcohol type and content is presented. Finally, the correlation derived from data presented in this study is compared with equations and results found in the literature. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...]

The design of an ambient neutron dose-equivalent meter / Wenming, Xia in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 133 N° 8 (Août 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 04 p. Titre : The design of an ambient neutron dose-equivalent meter Type de document : texte imprimé Auteurs : Wenming, Xia, Auteur ; Mingchun, Jia, Auteur ; Zhirong, Guo, Auteur Année de publication : 2011 Article en page(s) : 04 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Dosimeters  Monte  Carlo  methods Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : At present, most of the developed neutron dosimeters used to measure the neutron ambient dose-equivalent that has a moderator with a single counter, applied in neutron radiation fields within large range energies from thermal to MeV neutrons, are not a satisfaction to energy response. The purpose of this article is to design a suitable neutron dosimeter for radiation protection purpose. In order to overcome the disadvantage of the energy response of the neutron dosimeters combining a single sphere with a single counter, three spheres and three 3He counters were combined for the detector design. The response function of moderators with different thicknesses combined with SP9 3He counters were calculated with Monte Carlo code MCNP 4C. The selection of three different thicknesses of the moderating polyethylene sphere was done with a MATLAB program. A suitable combination of three different thicknesses was confirmed for the detector design. The electronic system of the neutron dosimeter was introduced. The results of ambient dose-equivalent per unit fluence in different radiation areas were calculated, analyzed, and compared with the values recommended in the ISO standard. The calculated result explains that it is very significant to this design of neutron dosimeter; it may be applied to the monitor of the ambient dose in the neutron radiation fields, improving at present the status of the energy response of neutron dosimeters. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...] [article] The design of an ambient neutron dose-equivalent meter [texte imprimé] / Wenming, Xia, Auteur ; Mingchun, Jia, Auteur ; Zhirong, Guo, Auteur . - 2011 . - 04 p. Génie Mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 04 p. Mots-clés : Dosimeters  Monte  Carlo  methods Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : At present, most of the developed neutron dosimeters used to measure the neutron ambient dose-equivalent that has a moderator with a single counter, applied in neutron radiation fields within large range energies from thermal to MeV neutrons, are not a satisfaction to energy response. The purpose of this article is to design a suitable neutron dosimeter for radiation protection purpose. In order to overcome the disadvantage of the energy response of the neutron dosimeters combining a single sphere with a single counter, three spheres and three 3He counters were combined for the detector design. The response function of moderators with different thicknesses combined with SP9 3He counters were calculated with Monte Carlo code MCNP 4C. The selection of three different thicknesses of the moderating polyethylene sphere was done with a MATLAB program. A suitable combination of three different thicknesses was confirmed for the detector design. The electronic system of the neutron dosimeter was introduced. The results of ambient dose-equivalent per unit fluence in different radiation areas were calculated, analyzed, and compared with the values recommended in the ISO standard. The calculated result explains that it is very significant to this design of neutron dosimeter; it may be applied to the monitor of the ambient dose in the neutron radiation fields, improving at present the status of the energy response of neutron dosimeters. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...]

Removal of uranium from aqueous solution by chitosan and ferrous ions / Wang, Jing-song in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 133 N° 8 (Août 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 03 p. Titre : Removal of uranium from aqueous solution by chitosan and ferrous ions Type de document : texte imprimé Auteurs : Wang, Jing-song, Auteur ; Bao, Zheng-lei, Auteur ; Chen, Si-guang, Auteur ; Yang, Jin-hui, Auteur Année de publication : 2011 Article en page(s) : 03 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Adsorption  Organic  compounds  pH  Precipitation  Uranium  Wastewater  treatment Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : This study focuses on developing a new method to remove uranium from aqueous solution. Chitosan and ferrous ions were used together to remove uranium ions from aqueous solution. Through two-step pH adjustment, the uptake behavior of chitosan and ferrous ions toward uranium in aqueous solution using batch systems was studied in different experimental conditions. The experimental results indicated that the removal of uranium by the synergetic effect of chitosan and ferrous ions was more effective than the way of adsorbing uranium ions by chitosan alone. Under the given experimental conditions, the concentration of the residual uranium in the effluent after the chitosan and ferrous ion treatment could meet the discharge standard (<0.05 mg l−1) when the initial concentration of uranium ions was 10 mg l−1 or 100 mg l−1. The synergetic effect of chitosan and ferrous ions, including adsorption, coacervation, and coprecipitation, was responsible for the high removal rate of uranium. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...] [article] Removal of uranium from aqueous solution by chitosan and ferrous ions [texte imprimé] / Wang, Jing-song, Auteur ; Bao, Zheng-lei, Auteur ; Chen, Si-guang, Auteur ; Yang, Jin-hui, Auteur . - 2011 . - 03 p. Génie Mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 03 p. Mots-clés : Adsorption  Organic  compounds  pH  Precipitation  Uranium  Wastewater  treatment Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : This study focuses on developing a new method to remove uranium from aqueous solution. Chitosan and ferrous ions were used together to remove uranium ions from aqueous solution. Through two-step pH adjustment, the uptake behavior of chitosan and ferrous ions toward uranium in aqueous solution using batch systems was studied in different experimental conditions. The experimental results indicated that the removal of uranium by the synergetic effect of chitosan and ferrous ions was more effective than the way of adsorbing uranium ions by chitosan alone. Under the given experimental conditions, the concentration of the residual uranium in the effluent after the chitosan and ferrous ion treatment could meet the discharge standard (<0.05 mg l−1) when the initial concentration of uranium ions was 10 mg l−1 or 100 mg l−1. The synergetic effect of chitosan and ferrous ions, including adsorption, coacervation, and coprecipitation, was responsible for the high removal rate of uranium. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...]

A parametric study of fuel lattice design for HTR-10 / Wang, Meng-Jen in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 133 N° 8 (Août 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 04 p. Titre : A parametric study of fuel lattice design for HTR-10 Type de document : texte imprimé Auteurs : Wang, Meng-Jen, Auteur ; Peir, Jinn-Jer, Auteur ; Chi, Chen-Wei, Auteur Année de publication : 2011 Article en page(s) : 04 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Gas  cooled  reactors  Uranium  Aqueous  Chitosan  Ferrous  Discharge  standard Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : In this study, the multiplication factor and neutron spectrum behaviors were investigated against the moderator-to-fuel ratio, the fuel loading height, and the detector location in high-temperature gas-cooled reactor (HTR)-10. The MCNP5 computer code (version 1.51) was employed to perform all the simulation computations. The results revealed that the multiplication factor varies significantly depending on the moderator-to-fuel ratio and the fuel loading height due to the competition among the neutron moderation and absorption abilities of the moderator as well as the neutron production ability of the fuel. Due to its inherent stability, HTR-10 is deliberately designed such that the multiplication factor decreases and the neutron spectrum softens as the moderator-to-fuel ratio increases. The average neutron energy level in the HTR-10 fuel balls is approximately 240 keV and ranges from smallest to largest at the middle, bottom, and top of the reactor core, respectively. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...] [article] A parametric study of fuel lattice design for HTR-10 [texte imprimé] / Wang, Meng-Jen, Auteur ; Peir, Jinn-Jer, Auteur ; Chi, Chen-Wei, Auteur . - 2011 . - 04 p. Génie Mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 8 (Août 2011) . - 04 p. Mots-clés : Gas  cooled  reactors  Uranium  Aqueous  Chitosan  Ferrous  Discharge  standard Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : In this study, the multiplication factor and neutron spectrum behaviors were investigated against the moderator-to-fuel ratio, the fuel loading height, and the detector location in high-temperature gas-cooled reactor (HTR)-10. The MCNP5 computer code (version 1.51) was employed to perform all the simulation computations. The results revealed that the multiplication factor varies significantly depending on the moderator-to-fuel ratio and the fuel loading height due to the competition among the neutron moderation and absorption abilities of the moderator as well as the neutron production ability of the fuel. Due to its inherent stability, HTR-10 is deliberately designed such that the multiplication factor decreases and the neutron spectrum softens as the moderator-to-fuel ratio increases. The average neutron energy level in the HTR-10 fuel balls is approximately 240 keV and ranges from smallest to largest at the middle, bottom, and top of the reactor core, respectively. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...]

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