A. Torregrosa, Alberto Broatch Jacobi, Jorge García-Tíscar, Marc Rodríguez Pastor
Lean Direct Injection (LDI) burners are a promising technology aimed at reducing NOx emissions in new generation aeroengines. However, one of the main drawbacks of this technology is the appearance of combustion instabilities at certain operating conditions. In order to investigate these issues, a confined, atmospheric, swirl-stabilized LDI burner has been set up at the Institute CMT-Motores Térmicos. In this configuration, air mass flow, temperature, and fuel mass flow rate, which is controlled by the injection pressure, can be independently modified to reach different combustion states. In this paper, a parametric study of the equivalence ratio (0.3 ≤ Φ ≤ 0.8), air temperature (50, 100, 150 °C) and fuel mass flow rate (200, 250, 300, 335, 370 mg/s) has been performed to assess their influence on the dynamics of the system through the evaluation of the pressure signals inside the chamber. These signals have been acquired with two piezoresistive sensors flush-mounted to the combustor wall at the same axial distance but in opposite sides of the chamber. Large-amplitude unsteady oscillations are detected for some combinations of the variables of interest. Equivalence ratio variations are shown to affect deeply the dynamic features of the pressure signal, obtaining more stable configurations either close to the lean limit (Φ = 0.3) or at the richest condition tested (Φ = 0.8). Mid-range equivalence ratio values (0.4 ≤ Φ ≤ 0.7) are shown to display the most unstable behavior, featuring large pressure oscillations that remain nearly constant over time (quasi-periodic states) or signals that experience sudden variations in their amplitude (intermittent states). Since turbulent swirl-stabilized spray flame combustors may experience complex flow-flame interactions that could lead to nonlinear behavior of these combustion regimes, several signal processing techniques such as three-dimensional phase space reconstruction or recurrence plots have been applied to the experimental data in order to obtain better insight into these highly dynamic features.
{"title":"Nonlinear Dynamic Analysis of the Pressure Signals on a Swirl-Stabilized Atmospheric LDI Burner Across Different Operating Conditions","authors":"A. Torregrosa, Alberto Broatch Jacobi, Jorge García-Tíscar, Marc Rodríguez Pastor","doi":"10.1115/gt2022-82665","DOIUrl":"https://doi.org/10.1115/gt2022-82665","url":null,"abstract":"Lean Direct Injection (LDI) burners are a promising technology aimed at reducing NOx emissions in new generation aeroengines. However, one of the main drawbacks of this technology is the appearance of combustion instabilities at certain operating conditions. In order to investigate these issues, a confined, atmospheric, swirl-stabilized LDI burner has been set up at the Institute CMT-Motores Térmicos. In this configuration, air mass flow, temperature, and fuel mass flow rate, which is controlled by the injection pressure, can be independently modified to reach different combustion states. In this paper, a parametric study of the equivalence ratio (0.3 ≤ Φ ≤ 0.8), air temperature (50, 100, 150 °C) and fuel mass flow rate (200, 250, 300, 335, 370 mg/s) has been performed to assess their influence on the dynamics of the system through the evaluation of the pressure signals inside the chamber. These signals have been acquired with two piezoresistive sensors flush-mounted to the combustor wall at the same axial distance but in opposite sides of the chamber. Large-amplitude unsteady oscillations are detected for some combinations of the variables of interest. Equivalence ratio variations are shown to affect deeply the dynamic features of the pressure signal, obtaining more stable configurations either close to the lean limit (Φ = 0.3) or at the richest condition tested (Φ = 0.8). Mid-range equivalence ratio values (0.4 ≤ Φ ≤ 0.7) are shown to display the most unstable behavior, featuring large pressure oscillations that remain nearly constant over time (quasi-periodic states) or signals that experience sudden variations in their amplitude (intermittent states). Since turbulent swirl-stabilized spray flame combustors may experience complex flow-flame interactions that could lead to nonlinear behavior of these combustion regimes, several signal processing techniques such as three-dimensional phase space reconstruction or recurrence plots have been applied to the experimental data in order to obtain better insight into these highly dynamic features.","PeriodicalId":395231,"journal":{"name":"Volume 3B: Combustion, Fuels, and Emissions","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130897917","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Puggelli, J. Leparoux, Clément Brunet, R. Mercier, Luce Liberatori, S. Zurbach, G. Cabot, F. Grisch
Lean combustion is an attractive alternative to limit pollutants levels in order to meet the imposed limitations for the next generation of civil aero-engines. However, its implementation involves important technological questions related to the augmentation of the air dedicated to the combustion process. An effort on the injection system design is required and Large Eddy Simulation (LES) can be a useful tool in order to explore the design of novel concepts. At the state of the art, the validation of LES in high-pressure reactive conditions and in presence of the liquid phase is still limited. This shrinks the understanding and optimization of lean devices. The industrial project PERCEVAL, between Safran Tech and the CORIA laboratory, aims at extending the actual knowhow on lean combustion. Novel optical experimental techniques have been developed at CORIA to gain detailed information on industrial injection systems at high-pressure conditions. Within PERCEVAL, Safran Tech is in charge of the assessment of LES by using the experimental data-set collected at CORIA. In this framework, a novel Automatic Mesh Convergence (AMC) procedure, based on adaptive mesh refinement, has been developed in the YALES2 platform to speedup the calculation process. In the present paper, the AMC framework is described and then applied on the lean injection system designed at Safran Tech and tested during PERCEVAL. An analysis is carried out to evaluate the interest and gains offered by the AMC framework.
{"title":"Application of an Automatic Mesh Convergence Procedure for the Large Eddy Simulation of a Multipoint Injection System","authors":"S. Puggelli, J. Leparoux, Clément Brunet, R. Mercier, Luce Liberatori, S. Zurbach, G. Cabot, F. Grisch","doi":"10.1115/gt2022-82272","DOIUrl":"https://doi.org/10.1115/gt2022-82272","url":null,"abstract":"\u0000 Lean combustion is an attractive alternative to limit pollutants levels in order to meet the imposed limitations for the next generation of civil aero-engines. However, its implementation involves important technological questions related to the augmentation of the air dedicated to the combustion process. An effort on the injection system design is required and Large Eddy Simulation (LES) can be a useful tool in order to explore the design of novel concepts. At the state of the art, the validation of LES in high-pressure reactive conditions and in presence of the liquid phase is still limited. This shrinks the understanding and optimization of lean devices. The industrial project PERCEVAL, between Safran Tech and the CORIA laboratory, aims at extending the actual knowhow on lean combustion. Novel optical experimental techniques have been developed at CORIA to gain detailed information on industrial injection systems at high-pressure conditions. Within PERCEVAL, Safran Tech is in charge of the assessment of LES by using the experimental data-set collected at CORIA. In this framework, a novel Automatic Mesh Convergence (AMC) procedure, based on adaptive mesh refinement, has been developed in the YALES2 platform to speedup the calculation process. In the present paper, the AMC framework is described and then applied on the lean injection system designed at Safran Tech and tested during PERCEVAL. An analysis is carried out to evaluate the interest and gains offered by the AMC framework.","PeriodicalId":395231,"journal":{"name":"Volume 3B: Combustion, Fuels, and Emissions","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129690027","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Modern combustors operate with lean mixtures to prevent Nitrogen oxides (NOx) formation by limiting the peaks of the temperature inside the combustion chamber. One of the main drawbacks of these technologies is the higher risk of Lean Blow-Off (LBO) compared to the state-of-art Rich Quench Lean combustors. To limit this possibility, combustor designers introduced pioneering concepts for this component. In this fashion, the CHAiRLIFT (Compact Helical Arranged combustoRs with lean LIFTed flames) concept founds its advantages in the structure of the combustion chamber. It combines two concepts: the tilting of the burner’s axis relative to the engine axis with a low-swirl lifted spray flame. Here, the combustion can be stabilized at very low equivalence ratios thanks to the interaction between consecutive burners. A numerical analysis was carried out to support the experimental campaign aiming to investigate the performance of the burner under different tilting angles for the burners. Two-phase simulations of the CHAiRLIFT full rig burner were performed in the commercial CFD suite ANSYS Fluent and the results were compared with the available experimental data. Furthermore, a deeper sensitivity to the tilting angle was conducted through the introduction of specific performance parameters to assess the performance and to seek the best promising setup. The outcomes have shown that tilt angles between 20° and 30° could lead to an improvement of the exhaust recirculation, regarding the considered operating conditions.
{"title":"Numerical Modeling of Lean Spray Lifted Flames in Inclined Multi-Burner Arrangements","authors":"L. Langone, M. Amerighi, A. Andreini","doi":"10.1115/gt2022-82102","DOIUrl":"https://doi.org/10.1115/gt2022-82102","url":null,"abstract":"\u0000 Modern combustors operate with lean mixtures to prevent Nitrogen oxides (NOx) formation by limiting the peaks of the temperature inside the combustion chamber. One of the main drawbacks of these technologies is the higher risk of Lean Blow-Off (LBO) compared to the state-of-art Rich Quench Lean combustors. To limit this possibility, combustor designers introduced pioneering concepts for this component. In this fashion, the CHAiRLIFT (Compact Helical Arranged combustoRs with lean LIFTed flames) concept founds its advantages in the structure of the combustion chamber. It combines two concepts: the tilting of the burner’s axis relative to the engine axis with a low-swirl lifted spray flame. Here, the combustion can be stabilized at very low equivalence ratios thanks to the interaction between consecutive burners. A numerical analysis was carried out to support the experimental campaign aiming to investigate the performance of the burner under different tilting angles for the burners. Two-phase simulations of the CHAiRLIFT full rig burner were performed in the commercial CFD suite ANSYS Fluent and the results were compared with the available experimental data. Furthermore, a deeper sensitivity to the tilting angle was conducted through the introduction of specific performance parameters to assess the performance and to seek the best promising setup. The outcomes have shown that tilt angles between 20° and 30° could lead to an improvement of the exhaust recirculation, regarding the considered operating conditions.","PeriodicalId":395231,"journal":{"name":"Volume 3B: Combustion, Fuels, and Emissions","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130301619","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Benjamin Witzel, Daniel Moëll, N. Parsania, Ertan Yilmaz, Michael Koenig
Siemens Energy is developing the required technologies to operate its gas turbines on up to 100% H2 by 2030 to support the target of limiting global warming to 1.5 degrees Celsius. A focused effort has been undertaken to develop a technology platform for the Siemens Energy GT portfolio which will enable GT operation across the entire range H2/natural gas blends within emissions compliance. A first engine demonstration of these technologies in an industrial application will be conducted in an SGT-400 engine in 2023 as part of HYFLEXPOWER, an EU Horizon 2020 funded consortium project. This paper will present the results of numerical and experimental investigations of several candidate dry low NOx technologies. The candidate technologies are all lean, premixed designs and include: a swirled flame primary stage, a jet-based flame primary stage and an axial stage. The experimental results are conducted at elevated pressure and temperature conditions representative of the Siemens Energy gas turbine fleet. Additionally, a comparison of different kinetics mechanisms which offer the potential to accurately model flames burning H2, natural gases, and combinations of these fuels will be presented. The mechanisms include GRI 3.0 as well as three mechanisms which have been previously developed to improve the accuracy with high H2 content fuels.
{"title":"Development of a Fuel Flexible H2-Natural Gas Gas Turbine Combustion Technology Platform","authors":"Benjamin Witzel, Daniel Moëll, N. Parsania, Ertan Yilmaz, Michael Koenig","doi":"10.1115/gt2022-82881","DOIUrl":"https://doi.org/10.1115/gt2022-82881","url":null,"abstract":"\u0000 Siemens Energy is developing the required technologies to operate its gas turbines on up to 100% H2 by 2030 to support the target of limiting global warming to 1.5 degrees Celsius. A focused effort has been undertaken to develop a technology platform for the Siemens Energy GT portfolio which will enable GT operation across the entire range H2/natural gas blends within emissions compliance. A first engine demonstration of these technologies in an industrial application will be conducted in an SGT-400 engine in 2023 as part of HYFLEXPOWER, an EU Horizon 2020 funded consortium project.\u0000 This paper will present the results of numerical and experimental investigations of several candidate dry low NOx technologies. The candidate technologies are all lean, premixed designs and include: a swirled flame primary stage, a jet-based flame primary stage and an axial stage. The experimental results are conducted at elevated pressure and temperature conditions representative of the Siemens Energy gas turbine fleet. Additionally, a comparison of different kinetics mechanisms which offer the potential to accurately model flames burning H2, natural gases, and combinations of these fuels will be presented. The mechanisms include GRI 3.0 as well as three mechanisms which have been previously developed to improve the accuracy with high H2 content fuels.","PeriodicalId":395231,"journal":{"name":"Volume 3B: Combustion, Fuels, and Emissions","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132417443","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Meloni, S. Gori, G. Riccio, N. Chiarizia, D. Pampaloni, A. Andreini
In this paper, the numerical findings of a high fidelity CFD model will be compared with the experimental data of a test campaign devoted at characterizing the performance of a technically premixed industrial burner regarding the thermoacoustic instabilities. The data are retrieved at relevant gas turbine conditions in a test bench where the flame tube can change its length during the test execution allowing its fundamental acoustic frequencies to be modified and, in case, triggered. Mimicking the test configuration, several Large-Eddy Simulations are performed with different lengths of the flame tube in order to verify the ability of the numerical model to reproduce the excited dominant frequency and the corresponding limit cycle amplitude measurements. The numerical model demonstrates the ability to correctly reproduce the frequency triggered during the test and to reach different limit cycle amplitudes along different flame tube lengths in agreement with the tests, as well. However, it is found that the amplitude of the acoustic pressure fluctuation during the limit cycle is generally under-predicted. Despite this, the proposed approach demonstrates to be a robust tool for the characterization of a given design, allowing to dramatically reduce the computational cost of the analysis, at least in the early design phase. Since the numerical model can correctly reproduce the behavior of the investigated design, a deep post-processing of the solutions is performed to shed light on the physical mechanisms sustaining the thermo-acoustic instability. Among the numerical techniques employed at this purpose, the Phase-Locked Average and the Extended-POD are applied trying to correlate the fluctuations of the different quantities inside the premixed channel of the burner and the primary zone as well.
{"title":"Experimental and Numerical Characterization of the Self-Excited Dynamics Behavior of a Technically Premixed Burner","authors":"R. Meloni, S. Gori, G. Riccio, N. Chiarizia, D. Pampaloni, A. Andreini","doi":"10.1115/gt2022-82248","DOIUrl":"https://doi.org/10.1115/gt2022-82248","url":null,"abstract":"\u0000 In this paper, the numerical findings of a high fidelity CFD model will be compared with the experimental data of a test campaign devoted at characterizing the performance of a technically premixed industrial burner regarding the thermoacoustic instabilities.\u0000 The data are retrieved at relevant gas turbine conditions in a test bench where the flame tube can change its length during the test execution allowing its fundamental acoustic frequencies to be modified and, in case, triggered. Mimicking the test configuration, several Large-Eddy Simulations are performed with different lengths of the flame tube in order to verify the ability of the numerical model to reproduce the excited dominant frequency and the corresponding limit cycle amplitude measurements. The numerical model demonstrates the ability to correctly reproduce the frequency triggered during the test and to reach different limit cycle amplitudes along different flame tube lengths in agreement with the tests, as well. However, it is found that the amplitude of the acoustic pressure fluctuation during the limit cycle is generally under-predicted. Despite this, the proposed approach demonstrates to be a robust tool for the characterization of a given design, allowing to dramatically reduce the computational cost of the analysis, at least in the early design phase.\u0000 Since the numerical model can correctly reproduce the behavior of the investigated design, a deep post-processing of the solutions is performed to shed light on the physical mechanisms sustaining the thermo-acoustic instability. Among the numerical techniques employed at this purpose, the Phase-Locked Average and the Extended-POD are applied trying to correlate the fluctuations of the different quantities inside the premixed channel of the burner and the primary zone as well.","PeriodicalId":395231,"journal":{"name":"Volume 3B: Combustion, Fuels, and Emissions","volume":"4168 1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127563602","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
High-frequency transverse instabilities are an important concern in can combustor configurations. In these configurations which are typically operated with multiple injectors around a central injector, each injector is subjected to different parts of the acoustic mode shape and thus respond differently for the same instability mode. Recent work by the author has modeled the response of premixed flames to excitation by natural high-frequency transverse modes in a can combustor both in the center and outer nozzles. The stability of these acoustically non-compact flames was assessed using the Rayleigh criterion (Rayleigh Integral denoted as RI) and not the overall unsteady heat release as is the case for compact flames. Several key control parameters were studied, namely — flame angle, swirling strength, nozzle location. For non-axisymmetric modes such as the commonly occurring 1-T mode, both radial and azimuthal offsets of the nozzle location affected stability. The framework was applied to an optimization study to identify the optimal combination of parameters that minimizes RI for the different nozzles in the multi-nozzle system. In this study, a N-around-1 configuration was studied, and the results indicated that the different nozzles needed to be operated at different flame angles and swirl numbers to result in an overall minimum RI. However, the specific response of the different injectors was not considered. The helical mode distribution at each injector varies as we azimuthally go around the combustor’s injector distribution and thus the most amplified mode and the resulting flame response would be different. To minimize RI, it is important to determine the injector configurations that result in a hydrodynamic profile that minimizes the individual RI for each nozzle. The resulting relationship between the injector’s flow and local hydrodynamics can then be used in a hydrodynamics study of an individual injector so that the most optimal injector is chosen depending on its location in the combustor dump plane.
{"title":"Optimum Injector Parameters for Thermoacoustic Stability in a Multi-Nozzle Can Combustion System","authors":"V. Acharya","doi":"10.1115/gt2022-83392","DOIUrl":"https://doi.org/10.1115/gt2022-83392","url":null,"abstract":"\u0000 High-frequency transverse instabilities are an important concern in can combustor configurations. In these configurations which are typically operated with multiple injectors around a central injector, each injector is subjected to different parts of the acoustic mode shape and thus respond differently for the same instability mode. Recent work by the author has modeled the response of premixed flames to excitation by natural high-frequency transverse modes in a can combustor both in the center and outer nozzles. The stability of these acoustically non-compact flames was assessed using the Rayleigh criterion (Rayleigh Integral denoted as RI) and not the overall unsteady heat release as is the case for compact flames. Several key control parameters were studied, namely — flame angle, swirling strength, nozzle location. For non-axisymmetric modes such as the commonly occurring 1-T mode, both radial and azimuthal offsets of the nozzle location affected stability. The framework was applied to an optimization study to identify the optimal combination of parameters that minimizes RI for the different nozzles in the multi-nozzle system. In this study, a N-around-1 configuration was studied, and the results indicated that the different nozzles needed to be operated at different flame angles and swirl numbers to result in an overall minimum RI. However, the specific response of the different injectors was not considered. The helical mode distribution at each injector varies as we azimuthally go around the combustor’s injector distribution and thus the most amplified mode and the resulting flame response would be different. To minimize RI, it is important to determine the injector configurations that result in a hydrodynamic profile that minimizes the individual RI for each nozzle. The resulting relationship between the injector’s flow and local hydrodynamics can then be used in a hydrodynamics study of an individual injector so that the most optimal injector is chosen depending on its location in the combustor dump plane.","PeriodicalId":395231,"journal":{"name":"Volume 3B: Combustion, Fuels, and Emissions","volume":"127 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116322710","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ishan Verma, Rakesh Yadav, N. Ansari, Stefano Orsino, Shaoping Li, Pravin M. Nakod
Due to its clean combustion characteristics, hydrogen fuel is gaining attention in power generation. New designs of engine systems and components are being explored to allow blending with the increasing amount of hydrogen in natural gas. Adding H2 increases the probability of flashback and often is one of the main constraints in using high H2 blends in premixed combustors. There are several mechanisms of flashback like boundary layer flashback, combustion induced vortex break down, turbulence in the flow, fluctuations in equivalence ratio, etc. Semi-empirical models, based on non-dimensional numbers and flame speed, have successfully predicted flashback propensity for a given operating condition. The semi-empirical models are computationally very efficient; however, they lack generality. A typical combustor can have multiple flashback mechanisms. The relative importance of each mechanism can change with a change in the combustor design or even with a difference in the operating conditions for the same combustor. Since prediction of flashback requires accurate modeling of highly transient chemistry phenomena and the impact of heat loss on chemistry, a viable detailed chemistry solution is preferred to model flashback. This paper describes the use of a finite rate chemistry model to predict flashbacks in a turbulent premixed combustor in this work. The configuration used is a swirl stabilized combustor (SimVal) from National Energy Technology Laboratory. The current computations are done with Finite Rate Chemistry (FRC) and Large Eddy Simulations (LES). Simulations are carried out for a varied percentage of CH4/H2 blends, ranging from 0% H2 to 100% H2 at a fixed equivalence ratio and inlet mass flow. As the percentage of H2 is increased in the fuel, flame speed also increases. With this, the propensity for flashbacks also increases. A 28-species reduced mechanism for CH4/H2 blend flames is used to keep the simulations computationally tractable. The simulations with the reduced mechanism are performed by considering non-adiabatic effects from heat loss near the walls and multi-component property considerations. This improves the accuracy of the FRC-LES simulations to capture the onset of boundary layer flashback towards the inlet. The simulations from FRC-LES suggest a fine mesh in the boundary layer for an accurate prediction that makes the simulations expensive. Therefore, an Adaptive Mesh Refinement (AMR) approach has been used for different CH4/H2 blends to accurately model the flashback without any loss in generality as the AMR criteria used here are applicable for a wide range of conditions. The FRC-based solution strategy proposed in this work provides a framework to model flashback for different blends without any case-specific tuning.
{"title":"Modeling of Flashback With Different Blends of CH4 and H2 by Using Finite Rate Chemistry With Large Eddy Simulation","authors":"Ishan Verma, Rakesh Yadav, N. Ansari, Stefano Orsino, Shaoping Li, Pravin M. Nakod","doi":"10.1115/gt2022-82601","DOIUrl":"https://doi.org/10.1115/gt2022-82601","url":null,"abstract":"\u0000 Due to its clean combustion characteristics, hydrogen fuel is gaining attention in power generation. New designs of engine systems and components are being explored to allow blending with the increasing amount of hydrogen in natural gas. Adding H2 increases the probability of flashback and often is one of the main constraints in using high H2 blends in premixed combustors. There are several mechanisms of flashback like boundary layer flashback, combustion induced vortex break down, turbulence in the flow, fluctuations in equivalence ratio, etc. Semi-empirical models, based on non-dimensional numbers and flame speed, have successfully predicted flashback propensity for a given operating condition. The semi-empirical models are computationally very efficient; however, they lack generality. A typical combustor can have multiple flashback mechanisms. The relative importance of each mechanism can change with a change in the combustor design or even with a difference in the operating conditions for the same combustor. Since prediction of flashback requires accurate modeling of highly transient chemistry phenomena and the impact of heat loss on chemistry, a viable detailed chemistry solution is preferred to model flashback.\u0000 This paper describes the use of a finite rate chemistry model to predict flashbacks in a turbulent premixed combustor in this work. The configuration used is a swirl stabilized combustor (SimVal) from National Energy Technology Laboratory. The current computations are done with Finite Rate Chemistry (FRC) and Large Eddy Simulations (LES). Simulations are carried out for a varied percentage of CH4/H2 blends, ranging from 0% H2 to 100% H2 at a fixed equivalence ratio and inlet mass flow. As the percentage of H2 is increased in the fuel, flame speed also increases. With this, the propensity for flashbacks also increases. A 28-species reduced mechanism for CH4/H2 blend flames is used to keep the simulations computationally tractable. The simulations with the reduced mechanism are performed by considering non-adiabatic effects from heat loss near the walls and multi-component property considerations. This improves the accuracy of the FRC-LES simulations to capture the onset of boundary layer flashback towards the inlet. The simulations from FRC-LES suggest a fine mesh in the boundary layer for an accurate prediction that makes the simulations expensive. Therefore, an Adaptive Mesh Refinement (AMR) approach has been used for different CH4/H2 blends to accurately model the flashback without any loss in generality as the AMR criteria used here are applicable for a wide range of conditions. The FRC-based solution strategy proposed in this work provides a framework to model flashback for different blends without any case-specific tuning.","PeriodicalId":395231,"journal":{"name":"Volume 3B: Combustion, Fuels, and Emissions","volume":"61 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114326252","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Weijie Liu, M. Jin, B. Ge, Ranran Xue, He Su, S. Zang
Flame response is a key element in predicting thermoacoustic instabilities in gas turbine combustors. Flame dynamic response of single swirling flames to acoustic excitation was well studied in the past decades, while the unsteady dynamic of multi-swirling flames, such as stratified flames, is not fully reported. This paper presents dynamic response of stratified flames in a multi-swirler combustor which includes a main stage and a pilot stage. The stratified flame contains an outer main flame and an inner pilot flame. The overall Flame Transfer Function (FTF) of the stratified flame is extracted during the experiment. High-speed camera and high-frequency Particle Image Velocimetry (PIV) are used to capture the evolution of the flame and flow structure. Experimental results show the overall flame transfer function of the stratified flame features several discrete peaks and valleys in a narrow frequency range which is slightly different with a typical simple swirling flame. The main flame is stabilized at the inner shear layer region of the main flow while the pilot flame settles at a position where turbulent flame speed equals to the local pilot flow speed. The effect of the acoustic driving on the topology structure of the stratified flame is not apparent. Proper orthogonal decomposition of the stratified flame shows a wave of alternating positive and negative values across the flame indicating flame fluctuations are in axial modes. Proper orthogonal decomposition of the multi-swirling flow reveals coherent structures are formed in the shear layer of the main flow which dominates the stratified flame response.
{"title":"Dynamic Response of Stratified Flames to Acoustic Excitation in a Multi-Swirler Model Combustor","authors":"Weijie Liu, M. Jin, B. Ge, Ranran Xue, He Su, S. Zang","doi":"10.1115/gt2022-82871","DOIUrl":"https://doi.org/10.1115/gt2022-82871","url":null,"abstract":"\u0000 Flame response is a key element in predicting thermoacoustic instabilities in gas turbine combustors. Flame dynamic response of single swirling flames to acoustic excitation was well studied in the past decades, while the unsteady dynamic of multi-swirling flames, such as stratified flames, is not fully reported. This paper presents dynamic response of stratified flames in a multi-swirler combustor which includes a main stage and a pilot stage. The stratified flame contains an outer main flame and an inner pilot flame. The overall Flame Transfer Function (FTF) of the stratified flame is extracted during the experiment. High-speed camera and high-frequency Particle Image Velocimetry (PIV) are used to capture the evolution of the flame and flow structure.\u0000 Experimental results show the overall flame transfer function of the stratified flame features several discrete peaks and valleys in a narrow frequency range which is slightly different with a typical simple swirling flame. The main flame is stabilized at the inner shear layer region of the main flow while the pilot flame settles at a position where turbulent flame speed equals to the local pilot flow speed. The effect of the acoustic driving on the topology structure of the stratified flame is not apparent. Proper orthogonal decomposition of the stratified flame shows a wave of alternating positive and negative values across the flame indicating flame fluctuations are in axial modes. Proper orthogonal decomposition of the multi-swirling flow reveals coherent structures are formed in the shear layer of the main flow which dominates the stratified flame response.","PeriodicalId":395231,"journal":{"name":"Volume 3B: Combustion, Fuels, and Emissions","volume":"108 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126023399","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
I. Carlos, L. Witherspoon, L. Cowell, Priyanka Saxena
Formaldehyde is listed as a Hazardous Air Pollutant (HAP) by various regulatory agencies around the world because of its role as a carcinogen. To address this impact, several countries have regulated formaldehyde emissions from land-based gas turbines. In the United States (U.S.), the federal regulatory level is 91 ppb and state level formaldehyde requirements vary significantly. In Germany, the formaldehyde limit is 5 mg/Nm3 (∼3.7 ppm) from 70–100% load. Formaldehyde emissions from gas turbines are formed due to incomplete combustion of natural gas and predictably track with carbon monoxide (CO) and unburned hydrocarbon (UHC) emissions trends. This paper presents results from a formaldehyde measurement campaign completed in test cells at Solar Turbines on Dry Low Emissions (DLE) turbine products including the Mars® 100, Titan™ 130 and Titan™ 250 operating on pipeline natural gas. Theoretical modeling of formaldehyde formation using a Chemical Reactor Network (CRN) model are also presented. Measurements have been taken in the engine test cells over a range of operating conditions from full load* to idle. The latest Fourier Transform Infrared (FTIR) technology has been used to meet the challenges of accurately measuring formaldehyde down to the 10-ppb detection level. Formaldehyde emissions were found to range from near the detection limit to 50 ppb at full load with a small increase as load is decreased within the typical DLE operating range and a sharper increase outside of DLE mode to idle. The variation is attributed to differences between gas turbine models based on pressure ratio and combustion system design. CRN modeling predictions were compared with the test data, and the modeling results were used to gain insight into the formaldehyde emissions formation mechanisms.
{"title":"Formaldehyde Emissions from Dry Low Emissions Industrial Gas Turbines","authors":"I. Carlos, L. Witherspoon, L. Cowell, Priyanka Saxena","doi":"10.1115/gt2022-82735","DOIUrl":"https://doi.org/10.1115/gt2022-82735","url":null,"abstract":"\u0000 Formaldehyde is listed as a Hazardous Air Pollutant (HAP) by various regulatory agencies around the world because of its role as a carcinogen. To address this impact, several countries have regulated formaldehyde emissions from land-based gas turbines. In the United States (U.S.), the federal regulatory level is 91 ppb and state level formaldehyde requirements vary significantly. In Germany, the formaldehyde limit is 5 mg/Nm3 (∼3.7 ppm) from 70–100% load. Formaldehyde emissions from gas turbines are formed due to incomplete combustion of natural gas and predictably track with carbon monoxide (CO) and unburned hydrocarbon (UHC) emissions trends. This paper presents results from a formaldehyde measurement campaign completed in test cells at Solar Turbines on Dry Low Emissions (DLE) turbine products including the Mars® 100, Titan™ 130 and Titan™ 250 operating on pipeline natural gas. Theoretical modeling of formaldehyde formation using a Chemical Reactor Network (CRN) model are also presented. Measurements have been taken in the engine test cells over a range of operating conditions from full load* to idle. The latest Fourier Transform Infrared (FTIR) technology has been used to meet the challenges of accurately measuring formaldehyde down to the 10-ppb detection level. Formaldehyde emissions were found to range from near the detection limit to 50 ppb at full load with a small increase as load is decreased within the typical DLE operating range and a sharper increase outside of DLE mode to idle. The variation is attributed to differences between gas turbine models based on pressure ratio and combustion system design. CRN modeling predictions were compared with the test data, and the modeling results were used to gain insight into the formaldehyde emissions formation mechanisms.","PeriodicalId":395231,"journal":{"name":"Volume 3B: Combustion, Fuels, and Emissions","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129718068","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Patwardhan, Pravin M. Nakod, Stefano Orsino, Rakesh Yadav, Fang Xu, Dustin M. Brandt
Emission standard agencies are coming up with more stringent regulations on Nitrogen Oxides (NOx), given their adverse effect on the environment. The aircraft engines operate at varying operating conditions and temperature-dependent emissions like NOx are significantly affected by varying conditions. Computational Fluid Dynamics (CFD) simulations are playing a key role in the design of gas turbine combustors and an accurate NOx model will be an important tool for the designers. The new stringent regulations will require new computational approaches over the traditional methods so that the NOx can be predicted accurately under a wide range of operating conditions. Traditionally, the high temperature NOx is predicted using a three-step Zeldovich mechanism. However, it has been observed that the NO (Nitrogen oxide) mass fraction predicted by the Zeldovich mechanism is not accurate for low power conditions due to its predominantly high-temperature kinetics. A significant amount of NO2 (Nitrogen dioxide) is observed in the experimental data at lower temperatures. This requires the inclusion of NO2 chemistry in the NOx mechanism. With the increase in the available computational power, a detailed chemistry simulation is gaining attention, especially for pollutant prediction. In this work, we explore the finite rate (FR) chemistry approach for the prediction of total NOx (NO + NO2) in a gas turbine combustor designed for Aerospace applications. Two reduced mechanisms are investigated namely, the PERK mechanism with 31 species and the Hychem mechanism with 71 species. Simulations with both mechanisms show good comparison with the experimental data and predict the individual contribution of NO and NO2 reasonably well. Further, it is observed that the spray breakup model has a significant impact on the NOx prediction, and it is important to capture the fuel spray correctly to predict the right amount of NOx.
考虑到氮氧化物(NOx)对环境的不良影响，排放标准机构正在制定更严格的规定。飞机发动机在不同的工作条件下运行，而与温度相关的排放物，如氮氧化物，会受到不同条件的显著影响。计算流体动力学(CFD)模拟在燃气轮机燃烧室设计中起着关键作用，准确的NOx模型将成为设计人员的重要工具。新的严格规定将需要新的计算方法，而不是传统方法，以便在广泛的操作条件下准确预测氮氧化物。传统上，高温NOx的预测使用三步Zeldovich机制。然而，由于其主要是高温动力学，Zeldovich机制预测的NO(氮氧化物)质量分数在低功率条件下是不准确的。在较低温度下的实验数据中观察到大量的NO2(二氧化氮)。这需要在NOx机制中包含NO2化学。随着可用计算能力的提高，详细的化学模拟越来越受到关注，特别是对污染物的预测。在这项工作中，我们探索了有限速率(FR)化学方法来预测为航空航天应用而设计的燃气轮机燃烧室中的总NOx (NO + NO2)。研究了两种还原机制，即31种PERK机制和71种Hychem机制。两种机制的模拟结果与实验数据比较吻合，较好地预测了NO和NO2的个体贡献。此外，喷雾破碎模型对NOx预测有重要影响，正确捕获燃料喷雾对预测正确的NOx量至关重要。
{"title":"Predicting NOx Emissions In Gas Turbines Using Finite Rate Approach","authors":"S. Patwardhan, Pravin M. Nakod, Stefano Orsino, Rakesh Yadav, Fang Xu, Dustin M. Brandt","doi":"10.1115/gt2022-82622","DOIUrl":"https://doi.org/10.1115/gt2022-82622","url":null,"abstract":"\u0000 Emission standard agencies are coming up with more stringent regulations on Nitrogen Oxides (NOx), given their adverse effect on the environment. The aircraft engines operate at varying operating conditions and temperature-dependent emissions like NOx are significantly affected by varying conditions. Computational Fluid Dynamics (CFD) simulations are playing a key role in the design of gas turbine combustors and an accurate NOx model will be an important tool for the designers. The new stringent regulations will require new computational approaches over the traditional methods so that the NOx can be predicted accurately under a wide range of operating conditions.\u0000 Traditionally, the high temperature NOx is predicted using a three-step Zeldovich mechanism. However, it has been observed that the NO (Nitrogen oxide) mass fraction predicted by the Zeldovich mechanism is not accurate for low power conditions due to its predominantly high-temperature kinetics. A significant amount of NO2 (Nitrogen dioxide) is observed in the experimental data at lower temperatures. This requires the inclusion of NO2 chemistry in the NOx mechanism. With the increase in the available computational power, a detailed chemistry simulation is gaining attention, especially for pollutant prediction. In this work, we explore the finite rate (FR) chemistry approach for the prediction of total NOx (NO + NO2) in a gas turbine combustor designed for Aerospace applications. Two reduced mechanisms are investigated namely, the PERK mechanism with 31 species and the Hychem mechanism with 71 species. Simulations with both mechanisms show good comparison with the experimental data and predict the individual contribution of NO and NO2 reasonably well. Further, it is observed that the spray breakup model has a significant impact on the NOx prediction, and it is important to capture the fuel spray correctly to predict the right amount of NOx.","PeriodicalId":395231,"journal":{"name":"Volume 3B: Combustion, Fuels, and Emissions","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124966151","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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