This paper presents a comprehensive validation and verification study of turbomachinery Reynolds-averaged Navier-Stokes flow solvers on the transonic axial compressor TUDa-GLR-OpenStage. Two commercial solvers namely Ansys CFX and Numeca FineTurbo are adopted to provide the benchmark solutions, which can be used for verification of other RANS solvers in the future. Based on these solvers, five sets of grids, two advection schemes (i.e., central difference and second-order upwind), four turbulence models (i.e., SA, SA-RC, SST and EARSM) and two rotor-stator interface models (i.e., mixing plane and sliding plane) are investigated to quantify their effects on predicting the performance and the flow field of the compressor stage. Results show that the choices of grid density and turbulence model are most sensitive to the prediction, leading to 5% and 7% variation in compressor performance characteristics, respectively. Regarding the choice of grid density, a method to estimate the grid discretization error is demonstrated, which is transferrable to other cases. Regarding the choice of turbulence model, the EARSM model is found overall most accurate among the investigated models, and the limitations and deficiencies of the rest models are discussed in detail based on the analysis of the mean flow fields and the eddy viscosity fields. The grids and the major CFD results presented in this work are open-accessed to the community for further research. The results and discussions presented in this paper provide a useful reference for future practices of RANS simulations for compressors.
{"title":"Validation and verification of RANS solvers for TUDa-GLR-OpenStage transonic axial compressor","authors":"Xiao He, Mingmin Zhu, Kailong Xia, Klausmann Fabian, Jinfang Teng, Mehdi Vahdati","doi":"10.33737/jgpps/158034","DOIUrl":"https://doi.org/10.33737/jgpps/158034","url":null,"abstract":"This paper presents a comprehensive validation and verification study of turbomachinery Reynolds-averaged Navier-Stokes flow solvers on the transonic axial compressor TUDa-GLR-OpenStage. Two commercial solvers namely Ansys CFX and Numeca FineTurbo are adopted to provide the benchmark solutions, which can be used for verification of other RANS solvers in the future. Based on these solvers, five sets of grids, two advection schemes (i.e., central difference and second-order upwind), four turbulence models (i.e., SA, SA-RC, SST and EARSM) and two rotor-stator interface models (i.e., mixing plane and sliding plane) are investigated to quantify their effects on predicting the performance and the flow field of the compressor stage. Results show that the choices of grid density and turbulence model are most sensitive to the prediction, leading to 5% and 7% variation in compressor performance characteristics, respectively. Regarding the choice of grid density, a method to estimate the grid discretization error is demonstrated, which is transferrable to other cases. Regarding the choice of turbulence model, the EARSM model is found overall most accurate among the investigated models, and the limitations and deficiencies of the rest models are discussed in detail based on the analysis of the mean flow fields and the eddy viscosity fields. The grids and the major CFD results presented in this work are open-accessed to the community for further research. The results and discussions presented in this paper provide a useful reference for future practices of RANS simulations for compressors.","PeriodicalId":53002,"journal":{"name":"Journal of the Global Power and Propulsion Society","volume":"671 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135743532","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}
The unsteady leakage flow and heat transfer characteristics of the turbine blade squealer tip was numerically investigated using three-dimensional Unsteady Reynolds-Averaged Naiver-Stokes (URANS) and standard k-ω turbulence model. The numerical simulated heat transfer coefficients of the turbine blade tip were well agreement with the experimental data. The accuracy of the numerical method was validated. The steady and unsteady leakage flow and heat transfer coefficient of the turbine blade squealer tip with and without film cooling was conducted. The unsteady leakage flow and heat transfer characteristics of the turbine blade squealer tip with film cooling design at three different blow ratios was numerically investigated. The obtained results show that the corner vortex and scraping vortex near the pressure side shows periodic fluctuation along the separation line of the leakage flow under the function of the pressure difference between the suction and pressure side of the blade tip, as well as the upstream vane unsteady wake flow. This unsteady flow behavior results in the fluctuation of the high heat transfer coefficients at the blade tip. The film cooling design along the camber line can effectively reduce the thermal load of the turbine blade squealer tip by comparison to without film cooling case. The time-averaged heat transfer coefficients of the turbine blade squealer tip reduce 9.0%, 12.4% and 13.2% at blowing ratio of .0.5, 1.0 and 1.5 comparison to without film cooling design in respective. The present work can provide the reference of the film cooling design for the turbine blade squealer tip.
采用三维非定常reynolds - average naver - stokes (URANS)和标准k-ω湍流模型，对涡轮叶片尖部的非定常泄漏流动和换热特性进行了数值研究。数值模拟的涡轮叶尖换热系数与实验数据吻合较好。验证了数值方法的准确性。研究了采用气膜冷却和不采用气膜冷却的涡轮叶片尖部的定常和非定常泄漏流量和换热系数。对采用气膜冷却设计的涡轮叶片尖部在三种不同吹风比下的非定常泄漏流动和换热特性进行了数值研究。得到的结果表明，在叶尖吸力与压力侧压差以及上游叶片非定常尾流的作用下，压力侧附近的角涡和刮涡沿泄漏流分离线呈现周期性波动。这种非定常流动行为导致了叶顶高换热系数的波动。与无气膜冷却情况相比，沿弧度线的气膜冷却设计能有效降低涡轮叶片尖尖的热负荷。在吹气比为0.0.5、1.0和1.5时，涡轮叶片尖部的时间平均换热系数分别比无气膜冷却设计降低9.0%、12.4%和13.2%。本文的工作可为涡轮叶片尖部的气膜冷却设计提供参考。
{"title":"Numerical investigations on the unsteady leakage flow and heat transfer characteristics of the turbine blade squealer tip","authors":"Shijie Jiang, Zhigang Li, Jun Li, Liming Song","doi":"10.33737/jgpps/157176","DOIUrl":"https://doi.org/10.33737/jgpps/157176","url":null,"abstract":"The unsteady leakage flow and heat transfer characteristics of the turbine blade squealer tip was numerically investigated using three-dimensional Unsteady Reynolds-Averaged Naiver-Stokes (URANS) and standard k-ω turbulence model. The numerical simulated heat transfer coefficients of the turbine blade tip were well agreement with the experimental data. The accuracy of the numerical method was validated. The steady and unsteady leakage flow and heat transfer coefficient of the turbine blade squealer tip with and without film cooling was conducted. The unsteady leakage flow and heat transfer characteristics of the turbine blade squealer tip with film cooling design at three different blow ratios was numerically investigated. The obtained results show that the corner vortex and scraping vortex near the pressure side shows periodic fluctuation along the separation line of the leakage flow under the function of the pressure difference between the suction and pressure side of the blade tip, as well as the upstream vane unsteady wake flow. This unsteady flow behavior results in the fluctuation of the high heat transfer coefficients at the blade tip. The film cooling design along the camber line can effectively reduce the thermal load of the turbine blade squealer tip by comparison to without film cooling case. The time-averaged heat transfer coefficients of the turbine blade squealer tip reduce 9.0%, 12.4% and 13.2% at blowing ratio of .0.5, 1.0 and 1.5 comparison to without film cooling design in respective. The present work can provide the reference of the film cooling design for the turbine blade squealer tip.","PeriodicalId":53002,"journal":{"name":"Journal of the Global Power and Propulsion Society","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135323557","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}
Nowadays, in order to achieve higher efficiency in aero-engines, the increase of turbine inlet temperature in aero-engine is in urgent need. At present, the turbine inlet temperature is around 2,000 K, which means the radiation and coupled radiation-conduction heat transfer play more and more important roles in hot section of aero-engines. As we all konw, considering the cylindrical symmetry of aero-engines. It is convenient to adopt the cylindrical coordinate to simplify the description of these systems, such as annular combustor, exhaust nozzle, etc. In this paper, Discontinuous Spectral Element Method (DSEM) is extended to solve the radiation and coupled radiation-coduction heat transfer in cylindrical coordinate system. Both the spatial and angular computational domains of radiative transfer equation (RTE) are discretized and solved by DSEM. For coupled radiation-conduction heat transfer problem, Discontinuous Spectral Element Method-Spectral Element Method (DSEM-SEM) scheme is used to avoid using two sets of grid which would cause the increase of computational cost and the decrease of accuracy. Then, the effects of various geometric and thermal physical parameters are comprehensively investigated. Finally, these methods are further extended to 2D cylindrical system.
{"title":"Investigation of coupled radiation-conduction heat transfer in cylindrical systems by discontinuous spectral element method","authors":"Jiazi Zhao, Yasong Sun, Yifang Li, Changhao Liu","doi":"10.33737/jgpps/156350","DOIUrl":"https://doi.org/10.33737/jgpps/156350","url":null,"abstract":"Nowadays, in order to achieve higher efficiency in aero-engines, the increase of turbine inlet temperature in aero-engine is in urgent need. At present, the turbine inlet temperature is around 2,000 K, which means the radiation and coupled radiation-conduction heat transfer play more and more important roles in hot section of aero-engines. As we all konw, considering the cylindrical symmetry of aero-engines. It is convenient to adopt the cylindrical coordinate to simplify the description of these systems, such as annular combustor, exhaust nozzle, etc. In this paper, Discontinuous Spectral Element Method (DSEM) is extended to solve the radiation and coupled radiation-coduction heat transfer in cylindrical coordinate system. Both the spatial and angular computational domains of radiative transfer equation (RTE) are discretized and solved by DSEM. For coupled radiation-conduction heat transfer problem, Discontinuous Spectral Element Method-Spectral Element Method (DSEM-SEM) scheme is used to avoid using two sets of grid which would cause the increase of computational cost and the decrease of accuracy. Then, the effects of various geometric and thermal physical parameters are comprehensively investigated. Finally, these methods are further extended to 2D cylindrical system.","PeriodicalId":53002,"journal":{"name":"Journal of the Global Power and Propulsion Society","volume":" ","pages":""},"PeriodicalIF":0.9,"publicationDate":"2022-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41970774","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 heavy gas turbine combustors are always huge, so it is difficult and costly to do experiment. Thus, geometry scaling method has come into sight. In this paper, based on a single lean premixed swirl burner, validated computational fluid dynamic (CFD) model was used to study the effects of different scaling laws on various scalling models from 1/2 to 1/10. Experimental study on prototype combustor and the 3/5 scale model under full operating condition is also carried out to verify the NOx emission under different laws. Results showed that DaI scaling law was able to maintain good similarity under combustion state when scaling factor = 1/2–1/5, while Re scaling law would bring significant changes on flow and flame characteristics. The emission of NOx is also similar to prototype by using Dai law. But Re law could keep flow characteristics under non-combustion state. It is suggested that Dai law is suitable for lean premixed swirl combustor geometry scaling.
{"title":"Effects of scaling laws on flow and combustion characteristics of lean premixed swirl burners","authors":"Wenda Xie, Ting Shi, B. Ge, S. Zang","doi":"10.33737/jgpps/156121","DOIUrl":"https://doi.org/10.33737/jgpps/156121","url":null,"abstract":"Modern heavy gas turbine combustors are always huge, so it is difficult and costly to do experiment. Thus, geometry scaling method has come into sight. In this paper, based on a single lean premixed swirl burner, validated computational fluid dynamic (CFD) model was used to study the effects of different scaling laws on various scalling models from 1/2 to 1/10. Experimental study on prototype combustor and the 3/5 scale model under full operating condition is also carried out to verify the NOx emission under different laws. Results showed that DaI scaling law was able to maintain good similarity under combustion state when scaling factor = 1/2–1/5, while Re scaling law would bring significant changes on flow and flame characteristics. The emission of NOx is also similar to prototype by using Dai law. But Re law could keep flow characteristics under non-combustion state. It is suggested that Dai law is suitable for lean premixed swirl combustor geometry scaling.","PeriodicalId":53002,"journal":{"name":"Journal of the Global Power and Propulsion Society","volume":" ","pages":""},"PeriodicalIF":0.9,"publicationDate":"2022-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45775813","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}
This paper presents detailed validations of a Large Eddy Simulation (LES) methodology for various transitional phenomena in low pressure turbines. The results are discussed to identify key phenomena to be resolved accurately toward future industrial use of LES. Detailed comparisons between experimental and CFD results are made on three different 2D cascades with different blade loading. One is low-lift and fully laminar design, while the others are moderate- and high-lift designs with boundary layer transition. The experimental data are obtained in a low speed linear cascade at Iwate University. All computations are conducted by a carefully-designed overset LES code. For the high-load design with a distinct laminar separation on the suction side, the LES result shows satisfactory agreement with the test. However, although the peak of total pressure loss distribution is predicted quite accurately, integrated cascade losses are over-predicted in the other two cases. For the laminar blade, the LES result implies some differences can exist in the state of wake, while the transitional blade shows delay of transition in the boundary layer. The effects of inflow turbulence intensity, length scale, and stream tube contraction are discussed in detail to improve LES prediction.
{"title":"LES prediction of transitional flows in LP turbine cascades: effects of blade loading, flow phenomena and numerical setup","authors":"A. Tateishi, N. Tani, Y. Okamura, Masaaki Hamabe","doi":"10.33737/jgpps/156577","DOIUrl":"https://doi.org/10.33737/jgpps/156577","url":null,"abstract":"This paper presents detailed validations of a Large Eddy Simulation (LES) methodology for various transitional phenomena in low pressure turbines. The results are discussed to identify key phenomena to be resolved accurately toward future industrial use of LES. Detailed comparisons between experimental and CFD results are made on three different 2D cascades with different blade loading. One is low-lift and fully laminar design, while the others are moderate- and high-lift designs with boundary layer transition. The experimental data are obtained in a low speed linear cascade at Iwate University. All computations are conducted by a carefully-designed overset LES code. For the high-load design with a distinct laminar separation on the suction side, the LES result shows satisfactory agreement with the test. However, although the peak of total pressure loss distribution is predicted quite accurately, integrated cascade losses are over-predicted in the other two cases. For the laminar blade, the LES result implies some differences can exist in the state of wake, while the transitional blade shows delay of transition in the boundary layer. The effects of inflow turbulence intensity, length scale, and stream tube contraction are discussed in detail to improve LES prediction.","PeriodicalId":53002,"journal":{"name":"Journal of the Global Power and Propulsion Society","volume":" ","pages":""},"PeriodicalIF":0.9,"publicationDate":"2022-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42926492","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}
Fabian Klausmann, D. Franke, J. Foret, H. Schiffer
Designs for future aero engines aim for increased efficiency with reduced exhaust gas and noise emissions. To achieve these goals, comprehensive physical understanding and highly innovative solutions are necessary. Even though computational capabilities are rising, the required confidence level is restrained. To understand and validate theoretical and numerical models, extensive experiments at realistic operating conditions are crucial. The modular compressor at the Transonic Compressor Darmstadt test facility at Technical University of Darmstadt enables investigations of prototype BLISK rotors in single or 1.5-stage setups, operating at high-speed conditions. Extensive steady and time-resolving instrumentation is used to determine the compressor aerodynamics and performance as well as aeroelastics. To foster improvements in numerical modelling and predictability based on high quality experimental data, the TUDa-GLR-OpenStage test case is introduced. It comprises a single stage setup, including the BLISK rotor, a 3D-optimized stator as well as the annulus contour. The data set is supplemented with comprehensive measurement data at stage inlet and outlet as well as running tip clearances. This paper describes the open test case, related geometries, measurement procedures and corresponding experimental results, including steady state performance and unsteady aerodynamics. Ultimately, it is aiming to provide a standard case for future development of numerical models and comparable validation.
{"title":"Transonic compressor Darmstadt - Open test case\u0000\u0000Introduction of the TUDa open test case","authors":"Fabian Klausmann, D. Franke, J. Foret, H. Schiffer","doi":"10.33737/jgpps/156120","DOIUrl":"https://doi.org/10.33737/jgpps/156120","url":null,"abstract":"Designs for future aero engines aim for increased efficiency with reduced exhaust gas and noise emissions. To achieve these goals, comprehensive physical understanding and highly innovative solutions are necessary. Even though computational capabilities are rising, the required confidence level is restrained. To understand and validate theoretical and numerical models, extensive experiments at realistic operating conditions are crucial.\u0000\u0000The modular compressor at the Transonic Compressor Darmstadt test facility at Technical University of Darmstadt enables investigations of prototype BLISK rotors in single or 1.5-stage setups, operating at high-speed conditions. Extensive steady and time-resolving instrumentation is used to determine the compressor aerodynamics and performance as well as aeroelastics.\u0000\u0000To foster improvements in numerical modelling and predictability based on high quality experimental data, the TUDa-GLR-OpenStage test case is introduced. It comprises a single stage setup, including the BLISK rotor, a 3D-optimized stator as well as the annulus contour. The data set is supplemented with comprehensive measurement data at stage inlet and outlet as well as running tip clearances.\u0000\u0000This paper describes the open test case, related geometries, measurement procedures and corresponding experimental results, including steady state performance and unsteady aerodynamics. Ultimately, it is aiming to provide a standard case for future development of numerical models and comparable validation.","PeriodicalId":53002,"journal":{"name":"Journal of the Global Power and Propulsion Society","volume":" ","pages":""},"PeriodicalIF":0.9,"publicationDate":"2022-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46765016","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}
Silas Mütschard, J. Werner, C. Kunkel, Maximilian Karl, H. Schiffer, C. Biela, Sebastian Robens
In this paper we give insight into characteristics of a 1.5-stage transonic axial compressor rig with focus on surge during a stalled operating point. The new compressor rig at TU Darmstadt is representative for the front stage of an industrial gas turbine. Transient throttling maneuvers were conducted for multiple operating points during the first test campaign of the TCD 2 (Transonic Compressor Darmstadt 2), providing an extensive set of unsteady structural and aerodynamic data beyond the stability limit. Enhanced analytical methods allow detailed studies including aerodynamic spectral analysis as well as determination of propagation speed and size of disturbances. The results differ from observations at comparable test rigs, revealing an interesting manifestation of stall: In a wide range of the stability limit it shows a periodicity. The stall emerges and vanishes recurrently, causing strong oscillations of the pressure ratio. Additional unsteady measurements of the mass flow indicate a surge. Regarding the compressor map, this results in staggering operating points, showing a hysteresis. However, due to a rather small plenum and experience with a similar test rig the TCD 2 was not expected to surge. Comprehensive analyses are carried out to characterize this phenomenon.
{"title":"Investigation of surge in a 1.5-stage transonic axial compressor","authors":"Silas Mütschard, J. Werner, C. Kunkel, Maximilian Karl, H. Schiffer, C. Biela, Sebastian Robens","doi":"10.33737/jgpps/156119","DOIUrl":"https://doi.org/10.33737/jgpps/156119","url":null,"abstract":"In this paper we give insight into characteristics of a 1.5-stage transonic axial compressor rig with focus on surge during a stalled operating point. The new compressor rig at TU Darmstadt is representative for the front stage of an industrial gas turbine. Transient throttling maneuvers were conducted for multiple operating points during the first test campaign of the TCD 2 (Transonic Compressor Darmstadt 2), providing an extensive set of unsteady structural and aerodynamic data beyond the stability limit. Enhanced analytical methods allow detailed studies including aerodynamic spectral analysis as well as determination of propagation speed and size of disturbances. The results differ from observations at comparable test rigs, revealing an interesting manifestation of stall: In a wide range of the stability limit it shows a periodicity. The stall emerges and vanishes recurrently, causing strong oscillations of the pressure ratio. Additional unsteady measurements of the mass flow indicate a surge. Regarding the compressor map, this results in staggering operating points, showing a hysteresis. However, due to a rather small plenum and experience with a similar test rig the TCD 2 was not expected to surge. Comprehensive analyses are carried out to characterize this phenomenon.","PeriodicalId":53002,"journal":{"name":"Journal of the Global Power and Propulsion Society","volume":" ","pages":""},"PeriodicalIF":0.9,"publicationDate":"2022-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47175215","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}
Qing Xie, Siheng Yang, Hao Cheng, Chi Zhang, Zhuyin Ren
Stochastic flame particle tracking in conjunction with non-reacting combustor simulations can offer insights into the ignition processes and facilitate the combustor optimization. In this study, this approach is employed to simulate the ignition sequences in a separated dual-swirl spray flame, in which the newly proposed pairwise mixing-reaction model is used to account for the mass and energy transfer between the flame particle and the surrounding shell layer. Based on the flame particle temperature, the particle state can be classified in to burnt, hot gas, and extinguished. The additional state of hot gas is introduced to allow the flame particles with high temperature to survive from nonflammable region and then potentially to ignite the nearby favourable regions. The simulations of the separated stratified swirl spray flame reveal two different ignition pathways for flame stabilization. The first showed that some flame particles from the spark would directly enter the main recirculation zone resulting from the velocity randomness and then ignite both sides of the combustor simultaneously. The second showed that flame particles from the spark would ignite the traversed regions following the swirl motion inside the combustor. The predicted ignition sequences were compared with the evolution of flame morphology recorded by high-speed imaging from experiments, showing qualitative agreement.
{"title":"Predicting the ignition sequences in a separated stratified swirling spray flame with stochastic flame particle tracking","authors":"Qing Xie, Siheng Yang, Hao Cheng, Chi Zhang, Zhuyin Ren","doi":"10.33737/jgpps/153495","DOIUrl":"https://doi.org/10.33737/jgpps/153495","url":null,"abstract":"Stochastic flame particle tracking in conjunction with non-reacting combustor simulations can offer insights into the ignition processes and facilitate the combustor optimization. In this study, this approach is employed to simulate the ignition sequences in a separated dual-swirl spray flame, in which the newly proposed pairwise mixing-reaction model is used to account for the mass and energy transfer between the flame particle and the surrounding shell layer. Based on the flame particle temperature, the particle state can be classified in to burnt, hot gas, and extinguished. The additional state of hot gas is introduced to allow the flame particles with high temperature to survive from nonflammable region and then potentially to ignite the nearby favourable regions. The simulations of the separated stratified swirl spray flame reveal two different ignition pathways for flame stabilization. The first showed that some flame particles from the spark would directly enter the main recirculation zone resulting from the velocity randomness and then ignite both sides of the combustor simultaneously. The second showed that flame particles from the spark would ignite the traversed regions following the swirl motion inside the combustor. The predicted ignition sequences were compared with the evolution of flame morphology recorded by high-speed imaging from experiments, showing qualitative agreement.","PeriodicalId":53002,"journal":{"name":"Journal of the Global Power and Propulsion Society","volume":" ","pages":""},"PeriodicalIF":0.9,"publicationDate":"2022-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47356915","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}
Nima Fard afshar, D. Kožulović, Stefan Henninger, Johannes Deutsch, P. Bechlars
This study analyzes the flow over a three-dimensional linear low-pressure turbine cascade blade using large eddy simulation at Re = 90,000. The computational model consists of one blade passage with periodic boundaries and synthetic turbulence is generated at the inlet of the domain. Various flow metrics, including isentropic Mach number distribution at mid-span and wake total pressure losses are compared with available experimental data and found to be in good agreement. A more detailed analysis of the turbulence with particular attention to the separation bubble region is subsequently presented. The analysis revealed that the turbulence is in a nearly two-component state very close to the wall region and gradually follows a certain anisotropy trajectory, as the distance from the wall increases. Even in the free-stream region no fully isotropic state is reached, due to large acceleration and flow turning. The results give a new insight into the state of turbulence within the separation region on the blade suction side and emphasize the deficiencies of the Reynolds-averaged Navier Stokes (RANS) turbulence models in reproducing the turbulence anisotropy. This insight is of relevance for the aerodynamic design of turbines, since large parts of the total pressure loss are generated in the separation region.
{"title":"Turbulence anisotropy analysis at the middle section of a highly loaded 3D linear turbine cascade using Large Eddy Simulation","authors":"Nima Fard afshar, D. Kožulović, Stefan Henninger, Johannes Deutsch, P. Bechlars","doi":"10.33737/jgpps/159784","DOIUrl":"https://doi.org/10.33737/jgpps/159784","url":null,"abstract":"This study analyzes the flow over a three-dimensional linear low-pressure turbine cascade blade using large eddy simulation at Re = 90,000. The computational model consists of one blade passage with periodic boundaries and synthetic turbulence is generated at the inlet of the domain. Various flow metrics, including isentropic Mach number distribution at mid-span and wake total pressure losses are compared with available experimental data and found to be in good agreement. A more detailed analysis of the turbulence with particular attention to the separation bubble region is subsequently presented. The analysis revealed that the turbulence is in a nearly two-component state very close to the wall region and gradually follows a certain anisotropy trajectory, as the distance from the wall increases. Even in the free-stream region no fully isotropic state is reached, due to large acceleration and flow turning. The results give a new insight into the state of turbulence within the separation region on the blade suction side and emphasize the deficiencies of the Reynolds-averaged Navier Stokes (RANS) turbulence models in reproducing the turbulence anisotropy. This insight is of relevance for the aerodynamic design of turbines, since large parts of the total pressure loss are generated in the separation region.","PeriodicalId":53002,"journal":{"name":"Journal of the Global Power and Propulsion Society","volume":" ","pages":""},"PeriodicalIF":0.9,"publicationDate":"2022-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45427232","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}
J. Ahrens, Sebastian Kurth, K. Cengiz, Lars Wein, J. Seume
Roughness generally consists of structures that are either oriented anisotropic in directions tangential to the surface or isotropic, or a superposition of both components. Interactions between the roughness elements exert a significant influence on the fluid mechanical losses. Cost-effective maintenance of the functionality of the surfaces of aerodynamically relevant components such as blades requires the quantitative prediction of the influence on the flow, which can be achieved through Reynolds-Averaged-Navier-Stokes Simulations (RANS). An established roughness parameter used to model the influence on the flow is the equivalent sand grain roughness ks. By contrast, the research presented here employs Direct Numerical Simulations (DNS) with Immersed Boundary Method (IBM) of channel flows over anisotropic, isotropic, and superimposed surfaces in order to investigate the aerodynamic losses, for example, due to turbulent production and dissipation. The simulation results show that the equivalent sand grain roughness does not correctly predict flow losses from anisotropic and superimposed surfaces, because in reality, the “angle of attack” with respect to the anisotropic structures changes the turbulence due to altered turbulent production and dissipation. A non-linear relationship between the flow resistance and this angle of attack is a result of local changes in pressure gradients.
{"title":"Investigation of turbulence production and dissipation due to isotropic and anisotropic roughness components on real surfaces","authors":"J. Ahrens, Sebastian Kurth, K. Cengiz, Lars Wein, J. Seume","doi":"10.33737/jgpps/151658","DOIUrl":"https://doi.org/10.33737/jgpps/151658","url":null,"abstract":"Roughness generally consists of structures that are either oriented anisotropic in directions tangential to the surface or isotropic, or a superposition of both components. Interactions between the roughness elements exert a significant influence on the fluid mechanical losses. Cost-effective maintenance of the functionality of the surfaces of aerodynamically relevant components such as blades requires the quantitative prediction of the influence on the flow, which can be achieved through Reynolds-Averaged-Navier-Stokes Simulations (RANS). An established roughness parameter used to model the influence on the flow is the equivalent sand grain roughness ks. By contrast, the research presented here employs Direct Numerical Simulations (DNS) with Immersed Boundary Method (IBM) of channel flows over anisotropic, isotropic, and superimposed surfaces in order to investigate the aerodynamic losses, for example, due to turbulent production and dissipation. The simulation results show that the equivalent sand grain roughness does not correctly predict flow losses from anisotropic and superimposed surfaces, because in reality, the “angle of attack” with respect to the anisotropic structures changes the turbulence due to altered turbulent production and dissipation. A non-linear relationship between the flow resistance and this angle of attack is a result of local changes in pressure gradients.","PeriodicalId":53002,"journal":{"name":"Journal of the Global Power and Propulsion Society","volume":" ","pages":""},"PeriodicalIF":0.9,"publicationDate":"2022-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44223152","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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