Dépouillements

Tension-compression fatigue of a SiC/SiC ceramic matrix composite at elevated temperature / M. B. Ruggles-Wrenn in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 134 N° 9 (Septembre 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 06 p. Titre : Tension-compression fatigue of a SiC/SiC ceramic matrix composite at elevated temperature Type de document : texte imprimé Auteurs : M. B. Ruggles-Wrenn, Auteur ; T. P. Jones, Auteur Année de publication : 2012 Article en page(s) : 06 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Tension-compression  fatigue  Nonoxide  ceramic  composite  Chemical  vapor  infiltration Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Tension-compression fatigue behavior of a nonoxide ceramic composite with a multilayered matrix was investigated at 1200 °C in laboratory air. The composite was produced via chemical vapor infiltration (CVI). The composite had an oxidation inhibited matrix, which consisted of alternating layers of silicon carbide and boron carbide and was reinforced with laminated Hi-NicalonTM fibers woven in an eight-harness-satin weave (8HSW). Fiber preforms had pyrolytic carbon fiber coating with boron carbon overlay applied. Tension-compression fatigue behavior was studied for fatigue stresses ranging from 80 to 200 MPa at a frequency of 1.0 Hz. The R ratio (minimum stress to maximum stress) was −1.0. Fatigue run-out was defined as 2 × 105 cycles. Fatigue limit was 80 MPa. Specimens that achieved fatigue run-out were subjected to tensile tests to failure to characterize the retained tensile properties. The material retained 100% of its tensile strength. Reductions in tensile modulus and in compressive modulus were negligible. Composite microstructure, as well as damage and failure mechanisms were investigated. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...] [article] Tension-compression fatigue of a SiC/SiC ceramic matrix composite at elevated temperature [texte imprimé] / M. B. Ruggles-Wrenn, Auteur ; T. P. Jones, Auteur . - 2012 . - 06 p. Génie mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 06 p. Mots-clés : Tension-compression  fatigue  Nonoxide  ceramic  composite  Chemical  vapor  infiltration Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Tension-compression fatigue behavior of a nonoxide ceramic composite with a multilayered matrix was investigated at 1200 °C in laboratory air. The composite was produced via chemical vapor infiltration (CVI). The composite had an oxidation inhibited matrix, which consisted of alternating layers of silicon carbide and boron carbide and was reinforced with laminated Hi-NicalonTM fibers woven in an eight-harness-satin weave (8HSW). Fiber preforms had pyrolytic carbon fiber coating with boron carbon overlay applied. Tension-compression fatigue behavior was studied for fatigue stresses ranging from 80 to 200 MPa at a frequency of 1.0 Hz. The R ratio (minimum stress to maximum stress) was −1.0. Fatigue run-out was defined as 2 × 105 cycles. Fatigue limit was 80 MPa. Specimens that achieved fatigue run-out were subjected to tensile tests to failure to characterize the retained tensile properties. The material retained 100% of its tensile strength. Reductions in tensile modulus and in compressive modulus were negligible. Composite microstructure, as well as damage and failure mechanisms were investigated. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...]

Combustion performance in a semiclosed cycle gas turbine for IGCC fired with CO-rich syngas and oxy-recirculated exhaust streams / Takeharu Hasegawa in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 134 N° 9 (Septembre 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 10 p. Titre : Combustion performance in a semiclosed cycle gas turbine for IGCC fired with CO-rich syngas and oxy-recirculated exhaust streams Type de document : texte imprimé Auteurs : Takeharu Hasegawa, Auteur Année de publication : 2012 Article en page(s) : 10 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : CO-rich  gasified  coal  fuel  Gas  turbine  Oxy-fuel  integrated  coal  gasification  combined  cycle  (IGCC)  Power  generation  system  Stoichiometric  combustion  CO2  capture Résumé : Our study found that burning a CO-rich gasified coal fuel, derived from an oxygen–CO2 blown gasifier, with oxygen under stoichiometric conditions in a closed cycle gas turbine produced a highly-efficient, oxy-fuel integrated coal gasification combined cycle (IGCC) power generation system with CO2 capture. We diluted stoichiometric combustion with recycled gas turbine exhaust and adjusted for given temperatures. Some of the exhaust was used to feed coal into the gasifier. In doing so, we found it necessary to minimize not only CO and H2 of unburned fuel constituents but also residual O2, not consumed in the gas turbine combustion process. In this study, we examined the emission characteristics of gasified-fueled stoichiometric combustion with oxygen through numerical analysis based on reaction kinetics. Furthermore, we investigated the reaction characteristics of reactant gases of CO, H2, and O2 remaining in the recirculating gas turbine exhaust using present numerical procedures. As a result, we were able to clarify that since fuel oxidation reaction is inhibited due to reasons of exhaust recirculation and lower oxygen partial pressure, CO oxidization is very sluggish and combustion reaction does not reach equilibrium at the combustor exit. In the case of a combustor exhaust temperature of 1573 K (1300 °C), we estimated that high CO exhaust emissions of about a few percent, in tens of milliseconds, corresponded to the combustion gas residence time in the gas turbine combustor. Combustion efficiency was estimated to reach only about 76%, which was a lower value compared to H2/O2-fired combustion while residual O2 in exhaust was 2.5 vol%, or five times as much as the equilibrium concentration. On the other hand, unburned constituents in an expansion turbine exhaust were slowed to oxidize in a heat recovery steam generator (HRSG) flue processing, and exhaust gases reached equilibrium conditions. In this regard, however, reaction heat in HRSG could not devote enough energy for combined cycle thermal efficiency, making advanced combustion technology necessary for achieving highly efficient, oxy-fuel IGCC. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...] [article] Combustion performance in a semiclosed cycle gas turbine for IGCC fired with CO-rich syngas and oxy-recirculated exhaust streams [texte imprimé] / Takeharu Hasegawa, Auteur . - 2012 . - 10 p. Génie mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 10 p. Mots-clés : CO-rich  gasified  coal  fuel  Gas  turbine  Oxy-fuel  integrated  coal  gasification  combined  cycle  (IGCC)  Power  generation  system  Stoichiometric  combustion  CO2  capture Résumé : Our study found that burning a CO-rich gasified coal fuel, derived from an oxygen–CO2 blown gasifier, with oxygen under stoichiometric conditions in a closed cycle gas turbine produced a highly-efficient, oxy-fuel integrated coal gasification combined cycle (IGCC) power generation system with CO2 capture. We diluted stoichiometric combustion with recycled gas turbine exhaust and adjusted for given temperatures. Some of the exhaust was used to feed coal into the gasifier. In doing so, we found it necessary to minimize not only CO and H2 of unburned fuel constituents but also residual O2, not consumed in the gas turbine combustion process. In this study, we examined the emission characteristics of gasified-fueled stoichiometric combustion with oxygen through numerical analysis based on reaction kinetics. Furthermore, we investigated the reaction characteristics of reactant gases of CO, H2, and O2 remaining in the recirculating gas turbine exhaust using present numerical procedures. As a result, we were able to clarify that since fuel oxidation reaction is inhibited due to reasons of exhaust recirculation and lower oxygen partial pressure, CO oxidization is very sluggish and combustion reaction does not reach equilibrium at the combustor exit. In the case of a combustor exhaust temperature of 1573 K (1300 °C), we estimated that high CO exhaust emissions of about a few percent, in tens of milliseconds, corresponded to the combustion gas residence time in the gas turbine combustor. Combustion efficiency was estimated to reach only about 76%, which was a lower value compared to H2/O2-fired combustion while residual O2 in exhaust was 2.5 vol%, or five times as much as the equilibrium concentration. On the other hand, unburned constituents in an expansion turbine exhaust were slowed to oxidize in a heat recovery steam generator (HRSG) flue processing, and exhaust gases reached equilibrium conditions. In this regard, however, reaction heat in HRSG could not devote enough energy for combined cycle thermal efficiency, making advanced combustion technology necessary for achieving highly efficient, oxy-fuel IGCC. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...]

Integrated combustor turbine design for improved aerothermal performance / Altug M. Basol in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 134 N° 9 (Septembre 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 08 p. Titre : Integrated combustor turbine design for improved aerothermal performance : effect of dilution air control Type de document : texte imprimé Auteurs : Altug M. Basol, Auteur ; Regina Kai, Auteur ; Anestis I. Kalfas, Auteur Année de publication : 2012 Article en page(s) : 08 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Dilution  air  control  Combustor  turbine  Aerothermal  performance Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The effect of dilution air control in a combustor on the heat load distribution of an axial turbine with nonaxisymmetric endwall profiling is examined. Endwall profiling is a more common design feature in new engine types, due to its effectiveness in reducing secondary flows and their associated losses. In the present work, the effect of dilution air control is examined by using two different circumferentially nonuniform hot-streak shapes; the two cases differ in their spanwise extents either side of the stator and, therefore, represent different approaches for dilution air control. This numerical study details the impact of these two different strategies for dilution air control on the rotor blade heat load distribution. The inlet boundary conditions simulate the experiment that is conducted in the axial research turbine facility LISA at ETH Zurich. A circumferential nonuniformity in the spanwise migration pattern of the hot streak inside the stator is observed that is found to be alleviated by the effect of the endwall profiling. Due to the observed spanwise migration pattern inside the stator the two hot-streak cases result in considerably different heat load distributions on the rotor blade, emphasizing the importance of the integrated combustor turbine approach. Finally, the implications for dilution air control on the liner are discussed for the realization of the simulated hot-streak shapes in real combustors. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...] [article] Integrated combustor turbine design for improved aerothermal performance : effect of dilution air control [texte imprimé] / Altug M. Basol, Auteur ; Regina Kai, Auteur ; Anestis I. Kalfas, Auteur . - 2012 . - 08 p. Génie mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 08 p. Mots-clés : Dilution  air  control  Combustor  turbine  Aerothermal  performance Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The effect of dilution air control in a combustor on the heat load distribution of an axial turbine with nonaxisymmetric endwall profiling is examined. Endwall profiling is a more common design feature in new engine types, due to its effectiveness in reducing secondary flows and their associated losses. In the present work, the effect of dilution air control is examined by using two different circumferentially nonuniform hot-streak shapes; the two cases differ in their spanwise extents either side of the stator and, therefore, represent different approaches for dilution air control. This numerical study details the impact of these two different strategies for dilution air control on the rotor blade heat load distribution. The inlet boundary conditions simulate the experiment that is conducted in the axial research turbine facility LISA at ETH Zurich. A circumferential nonuniformity in the spanwise migration pattern of the hot streak inside the stator is observed that is found to be alleviated by the effect of the endwall profiling. Due to the observed spanwise migration pattern inside the stator the two hot-streak cases result in considerably different heat load distributions on the rotor blade, emphasizing the importance of the integrated combustor turbine approach. Finally, the implications for dilution air control on the liner are discussed for the realization of the simulated hot-streak shapes in real combustors. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...]

Measurement of flame frequency response functions under exhaust gas recirculation conditions / Joseph Ranalli in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 134 N° 9 (Septembre 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 10 p. Titre : Measurement of flame frequency response functions under exhaust gas recirculation conditions Type de document : texte imprimé Auteurs : Joseph Ranalli, Auteur ; Don Ferguson, Auteur Année de publication : 2012 Article en page(s) : 10 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Exhaust  gas  recirculation  Thermoacoustic  instabilities  Flame  transfer  functions Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Exhaust gas recirculation has been proposed as a potential strategy for reducing the cost and efficiency penalty associated with postcombustion carbon capture. However, this approach may cause as-yet unresolved effects on the combustion process, including additional potential for the occurrence of thermoacoustic instabilities. Flame dynamics, characterized by the flame transfer function, were measured in traditional swirl stabilized and low-swirl injector combustor configurations, subject to exhaust gas circulation simulated by N2 and CO2 dilution. The flame transfer functions exhibited behavior consistent with a low-pass filter and showed phase dominated by delay. Flame transfer function frequencies were nondimensionalized using Strouhal number to highlight the convective nature of this delay. Dilution was observed to influence the dynamics primarily through its role in changing the size of the flame, indicating that it plays a similar role in determining the dynamics as changes in the equivalence ratio. Notchlike features in the flame transfer function were shown to be related to interference behaviors associated with the convective nature of the flame response. Some similarities between the two stabilization configurations proved limiting and generalization of the physical behaviors will require additional investigation. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...] [article] Measurement of flame frequency response functions under exhaust gas recirculation conditions [texte imprimé] / Joseph Ranalli, Auteur ; Don Ferguson, Auteur . - 2012 . - 10 p. Génie mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 10 p. Mots-clés : Exhaust  gas  recirculation  Thermoacoustic  instabilities  Flame  transfer  functions Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Exhaust gas recirculation has been proposed as a potential strategy for reducing the cost and efficiency penalty associated with postcombustion carbon capture. However, this approach may cause as-yet unresolved effects on the combustion process, including additional potential for the occurrence of thermoacoustic instabilities. Flame dynamics, characterized by the flame transfer function, were measured in traditional swirl stabilized and low-swirl injector combustor configurations, subject to exhaust gas circulation simulated by N2 and CO2 dilution. The flame transfer functions exhibited behavior consistent with a low-pass filter and showed phase dominated by delay. Flame transfer function frequencies were nondimensionalized using Strouhal number to highlight the convective nature of this delay. Dilution was observed to influence the dynamics primarily through its role in changing the size of the flame, indicating that it plays a similar role in determining the dynamics as changes in the equivalence ratio. Notchlike features in the flame transfer function were shown to be related to interference behaviors associated with the convective nature of the flame response. Some similarities between the two stabilization configurations proved limiting and generalization of the physical behaviors will require additional investigation. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...]

An integrated approach for the multidisciplinary design of optimum rotorcraft operations / Ioannis Goulos in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 134 N° 9 (Septembre 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 10 p. Titre : An integrated approach for the multidisciplinary design of optimum rotorcraft operations Type de document : texte imprimé Auteurs : Ioannis Goulos, Auteur ; Pachidis, Vassilios, Auteur ; Roberto d'Ippolito, Auteur Année de publication : 2012 Article en page(s) : 10 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Optimum  rotorcraft  operations Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : This work focuses on the development and application of a generic methodology targeting the design of optimum rotorcraft operations in terms of fuel burn, gaseous emissions, and ground noise impact. An integrated tool capable of estimating the performance and emitted noise of any defined rotorcraft configuration within any designated mission has been deployed. A comprehensive and cost-effective optimization strategy has been structured. The methodology has been applied to two generic, baseline missions representative of current rotorcraft operations. Optimally designed operations for fuel burn, gaseous emissions, and ground noise impact have been obtained. A comparative evaluation has been waged between the acquired optimum designs. The respective trade-off arising from the incorporation of flight paths optimized for different objectives has been quantified. Pareto front derived models for fuel burn and emitted noise have been structured for each mission. The Pareto models have been subsequently deployed for the design of operations optimized in a multidisciplinary manner. The results have shown that the proposed methodology is promising with regards to achieving simultaneous reduction in fuel burn, gaseous emissions, and ground noise impact for any defined mission. The obtainable reductions are found to be dependent on the designated mission. Finally, the potential to design optimum operations in a multidisciplinary fashion using only a single design criterion is demonstrated. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...] [article] An integrated approach for the multidisciplinary design of optimum rotorcraft operations [texte imprimé] / Ioannis Goulos, Auteur ; Pachidis, Vassilios, Auteur ; Roberto d'Ippolito, Auteur . - 2012 . - 10 p. Génie mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 10 p. Mots-clés : Optimum  rotorcraft  operations Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : This work focuses on the development and application of a generic methodology targeting the design of optimum rotorcraft operations in terms of fuel burn, gaseous emissions, and ground noise impact. An integrated tool capable of estimating the performance and emitted noise of any defined rotorcraft configuration within any designated mission has been deployed. A comprehensive and cost-effective optimization strategy has been structured. The methodology has been applied to two generic, baseline missions representative of current rotorcraft operations. Optimally designed operations for fuel burn, gaseous emissions, and ground noise impact have been obtained. A comparative evaluation has been waged between the acquired optimum designs. The respective trade-off arising from the incorporation of flight paths optimized for different objectives has been quantified. Pareto front derived models for fuel burn and emitted noise have been structured for each mission. The Pareto models have been subsequently deployed for the design of operations optimized in a multidisciplinary manner. The results have shown that the proposed methodology is promising with regards to achieving simultaneous reduction in fuel burn, gaseous emissions, and ground noise impact for any defined mission. The obtainable reductions are found to be dependent on the designated mission. Finally, the potential to design optimum operations in a multidisciplinary fashion using only a single design criterion is demonstrated. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...]

Passive effusion cooling in a rectangular S-bend diffuser / B. C. N. Ng in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 134 N° 9 (Septembre 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 06 p. Titre : Passive effusion cooling in a rectangular S-bend diffuser Type de document : texte imprimé Auteurs : B. C. N. Ng, Auteur ; A. M. Birk, Auteur Année de publication : 2012 Article en page(s) : 06 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Passive  effusion  cooling  S-bend  diffusing  passage  Pressure  probes  Substantial  back-pressure  penalty  Wall  pressure  distribution  alteration  Effusion  holes  locations Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The experimental study considered passive effusion cooling in an S-bend diffusing passage in which ambient cool air was drawn naturally into the S-bend passage with subatmospheric flow distributions. Seven-hole pressure probes were used to measure the test section's inlet and outlet flow conditions which were used to evaluate the performance of the S-bend diffuser. Back-pressure, outlet flow-fields, and wall pressure distributions were investigated to study the effects of effusion cooling on the pressure recovery performance of the S-bend diffuser. The study revealed a substantial back-pressure penalty and wall pressure distribution alteration in the S-bend passage with full coverage effusion cooling. The outlet diffuser was shown to be not as effective with effusion cooling. The findings highlighted the importance of the design of effusion holes locations in complex flow passages. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...] [article] Passive effusion cooling in a rectangular S-bend diffuser [texte imprimé] / B. C. N. Ng, Auteur ; A. M. Birk, Auteur . - 2012 . - 06 p. Génie mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 06 p. Mots-clés : Passive  effusion  cooling  S-bend  diffusing  passage  Pressure  probes  Substantial  back-pressure  penalty  Wall  pressure  distribution  alteration  Effusion  holes  locations Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The experimental study considered passive effusion cooling in an S-bend diffusing passage in which ambient cool air was drawn naturally into the S-bend passage with subatmospheric flow distributions. Seven-hole pressure probes were used to measure the test section's inlet and outlet flow conditions which were used to evaluate the performance of the S-bend diffuser. Back-pressure, outlet flow-fields, and wall pressure distributions were investigated to study the effects of effusion cooling on the pressure recovery performance of the S-bend diffuser. The study revealed a substantial back-pressure penalty and wall pressure distribution alteration in the S-bend passage with full coverage effusion cooling. The outlet diffuser was shown to be not as effective with effusion cooling. The findings highlighted the importance of the design of effusion holes locations in complex flow passages. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...]

The effects of wet compression and blade tip water injection on the stability of a transonic compressor rotor / Luo, Mingcong in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 134 N° 9 (Septembre 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 10 p. Titre : The effects of wet compression and blade tip water injection on the stability of a transonic compressor rotor Type de document : texte imprimé Auteurs : Luo, Mingcong, Auteur ; Zheng, Qun, Auteur ; Sun, Lanxin, Auteur Année de publication : 2012 Article en page(s) : 10 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Compressor  rotor  tip  Tip  injection  Water  injection  Wet  compression Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The rotor blade tip leakage flow and associated formation of the tip leakage vortex and interaction of the tip leakage vortex with the shockwave, particularly in the case of a transonic compressor rotor have significant impact on the compressor performance and its stability. Air injection upstream of the compressor rotor tip has been shown to improve compressor performance and enhance its stability. The air required for rotor blade tip injection is generally taken from the later stages of the compressor thus causing penalty on the gas turbine performance. In this study, effects of water injection at the rotor tip with and without the wet compression on the compressor performance and its stability have been examined. To achieve the stated objectives, the well tested transonic compressor rotor stage, NASA rotor stage 37, has been numerically simulated. The evaluation of results on various performance parameters, such as total pressure ratio, inlet flow capacity, and adiabatic efficiency combined with contours of total pressure losses, entropy, Mach number, and temperature including limiting streamlines, shows that the blade tip water injection could help in reducing low energy region downstream of the shockwave and strength of the tip leakage vortex with the compressor operating at its rotating stall boundary condition. The extent of reduction depends on the droplet size, injection flow rate, and its velocity. Furthermore, results show that combined case of the blade tip water injection and the wet compression could provide better stall margin enhancement than the blade tip water injection case. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...] [article] The effects of wet compression and blade tip water injection on the stability of a transonic compressor rotor [texte imprimé] / Luo, Mingcong, Auteur ; Zheng, Qun, Auteur ; Sun, Lanxin, Auteur . - 2012 . - 10 p. Génie mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 10 p. Mots-clés : Compressor  rotor  tip  Tip  injection  Water  injection  Wet  compression Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The rotor blade tip leakage flow and associated formation of the tip leakage vortex and interaction of the tip leakage vortex with the shockwave, particularly in the case of a transonic compressor rotor have significant impact on the compressor performance and its stability. Air injection upstream of the compressor rotor tip has been shown to improve compressor performance and enhance its stability. The air required for rotor blade tip injection is generally taken from the later stages of the compressor thus causing penalty on the gas turbine performance. In this study, effects of water injection at the rotor tip with and without the wet compression on the compressor performance and its stability have been examined. To achieve the stated objectives, the well tested transonic compressor rotor stage, NASA rotor stage 37, has been numerically simulated. The evaluation of results on various performance parameters, such as total pressure ratio, inlet flow capacity, and adiabatic efficiency combined with contours of total pressure losses, entropy, Mach number, and temperature including limiting streamlines, shows that the blade tip water injection could help in reducing low energy region downstream of the shockwave and strength of the tip leakage vortex with the compressor operating at its rotating stall boundary condition. The extent of reduction depends on the droplet size, injection flow rate, and its velocity. Furthermore, results show that combined case of the blade tip water injection and the wet compression could provide better stall margin enhancement than the blade tip water injection case. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...]

An integrated particle-tracking impact/adhesion model for the prediction of fouling in a subsonic compressor / D. Borello in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 134 N° 9 (Septembre 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 07 p. Titre : An integrated particle-tracking impact/adhesion model for the prediction of fouling in a subsonic compressor Type de document : texte imprimé Auteurs : D. Borello, Auteur ; F. Rispoli, Auteur ; P. Venturini, Auteur Année de publication : 2012 Article en page(s) : 07 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Adhesive  particles  3D  linear  compressor  cascade  Turbomachinery  flows  Hybrid  large-eddy  simulation  (LES)  Reynolds-averaged  Navier-Stokes  (RANS)  computation Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The present paper reports on the analysis of the motion of adhesive particles and deposit formation in a 3D linear compressor cascade in order to investigate the fouling in turbomachinery flows. The unsteady flow field is provided by a prior hybrid large-eddy simulation (LES)/Reynolds-averaged Navier-Stokes (RANS) computation. The particles are individually tracked and the deposit formation is evaluated on the basis of the well-established Thornton and Ning model. Although the study is limited to three regions of the blade, where the most relevant turbulent phenomena occurs, the prediction of fouling shows good agreement with real situations. Deposits form near the casing and the hub, in the zones where there are strong vortical structures originated by the tip leakage and hub vortices. On the blade, the deposit analysis is focused on three main regions: (a) along the stagnation region on the leading edge; (b) on the suction side, where the particles are conveyed by the hub vortex towards blade surfaces; and (c) on the pressure side, where a clean zone forms between leading edge and the blade surface, as can be seen in real compressors. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...] [article] An integrated particle-tracking impact/adhesion model for the prediction of fouling in a subsonic compressor [texte imprimé] / D. Borello, Auteur ; F. Rispoli, Auteur ; P. Venturini, Auteur . - 2012 . - 07 p. Génie mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 07 p. Mots-clés : Adhesive  particles  3D  linear  compressor  cascade  Turbomachinery  flows  Hybrid  large-eddy  simulation  (LES)  Reynolds-averaged  Navier-Stokes  (RANS)  computation Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The present paper reports on the analysis of the motion of adhesive particles and deposit formation in a 3D linear compressor cascade in order to investigate the fouling in turbomachinery flows. The unsteady flow field is provided by a prior hybrid large-eddy simulation (LES)/Reynolds-averaged Navier-Stokes (RANS) computation. The particles are individually tracked and the deposit formation is evaluated on the basis of the well-established Thornton and Ning model. Although the study is limited to three regions of the blade, where the most relevant turbulent phenomena occurs, the prediction of fouling shows good agreement with real situations. Deposits form near the casing and the hub, in the zones where there are strong vortical structures originated by the tip leakage and hub vortices. On the blade, the deposit analysis is focused on three main regions: (a) along the stagnation region on the leading edge; (b) on the suction side, where the particles are conveyed by the hub vortex towards blade surfaces; and (c) on the pressure side, where a clean zone forms between leading edge and the blade surface, as can be seen in real compressors. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...]

Optimal gas-turbine design for hybrid solar power plant operation / James Spelling in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 134 N° 9 (Septembre 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 09 p. Titre : Optimal gas-turbine design for hybrid solar power plant operation Type de document : texte imprimé Auteurs : James Spelling, Auteur ; Björn Laumert, Auteur ; Torsten Fransson, Auteur Année de publication : 2012 Article en page(s) : 09 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Hybrid  solar  gas-turbine  power  plant  Thermodynamic  performance  Economic  performance Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : A dynamic simulation model of a hybrid solar gas-turbine power plant has been developed, allowing determination of its thermodynamic and economic performance. In order to examine optimum gas-turbine designs for hybrid solar power plants, multiobjective thermoeconomic analysis has been performed, with two conflicting objectives: minimum levelized electricity costs and minimum specific CO2 emissions. Optimum cycle conditions: pressure-ratio, receiver temperature, turbine inlet temperature and flow rate, have been identified for a 15 MWe gas-turbine under different degrees of solarization. At moderate solar shares, the hybrid solar gas-turbine concept was shown to provide significant water and CO2 savings with only a minor increase in the levelized electricity cost. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...] [article] Optimal gas-turbine design for hybrid solar power plant operation [texte imprimé] / James Spelling, Auteur ; Björn Laumert, Auteur ; Torsten Fransson, Auteur . - 2012 . - 09 p. Génie mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 09 p. Mots-clés : Hybrid  solar  gas-turbine  power  plant  Thermodynamic  performance  Economic  performance Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : A dynamic simulation model of a hybrid solar gas-turbine power plant has been developed, allowing determination of its thermodynamic and economic performance. In order to examine optimum gas-turbine designs for hybrid solar power plants, multiobjective thermoeconomic analysis has been performed, with two conflicting objectives: minimum levelized electricity costs and minimum specific CO2 emissions. Optimum cycle conditions: pressure-ratio, receiver temperature, turbine inlet temperature and flow rate, have been identified for a 15 MWe gas-turbine under different degrees of solarization. At moderate solar shares, the hybrid solar gas-turbine concept was shown to provide significant water and CO2 savings with only a minor increase in the levelized electricity cost. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...]

Rotor model validation for an active magnetic bearing machining spindle using Mu-synthesis approach / Ryan J. Madden in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 134 N° 9 (Septembre 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 06 p. Titre : Rotor model validation for an active magnetic bearing machining spindle using Mu-synthesis approach Type de document : texte imprimé Auteurs : Ryan J. Madden, Auteur ; Jerzy T. Sawicki, Auteur Année de publication : 2012 Article en page(s) : 06 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Rotor  model  High-speed  machining  spindle  Active  magnetic  bearings  µ-synthesis Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Model-based identification and µ-synthesis are employed for model updating of the rotor for a high-speed machining spindle supported on active magnetic bearings. The experimentally validated model is compared with a nominal engineering model to identify the unmodeled dynamics. The extracted missing dynamics from the nominal rotor model provides engineering insight into an effective model correction strategy. The corrected rotor model is validated by successful implementation of a number of µ-synthesized controllers, providing robust and stable levitation of the spindle over its entire operating speed range. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...] [article] Rotor model validation for an active magnetic bearing machining spindle using Mu-synthesis approach [texte imprimé] / Ryan J. Madden, Auteur ; Jerzy T. Sawicki, Auteur . - 2012 . - 06 p. Génie mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 06 p. Mots-clés : Rotor  model  High-speed  machining  spindle  Active  magnetic  bearings  µ-synthesis Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Model-based identification and µ-synthesis are employed for model updating of the rotor for a high-speed machining spindle supported on active magnetic bearings. The experimentally validated model is compared with a nominal engineering model to identify the unmodeled dynamics. The extracted missing dynamics from the nominal rotor model provides engineering insight into an effective model correction strategy. The corrected rotor model is validated by successful implementation of a number of µ-synthesized controllers, providing robust and stable levitation of the spindle over its entire operating speed range. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...]

Controlled deflection approach for rotor crack detection / Zbigniew Kulesza in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 134 N° 9 (Septembre 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 09 p. Titre : Controlled deflection approach for rotor crack detection Type de document : texte imprimé Auteurs : Zbigniew Kulesza, Auteur ; Jerzy T. Sawicki, Auteur Année de publication : 2012 Article en page(s) : 09 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Transverse  shaft  crack  Rotating  machine Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : A transverse shaft crack is a serious malfunction that can occur due to cyclic loading, creep, stress corrosion, and other mechanisms to which rotating machines are subjected. Though studied for many years, the problems of early crack detection and warning are still in the limelight of many researchers. This is due to the fact that the crack has subtle influence on the dynamic response of the machine and still there are no widely accepted, reliable methods of its early detection. This paper presents a new approach to these problems. The method utilizes the coupling mechanism between the bending and torsional vibrations of the cracked, nonrotating shaft. By applying an external lateral force of constant amplitude, a small shaft deflection is induced. Simultaneously, a harmonic torque is applied to the shaft inducing its torsional vibrations. By changing the angular position of the lateral force application, the position of the deflection also changes opening or closing of the crack. This changes the way the bending and torsional vibrations are being coupled. By studying the coupled lateral vibration response for each angular position of the lateral force one can assess the possible presence of the crack. The approach is demonstrated with a numerical model of a rotor. The model is based on the rigid finite element method (RFE), which has previously been successfully applied for the dynamic analysis of many complicated, mechanical structures. The RFE method is extended and adopted for the modeling of the cracked shafts. An original concept of crack modeling utilizing the RFE method is presented. The crack is modeled as a set of spring-damping elements (SDEs) of variable stiffness connecting two sections of the shaft. By calculating the axial deformations of the SDEs, the opening/closing mechanism of the crack is introduced. The results of numerical analysis demonstrate the potential of the suggested approach for effective shaft crack detection. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...] [article] Controlled deflection approach for rotor crack detection [texte imprimé] / Zbigniew Kulesza, Auteur ; Jerzy T. Sawicki, Auteur . - 2012 . - 09 p. Génie mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 09 p. Mots-clés : Transverse  shaft  crack  Rotating  machine Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : A transverse shaft crack is a serious malfunction that can occur due to cyclic loading, creep, stress corrosion, and other mechanisms to which rotating machines are subjected. Though studied for many years, the problems of early crack detection and warning are still in the limelight of many researchers. This is due to the fact that the crack has subtle influence on the dynamic response of the machine and still there are no widely accepted, reliable methods of its early detection. This paper presents a new approach to these problems. The method utilizes the coupling mechanism between the bending and torsional vibrations of the cracked, nonrotating shaft. By applying an external lateral force of constant amplitude, a small shaft deflection is induced. Simultaneously, a harmonic torque is applied to the shaft inducing its torsional vibrations. By changing the angular position of the lateral force application, the position of the deflection also changes opening or closing of the crack. This changes the way the bending and torsional vibrations are being coupled. By studying the coupled lateral vibration response for each angular position of the lateral force one can assess the possible presence of the crack. The approach is demonstrated with a numerical model of a rotor. The model is based on the rigid finite element method (RFE), which has previously been successfully applied for the dynamic analysis of many complicated, mechanical structures. The RFE method is extended and adopted for the modeling of the cracked shafts. An original concept of crack modeling utilizing the RFE method is presented. The crack is modeled as a set of spring-damping elements (SDEs) of variable stiffness connecting two sections of the shaft. By calculating the axial deformations of the SDEs, the opening/closing mechanism of the crack is introduced. The results of numerical analysis demonstrate the potential of the suggested approach for effective shaft crack detection. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...]

Influence of in-plane dynamics of thin compression rings on friction in internal combustion engines / C. E. Baker in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 134 N° 9 (Septembre 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 11 p. Titre : Influence of in-plane dynamics of thin compression rings on friction in internal combustion engines Type de document : texte imprimé Auteurs : C. E. Baker, Auteur ; S. Theodossiades, Auteur ; H. Rahnejat, Auteur Année de publication : 2012 Article en page(s) : 11 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Thin  compression  rings  Ring  in-plane  modal  dynamics  Mixed  regime  of  lubrication  Salient  features  Internal  combustion  engines  Friction Résumé : The compression ring-bore conjunction accounts for significant frictional parasitic losses relative to its size. The prerequisite to improving the tribological performance of this contact is a fundamental understanding of ring dynamics within the prevailing transient nature of the regime of lubrication. Studies reported thus far take into account ring-bore conformance based on static fitment of the ring within an out-of-round bore, whose out-of-circularity is affected by manufacturing processes, surface treatment, and assembly. The static fitment analyses presume quasi-static equilibrium between ring tension and gas pressure loading with generated conjunctional pressures. This is an implicit assumption of ring rigidity while in situ. The current analysis considers the global modal behavior of the ring as an eigenvalue problem, thus including its dynamic in-plane behavior in the tribological study of a mixed-hydrodynamic regime of lubrication. The results show that the contact transit time is shorter than that required for the ring to reach steady state condition. Hence, the conjunction is not only subject to transience on account of changing contact kinematics and varied combustion loading, but also subject to perpetual ring transient dynamics. This renders the ring-bore friction a more complex problem than usually assumed in idealized ring fitment analyses. An interesting finding of the analysis is increased ring-bore clearance at and in the vicinity of top dead center, which reduces the ring-sealing effect and suggests a possible increase in blow-by. The current analysis, integrating ring in-plane modal dynamics and mixed regime of lubrication, includes salient features, which are a closer representation of practice, an approach which has not hitherto been reported in literature. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...] [article] Influence of in-plane dynamics of thin compression rings on friction in internal combustion engines [texte imprimé] / C. E. Baker, Auteur ; S. Theodossiades, Auteur ; H. Rahnejat, Auteur . - 2012 . - 11 p. Génie mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 11 p. Mots-clés : Thin  compression  rings  Ring  in-plane  modal  dynamics  Mixed  regime  of  lubrication  Salient  features  Internal  combustion  engines  Friction Résumé : The compression ring-bore conjunction accounts for significant frictional parasitic losses relative to its size. The prerequisite to improving the tribological performance of this contact is a fundamental understanding of ring dynamics within the prevailing transient nature of the regime of lubrication. Studies reported thus far take into account ring-bore conformance based on static fitment of the ring within an out-of-round bore, whose out-of-circularity is affected by manufacturing processes, surface treatment, and assembly. The static fitment analyses presume quasi-static equilibrium between ring tension and gas pressure loading with generated conjunctional pressures. This is an implicit assumption of ring rigidity while in situ. The current analysis considers the global modal behavior of the ring as an eigenvalue problem, thus including its dynamic in-plane behavior in the tribological study of a mixed-hydrodynamic regime of lubrication. The results show that the contact transit time is shorter than that required for the ring to reach steady state condition. Hence, the conjunction is not only subject to transience on account of changing contact kinematics and varied combustion loading, but also subject to perpetual ring transient dynamics. This renders the ring-bore friction a more complex problem than usually assumed in idealized ring fitment analyses. An interesting finding of the analysis is increased ring-bore clearance at and in the vicinity of top dead center, which reduces the ring-sealing effect and suggests a possible increase in blow-by. The current analysis, integrating ring in-plane modal dynamics and mixed regime of lubrication, includes salient features, which are a closer representation of practice, an approach which has not hitherto been reported in literature. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...]

Transient behavior of glow plugs in direct-injection natural gas engines / Stewart Xu Cheng in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 134 N° 9 (Septembre 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 08 p. Titre : Transient behavior of glow plugs in direct-injection natural gas engines Type de document : texte imprimé Auteurs : Stewart Xu Cheng, Auteur ; James S. Wallace, Auteur Année de publication : 2012 Article en page(s) : 08 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Glow  plugs  Natural  gas  engines  Direct  injection Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Glow plugs are a possible ignition source for direct injected natural gas engines. This ignition assistance application is much different than the cold start assist function for which most glow plugs have been designed. In the cold start application, the glow plug is simply heating the air in the cylinder. In the cycle-by-cycle ignition assist application, the glow plug needs to achieve high surface temperatures at specific times in the engine cycle to provide a localized source of ignition. Whereas a simple lumped heat capacitance model is a satisfactory representation of the glow plug for the air heating situation, a much more complex situation exists for hot surface ignition. Simple measurements and theoretical analysis show that the thickness of the heat penetration layer is small within the time scale of the ignition preparation period (1–2 ms). The experiments and analysis were used to develop a discretized representation of the glow plug domain. A simplified heat transfer model, incorporating both convection and radiation losses, was developed for the discretized representation to compute heat transfer to and from the surrounding gas. A scheme for coupling the glow plug model to the surrounding gas computational domain in the KIVA-3V engine simulation code was also developed. The glow plug model successfully simulates the natural gas ignition process for a direct-injection natural gas engine. As well, it can provide detailed information on the local glow plug surface temperature distribution, which can aid in the design of more reliable glow plugs. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...] [article] Transient behavior of glow plugs in direct-injection natural gas engines [texte imprimé] / Stewart Xu Cheng, Auteur ; James S. Wallace, Auteur . - 2012 . - 08 p. Génie mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 08 p. Mots-clés : Glow  plugs  Natural  gas  engines  Direct  injection Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Glow plugs are a possible ignition source for direct injected natural gas engines. This ignition assistance application is much different than the cold start assist function for which most glow plugs have been designed. In the cold start application, the glow plug is simply heating the air in the cylinder. In the cycle-by-cycle ignition assist application, the glow plug needs to achieve high surface temperatures at specific times in the engine cycle to provide a localized source of ignition. Whereas a simple lumped heat capacitance model is a satisfactory representation of the glow plug for the air heating situation, a much more complex situation exists for hot surface ignition. Simple measurements and theoretical analysis show that the thickness of the heat penetration layer is small within the time scale of the ignition preparation period (1–2 ms). The experiments and analysis were used to develop a discretized representation of the glow plug domain. A simplified heat transfer model, incorporating both convection and radiation losses, was developed for the discretized representation to compute heat transfer to and from the surrounding gas. A scheme for coupling the glow plug model to the surrounding gas computational domain in the KIVA-3V engine simulation code was also developed. The glow plug model successfully simulates the natural gas ignition process for a direct-injection natural gas engine. As well, it can provide detailed information on the local glow plug surface temperature distribution, which can aid in the design of more reliable glow plugs. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...]

Soot evolution with cyclic crank-angle-resolved two-color thermometry in an optical diesel engine fueled with biodiesel blend and ULSD / Kan Zha in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 134 N° 9 (Septembre 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 07 p. Titre : Soot evolution with cyclic crank-angle-resolved two-color thermometry in an optical diesel engine fueled with biodiesel blend and ULSD Type de document : texte imprimé Auteurs : Kan Zha, Auteur ; Radu-Catalin Florea, Auteur ; Marcis Jansons, Auteur Année de publication : 2012 Article en page(s) : 07 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Biodiesel  Soot  emission  Petroleum-based  diesel  fuels Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Biodiesel is a desirable alternative fuel for the diesel engine due to its low engine-out soot emission tendency. When blended with petroleum-based diesel fuels, soot emissions generally decrease in proportion to the volume fraction of biodiesel in the mixture. While comparisons of engine-out soot measurements between biodiesel blends and petroleum-based diesel have been widely reported, in-cylinder soot evolution has not been experimentally explored to the same extent. To elucidate the soot emission reduction mechanism of biodiesel, a single-cylinder optically-accessible diesel engine was used to compare the in-cylinder soot evolution when fueled with ultra-low sulfur diesel (ULSD) to that using a B20 biodiesel blend (20% vol./vol. biodiesel ASTM D6751-03A). Soot temperature and KL factors are simultaneously determined using a novel two-color optical thermometry technique implemented with a high-speed CMOS color camera having wide-band Bayer filters. The crank-angle resolved data allows quantitative comparison of the rate of in-cylinder soot formation. High-speed spray images show that B20 has more splashing during spray wall impingement than ULSD, distributing rebounding fuel droplets over a thicker annular ring interior to the piston bowl periphery. The subsequent soot luminescence is observed by high-speed combustion imaging and soot temperature and KL factor measurements. B20 forms soot both at low KL magnitudes over large areas between fuel jets, and at high values among remnants of the fuel spray, along its axis and away from the bowl edge. In contrast, ULSD soot luminescence is observed exclusively as pool burning on the piston bowl surfaces resulting from spray wall impingement. The soot KL factor evolution during B20 combustion indicates earlier and significantly greater soot formation than with ULSD. B20 combustion is also observed to have a greater soot oxidation rate, which results in lower late-cycle soot emissions. For both fuels, higher fuel injection pressure led to lower late-cycle soot KL levels. The apparent rate of heat release (ARHR) analysis under steady skip-fire conditions indicates that B20 combustion is less sensitive to wall temperature than that observed with ULSD due to a lesser degree of pool burning. B20 was found to have both a shorter ignition delay and shorter combustion duration than ULSD. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...] [article] Soot evolution with cyclic crank-angle-resolved two-color thermometry in an optical diesel engine fueled with biodiesel blend and ULSD [texte imprimé] / Kan Zha, Auteur ; Radu-Catalin Florea, Auteur ; Marcis Jansons, Auteur . - 2012 . - 07 p. Génie mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 07 p. Mots-clés : Biodiesel  Soot  emission  Petroleum-based  diesel  fuels Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Biodiesel is a desirable alternative fuel for the diesel engine due to its low engine-out soot emission tendency. When blended with petroleum-based diesel fuels, soot emissions generally decrease in proportion to the volume fraction of biodiesel in the mixture. While comparisons of engine-out soot measurements between biodiesel blends and petroleum-based diesel have been widely reported, in-cylinder soot evolution has not been experimentally explored to the same extent. To elucidate the soot emission reduction mechanism of biodiesel, a single-cylinder optically-accessible diesel engine was used to compare the in-cylinder soot evolution when fueled with ultra-low sulfur diesel (ULSD) to that using a B20 biodiesel blend (20% vol./vol. biodiesel ASTM D6751-03A). Soot temperature and KL factors are simultaneously determined using a novel two-color optical thermometry technique implemented with a high-speed CMOS color camera having wide-band Bayer filters. The crank-angle resolved data allows quantitative comparison of the rate of in-cylinder soot formation. High-speed spray images show that B20 has more splashing during spray wall impingement than ULSD, distributing rebounding fuel droplets over a thicker annular ring interior to the piston bowl periphery. The subsequent soot luminescence is observed by high-speed combustion imaging and soot temperature and KL factor measurements. B20 forms soot both at low KL magnitudes over large areas between fuel jets, and at high values among remnants of the fuel spray, along its axis and away from the bowl edge. In contrast, ULSD soot luminescence is observed exclusively as pool burning on the piston bowl surfaces resulting from spray wall impingement. The soot KL factor evolution during B20 combustion indicates earlier and significantly greater soot formation than with ULSD. B20 combustion is also observed to have a greater soot oxidation rate, which results in lower late-cycle soot emissions. For both fuels, higher fuel injection pressure led to lower late-cycle soot KL levels. The apparent rate of heat release (ARHR) analysis under steady skip-fire conditions indicates that B20 combustion is less sensitive to wall temperature than that observed with ULSD due to a lesser degree of pool burning. B20 was found to have both a shorter ignition delay and shorter combustion duration than ULSD. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...]

The effect of intake valve deactivation on lean stratified charge combustion at an idling condition of a spark ignition direct injection engine / Ronald O. Grover, Jr. in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 134 N° 9 (Septembre 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 11 p. Titre : The effect of intake valve deactivation on lean stratified charge combustion at an idling condition of a spark ignition direct injection engine Type de document : texte imprimé Auteurs : Ronald O. Grover, Jr., Auteur ; Junseok Chang, Auteur ; Edward R. Masters, Auteur Année de publication : 2012 Article en page(s) : 11 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Intake  valve  deactivation  Spark  ignition  direct  injection  (SIDI)  Computational  fluid  dynamics  (CFD) Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : A combined experimental and analytical study was carried out to understand the improvement in combustion performance of a four-valve spark ignition direct injection (SIDI) wall-guided engine operating at lean, stratified idle with enhanced in-cylinder charge motion by deactivating one of the two intake valves. A fully warmed-up engine was operated at low speed, light load by injecting the fuel from a pressure-swirl injector during the compression stroke to produce a stratified fuel cloud surrounding the spark plug at the time of ignition. Steady state flow-bench measurements and computational fluid dynamics (CFD) calculations showed that valve deactivation primarily increased the in-cylinder swirl intensity as compared with opening both intake valves. Engine dynamometer measurements showed an increase in charge motion led to improved combustion stability, increased combustion efficiency, lower fuel consumption, and higher dilution tolerance. A CFD study was conducted using in-house models of spray and combustion to simulate the engine operating with and without valve deactivation. The computations demonstrated that the improved combustion was primarily driven by higher laminar flame speeds through enhanced mixing of internal residual gases, better containment of the fuel cloud within the piston bowl, and higher postflame diffusion burn rates during the initial, main, and late stages of the combustion process, respectively. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...] [article] The effect of intake valve deactivation on lean stratified charge combustion at an idling condition of a spark ignition direct injection engine [texte imprimé] / Ronald O. Grover, Jr., Auteur ; Junseok Chang, Auteur ; Edward R. Masters, Auteur . - 2012 . - 11 p. Génie mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 11 p. Mots-clés : Intake  valve  deactivation  Spark  ignition  direct  injection  (SIDI)  Computational  fluid  dynamics  (CFD) Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : A combined experimental and analytical study was carried out to understand the improvement in combustion performance of a four-valve spark ignition direct injection (SIDI) wall-guided engine operating at lean, stratified idle with enhanced in-cylinder charge motion by deactivating one of the two intake valves. A fully warmed-up engine was operated at low speed, light load by injecting the fuel from a pressure-swirl injector during the compression stroke to produce a stratified fuel cloud surrounding the spark plug at the time of ignition. Steady state flow-bench measurements and computational fluid dynamics (CFD) calculations showed that valve deactivation primarily increased the in-cylinder swirl intensity as compared with opening both intake valves. Engine dynamometer measurements showed an increase in charge motion led to improved combustion stability, increased combustion efficiency, lower fuel consumption, and higher dilution tolerance. A CFD study was conducted using in-house models of spray and combustion to simulate the engine operating with and without valve deactivation. The computations demonstrated that the improved combustion was primarily driven by higher laminar flame speeds through enhanced mixing of internal residual gases, better containment of the fuel cloud within the piston bowl, and higher postflame diffusion burn rates during the initial, main, and late stages of the combustion process, respectively. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...]

Oxidative stability of algae derived methyl esters / Harrison Bucy in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 134 N° 9 (Septembre 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 13 p. Titre : Oxidative stability of algae derived methyl esters Type de document : texte imprimé Auteurs : Harrison Bucy, Auteur ; Anthony J. Marchese, Auteur Année de publication : 2012 Article en page(s) : 13 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Microalgae  Biofuel  feedstock  Algal  methyl  ester  biodiesel Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Microalgae are currently receiving strong consideration as a potential biofuel feedstock to help meet the advanced biofuels mandate of the 2007 Energy Independence and Security Act because of its theoretically high yield (gal/acre/year) in comparison to current terrestrial feedstocks. For algal methyl ester biodiesel, fuel properties will be directly related to the fatty acid composition of the lipids produced by the given microalgae strain. Several microalgae species under consideration for wide scale cultivation, such as Nannochloropsis, produce lipids with fatty acid compositions containing substantially higher quantities of long chain-polyunsaturated fatty acids (LC-PUFA) in comparison to terrestrial feedstocks. It is expected that increased levels of LC-PUFA will be problematic in terms of meeting all of the current ASTM specifications for biodiesel. Moreover, these same LC-PUFA fatty acids, such as eicosapentaenoic acid (EPA: C20:5) and docosahexaenoic acid (DHA: C22:6) are known to have high nutritional value, thereby making separation of these compounds economically attractive. Given the uncertainty in the future value of these LC-PUFA compounds and the economic viability of the separation process, the goal of this study was to examine the oxidative stability of algal methyl esters with varying levels of EPA and DHA. Tests were conducted using a Metrohm 743 Rancimat with automatic induction period determination following ASTM D6751 and EN 14214 standards, which call for induction periods of at least 3 and 6 h, respectively. Tests were conducted at a temperature of 110 °C and airflow of 10 l/h with model algal methyl ester compounds synthesized from various sources to match the fatty acid compositions of several algae strains subjected to varying removal amounts of roughly 0% to 100% LC-PUFA. In addition, tests were also conducted with real algal methyl esters produced from multiple sources. The bis-allylic position equivalent (BAPE) was calculated for each fuel sample to quantify the level of unsaturation. The induction period was then plotted as a function of BAPE, which showed that the oxidative stability varied exponentially with the amount of LC-PUFA. The results suggest that removal of 45% to 65% of the LC-PUFA from Nannochloropsis-based algal methyl esters would be sufficient for meeting existing ASTM specifications for oxidative stability. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...] [article] Oxidative stability of algae derived methyl esters [texte imprimé] / Harrison Bucy, Auteur ; Anthony J. Marchese, Auteur . - 2012 . - 13 p. Génie mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 13 p. Mots-clés : Microalgae  Biofuel  feedstock  Algal  methyl  ester  biodiesel Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Microalgae are currently receiving strong consideration as a potential biofuel feedstock to help meet the advanced biofuels mandate of the 2007 Energy Independence and Security Act because of its theoretically high yield (gal/acre/year) in comparison to current terrestrial feedstocks. For algal methyl ester biodiesel, fuel properties will be directly related to the fatty acid composition of the lipids produced by the given microalgae strain. Several microalgae species under consideration for wide scale cultivation, such as Nannochloropsis, produce lipids with fatty acid compositions containing substantially higher quantities of long chain-polyunsaturated fatty acids (LC-PUFA) in comparison to terrestrial feedstocks. It is expected that increased levels of LC-PUFA will be problematic in terms of meeting all of the current ASTM specifications for biodiesel. Moreover, these same LC-PUFA fatty acids, such as eicosapentaenoic acid (EPA: C20:5) and docosahexaenoic acid (DHA: C22:6) are known to have high nutritional value, thereby making separation of these compounds economically attractive. Given the uncertainty in the future value of these LC-PUFA compounds and the economic viability of the separation process, the goal of this study was to examine the oxidative stability of algal methyl esters with varying levels of EPA and DHA. Tests were conducted using a Metrohm 743 Rancimat with automatic induction period determination following ASTM D6751 and EN 14214 standards, which call for induction periods of at least 3 and 6 h, respectively. Tests were conducted at a temperature of 110 °C and airflow of 10 l/h with model algal methyl ester compounds synthesized from various sources to match the fatty acid compositions of several algae strains subjected to varying removal amounts of roughly 0% to 100% LC-PUFA. In addition, tests were also conducted with real algal methyl esters produced from multiple sources. The bis-allylic position equivalent (BAPE) was calculated for each fuel sample to quantify the level of unsaturation. The induction period was then plotted as a function of BAPE, which showed that the oxidative stability varied exponentially with the amount of LC-PUFA. The results suggest that removal of 45% to 65% of the LC-PUFA from Nannochloropsis-based algal methyl esters would be sufficient for meeting existing ASTM specifications for oxidative stability. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...]

Real-time transient soot and NOx virtual sensors for diesel engine using neuro-fuzzy model tree and orthogonal least squares / Rajit Johri in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 134 N° 9 (Septembre 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 09 p. Titre : Real-time transient soot and NOx virtual sensors for diesel engine using neuro-fuzzy model tree and orthogonal least squares Type de document : texte imprimé Auteurs : Rajit Johri, Auteur ; Ashwin Salvi, Auteur ; Zoran Filipi, Auteur Année de publication : 2012 Article en page(s) : 09 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Diesel  engine  combustion  Engine  exhaust  emission  Neuro-fuzzy  model  tree  NOx  virtual  sensors Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Diesel engine combustion and emission formation is highly nonlinear and thus creates a challenge related to engine diagnostics and engine control with emission feedback. This paper presents a novel methodology to address the challenge and develop virtual sensing models for engine exhaust emission. These models are capable of predicting transient emissions accurately and are computationally efficient for control and optimization studies. The emission models developed in this paper belong to the family of hierarchical models, namely the “neuro-fuzzy model tree.” The approach is based on divide-and-conquer strategy, i.e., to divide a complex problem into multiple simpler subproblems, which can then be identified using a simpler class of models. Advanced experimental setup incorporating a medium duty diesel engine is used to generate training data. Fast emission analyzers for soot and NOx provide instantaneous engine-out emissions. Finally, the engine-in-the-loop is used to validate the models for predicting transient particulate mass and NOx. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...] [article] Real-time transient soot and NOx virtual sensors for diesel engine using neuro-fuzzy model tree and orthogonal least squares [texte imprimé] / Rajit Johri, Auteur ; Ashwin Salvi, Auteur ; Zoran Filipi, Auteur . - 2012 . - 09 p. Génie mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 09 p. Mots-clés : Diesel  engine  combustion  Engine  exhaust  emission  Neuro-fuzzy  model  tree  NOx  virtual  sensors Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Diesel engine combustion and emission formation is highly nonlinear and thus creates a challenge related to engine diagnostics and engine control with emission feedback. This paper presents a novel methodology to address the challenge and develop virtual sensing models for engine exhaust emission. These models are capable of predicting transient emissions accurately and are computationally efficient for control and optimization studies. The emission models developed in this paper belong to the family of hierarchical models, namely the “neuro-fuzzy model tree.” The approach is based on divide-and-conquer strategy, i.e., to divide a complex problem into multiple simpler subproblems, which can then be identified using a simpler class of models. Advanced experimental setup incorporating a medium duty diesel engine is used to generate training data. Fast emission analyzers for soot and NOx provide instantaneous engine-out emissions. Finally, the engine-in-the-loop is used to validate the models for predicting transient particulate mass and NOx. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...]

Particle number emissions of nonroad diesel engines of various ages / Seppo Niemi in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 134 N° 9 (Septembre 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 11 p. Titre : Particle number emissions of nonroad diesel engines of various ages Type de document : texte imprimé Auteurs : Seppo Niemi, Auteur ; Krister Ekman, Auteur ; Pekka Nousiainen, Auteur Année de publication : 2012 Article en page(s) : 11 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Diesel  engines  Gaseous  emission  Particle  mass  emissions  Combustion Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Over the last two decades, gaseous and particle mass emissions of new diesel engines have been reduced effectively and progressively in response to the emissions legislation and due to the applied new technologies. There is, however, increasing concern about whether the engine modifications, while improving combustion and reducing emissions, have increased the number emissions of ultrafine and nanoparticles. So far, emissions regulations have solely been based on particulate matter (PM) mass measurements, not on particle number. Nanoparticles, however, form a major part of the PM emissions, but they do not considerably contribute to the PM mass and cannot be seen as a problem, if only PM mass is determined. Therefore, there is increasing interest in expanding the scope of the regulations to also include particle number emissions, e.g., Euro VI for on-road engines. The PM number limit will also be enforced for nonroad engines slightly later. Thus, more information is required about the particle number emissions themselves, but also about the effects of the engine technology on them. Wall-flow diesel particulate filters reduce the particle number very effectively within the entire particle size range. Nevertheless, in order to keep the filter as small as possible and to lessen the need for regeneration, the engine-out PM number should also be minimized. If the diesel particulate filters (DPFs) could be left out or replaced by a simpler filter, there would be greater freedom of space utilization or cost savings in many nonroad applications. This might be realized in installations where the engine is tuned at high raw NOx and a selective catalytic reduction (SCR) system is adopted for NOx reduction. However, it is not self-evident that new engine technologies would reduce the PM number emissions sufficiently. In this study, particle number emissions were analyzed in several nonroad diesel engines, representing different engine generations and exploiting different emissions reduction technologies: four- or two-valve heads, exhaust gas recirculation, different injection pressures and strategies, etc. All engines were turbocharged, intercooled, direct-injection nonroad diesel engines. Most engines used common-rail fuel injection technology. Comparisons were, however, also performed with engines utilizing either a distributor-type or an in-line fuel injection pump to see the long-term development of the particle number emissions. In this paper, the PM number emissions of nine nonroad diesel engines are presented and compared. Gaseous exhaust emissions and fuel consumption figures are also provided DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...] [article] Particle number emissions of nonroad diesel engines of various ages [texte imprimé] / Seppo Niemi, Auteur ; Krister Ekman, Auteur ; Pekka Nousiainen, Auteur . - 2012 . - 11 p. Génie mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 11 p. Mots-clés : Diesel  engines  Gaseous  emission  Particle  mass  emissions  Combustion Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Over the last two decades, gaseous and particle mass emissions of new diesel engines have been reduced effectively and progressively in response to the emissions legislation and due to the applied new technologies. There is, however, increasing concern about whether the engine modifications, while improving combustion and reducing emissions, have increased the number emissions of ultrafine and nanoparticles. So far, emissions regulations have solely been based on particulate matter (PM) mass measurements, not on particle number. Nanoparticles, however, form a major part of the PM emissions, but they do not considerably contribute to the PM mass and cannot be seen as a problem, if only PM mass is determined. Therefore, there is increasing interest in expanding the scope of the regulations to also include particle number emissions, e.g., Euro VI for on-road engines. The PM number limit will also be enforced for nonroad engines slightly later. Thus, more information is required about the particle number emissions themselves, but also about the effects of the engine technology on them. Wall-flow diesel particulate filters reduce the particle number very effectively within the entire particle size range. Nevertheless, in order to keep the filter as small as possible and to lessen the need for regeneration, the engine-out PM number should also be minimized. If the diesel particulate filters (DPFs) could be left out or replaced by a simpler filter, there would be greater freedom of space utilization or cost savings in many nonroad applications. This might be realized in installations where the engine is tuned at high raw NOx and a selective catalytic reduction (SCR) system is adopted for NOx reduction. However, it is not self-evident that new engine technologies would reduce the PM number emissions sufficiently. In this study, particle number emissions were analyzed in several nonroad diesel engines, representing different engine generations and exploiting different emissions reduction technologies: four- or two-valve heads, exhaust gas recirculation, different injection pressures and strategies, etc. All engines were turbocharged, intercooled, direct-injection nonroad diesel engines. Most engines used common-rail fuel injection technology. Comparisons were, however, also performed with engines utilizing either a distributor-type or an in-line fuel injection pump to see the long-term development of the particle number emissions. In this paper, the PM number emissions of nine nonroad diesel engines are presented and compared. Gaseous exhaust emissions and fuel consumption figures are also provided DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...]

End-of-injection behavior of diesel sprays measured with X-ray radiography / Alan Kastengren in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 134 N° 9 (Septembre 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 04 p. Titre : End-of-injection behavior of diesel sprays measured with X-ray radiography Type de document : texte imprimé Auteurs : Alan Kastengren, Auteur ; Christopher F. Powell, Auteur ; F. Zak Tilocco, Auteur Année de publication : 2012 Article en page(s) : 04 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Diesel  fuel  sprays  Diesel  engine  emissions  X-ray  radiography Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The behavior of diesel fuel sprays at the end of injection is poorly understood, yet has important implications regarding diesel engine emissions. Recent research has shown that at the end of injection, an entrainment wave is created, causing the fuel spray to rapidly entrain ambient gas. This rapid entrainment creates a dilute mixture of fuel that may be a source of unburned fuel emissions. In this study, X-ray radiography is used to quantitatively probe the fuel mass distribution in diesel sprays at the end of injection. Analysis of the spray velocity at steady-state suggests an entrainment wave speed of several hundred m/s, which is supported by the appearance of a traveling entrainment wave at low ambient density. The spray density declines most rapidly near the nozzle, a behavior that matches the expected entrainment wave behavior. The dilution of the spray plume is most prominent in the central dense region of the spray. Three-dimensional reconstructions of the spray density at the end of injection show that the spray plume considerably widens, enhancing the dilution caused by the reduction in fuel flow. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...] [article] End-of-injection behavior of diesel sprays measured with X-ray radiography [texte imprimé] / Alan Kastengren, Auteur ; Christopher F. Powell, Auteur ; F. Zak Tilocco, Auteur . - 2012 . - 04 p. Génie mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 04 p. Mots-clés : Diesel  fuel  sprays  Diesel  engine  emissions  X-ray  radiography Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The behavior of diesel fuel sprays at the end of injection is poorly understood, yet has important implications regarding diesel engine emissions. Recent research has shown that at the end of injection, an entrainment wave is created, causing the fuel spray to rapidly entrain ambient gas. This rapid entrainment creates a dilute mixture of fuel that may be a source of unburned fuel emissions. In this study, X-ray radiography is used to quantitatively probe the fuel mass distribution in diesel sprays at the end of injection. Analysis of the spray velocity at steady-state suggests an entrainment wave speed of several hundred m/s, which is supported by the appearance of a traveling entrainment wave at low ambient density. The spray density declines most rapidly near the nozzle, a behavior that matches the expected entrainment wave behavior. The dilution of the spray plume is most prominent in the central dense region of the spray. Three-dimensional reconstructions of the spray density at the end of injection show that the spray plume considerably widens, enhancing the dilution caused by the reduction in fuel flow. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...]

Nonlinear control of aircraft engines using a generalized gronwall-bellman lemma approach / Jiqiang Wang in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 134 N° 9 (Septembre 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 06 p. Titre : Nonlinear control of aircraft engines using a generalized gronwall-bellman lemma approach Type de document : texte imprimé Auteurs : Jiqiang Wang, Auteur ; Zhifeng Ye, Auteur ; Zhongzhi Hu, Auteur Année de publication : 2012 Article en page(s) : 06 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Aircraft  engine  control  Nonlinear  process  model  Generalized  Gronwall-Bellman  lemma Résumé : Model-based design has attracted much attention in the field of aircraft engine control in recent years. As an aircraft engine is a complicated thermomechanical system, it can only be represented by a nonlinear process model. This necessitates the study of the nonlinear control techniques. Based on our recent results, this paper proposes a novel design approach based on a generalized Gronwall-Bellman lemma. Important results are obtained on bounding behavior of the nonlinear states of the engine. The proposed method is easy to design and tune with the appealing feature of enlarging the feasible control envelope. Finally, a simulation study is provided to validate the effectiveness of the control design approach. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...] [article] Nonlinear control of aircraft engines using a generalized gronwall-bellman lemma approach [texte imprimé] / Jiqiang Wang, Auteur ; Zhifeng Ye, Auteur ; Zhongzhi Hu, Auteur . - 2012 . - 06 p. Génie mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 06 p. Mots-clés : Aircraft  engine  control  Nonlinear  process  model  Generalized  Gronwall-Bellman  lemma Résumé : Model-based design has attracted much attention in the field of aircraft engine control in recent years. As an aircraft engine is a complicated thermomechanical system, it can only be represented by a nonlinear process model. This necessitates the study of the nonlinear control techniques. Based on our recent results, this paper proposes a novel design approach based on a generalized Gronwall-Bellman lemma. Important results are obtained on bounding behavior of the nonlinear states of the engine. The proposed method is easy to design and tune with the appealing feature of enlarging the feasible control envelope. Finally, a simulation study is provided to validate the effectiveness of the control design approach. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...]

Prediction of axial and circumferential flow conditions in a high temperature foil bearing with axial cooling flow / Ryu, Keun in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 134 N° 9 (Septembre 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 06 p. Titre : Prediction of axial and circumferential flow conditions in a high temperature foil bearing with axial cooling flow Type de document : texte imprimé Auteurs : Ryu, Keun, Auteur Année de publication : 2012 Article en page(s) : 06 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Gas  foil  bearings  (GFBs)  Thermal  management  GFB-rotor  system  Axial  cooling  streams Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : A successful implementation of gas foil bearings (GFBs) into high temperature turbomachinery requires adequate thermal management to maintain system reliability and stability. The most common approach for thermal management in a GFB-rotor system is to supply pressurized air at one end of the bearing to remove hot spots in the bearings and control thermal growth of components. This technical brief presents test data for a laboratory rotor-GFB system operating hot to identify the flow characteristics of axial cooling streams flowing through the thin film region and underneath the top foil. A bulk flow model is used for description of the fluid motion and includes the Hirs' friction factor formulation for smooth surfaces. Laminar flow prevails through the thin film gas region; while for the cooling flow between the top foil and bearing housing, a transition from laminar flow to turbulent flow occurs as the cooling flow rate increases. Large cooling flow rate and the ensuing turbulent flow conditions render limited effectiveness in controlling temperatures in a test rotor-GFB system. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...] [article] Prediction of axial and circumferential flow conditions in a high temperature foil bearing with axial cooling flow [texte imprimé] / Ryu, Keun, Auteur . - 2012 . - 06 p. Génie mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 9 (Septembre 2012) . - 06 p. Mots-clés : Gas  foil  bearings  (GFBs)  Thermal  management  GFB-rotor  system  Axial  cooling  streams Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : A successful implementation of gas foil bearings (GFBs) into high temperature turbomachinery requires adequate thermal management to maintain system reliability and stability. The most common approach for thermal management in a GFB-rotor system is to supply pressurized air at one end of the bearing to remove hot spots in the bearings and control thermal growth of components. This technical brief presents test data for a laboratory rotor-GFB system operating hot to identify the flow characteristics of axial cooling streams flowing through the thin film region and underneath the top foil. A bulk flow model is used for description of the fluid motion and includes the Hirs' friction factor formulation for smooth surfaces. Laminar flow prevails through the thin film gas region; while for the cooling flow between the top foil and bearing housing, a transition from laminar flow to turbulent flow occurs as the cooling flow rate increases. Large cooling flow rate and the ensuing turbulent flow conditions render limited effectiveness in controlling temperatures in a test rotor-GFB system. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000009 [...]

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