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":null,"pages":null},"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":null,"pages":null},"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":null,"pages":null},"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":null,"pages":null},"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":null,"pages":null},"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":null,"pages":null},"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}
In this work we examine the flow deviation and its relationship to critical choking, i.e., choking of the meridional component of velocity, in transonic turbine cascades operating with non-ideal compressible flows. To this purpose, a generalized expression of the corrected flow per unit area as a function of both the thermodynamic state and the molecular complexity of the working fluid, the Mach number, and the amount of swirl is derived. The trends of the corrected flow with respect to these quantities are used to infer physical insights on the flow deviation and on the operability of transonic turbine cascades in off-design conditions. Moreover, reduced-order models for the estimation of the flow deviation and the preliminary assessment of the losses have been developed and validated against the results of CFD simulations performed on a representative transonic turbine stator. Results suggest that flows of dense organic vapors exhibit larger deviations than those pertaining to compounds made of simple molecules, e.g., air. Furthermore, transonic turbines expanding dense vapors reach critical choking conditions at lower Mach numbers than the ones operating with simple molecules, and are affected by larger dissipation due to viscous mixing.
{"title":"Flow deviation and critical choking in transonic turbine cascades operating with non-ideal compressible flows","authors":"Francesco Tosto, A. Giuffrè, P. Colonna, M. Pini","doi":"10.33737/jgpps/151659","DOIUrl":"https://doi.org/10.33737/jgpps/151659","url":null,"abstract":"In this work we examine the flow deviation and its relationship to critical choking, i.e., choking of the meridional component of velocity, in transonic turbine cascades operating with non-ideal compressible flows. To this purpose, a generalized expression of the corrected flow per unit area as a function of both the thermodynamic state and the molecular complexity of the working fluid, the Mach number, and the amount of swirl is derived. The trends of the corrected flow with respect to these quantities are used to infer physical insights on the flow deviation and on the operability of transonic turbine cascades in off-design conditions. Moreover, reduced-order models for the estimation of the flow deviation and the preliminary assessment of the losses have been developed and validated against the results of CFD simulations performed on a representative transonic turbine stator. Results suggest that flows of dense organic vapors exhibit larger deviations than those pertaining to compounds made of simple molecules, e.g., air. Furthermore, transonic turbines expanding dense vapors reach critical choking conditions at lower Mach numbers than the ones operating with simple molecules, and are affected by larger dissipation due to viscous mixing.","PeriodicalId":53002,"journal":{"name":"Journal of the Global Power and Propulsion Society","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2022-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42906361","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}
Jiajun Cao, Qingbiao Li, Liping Xu, Rui Yang, Yuejin Dai
Current surrogate model methods that are widely used in optimization and design processes rely on manual parameterization to describe the geometry of objects. The loss of geometric information in this process limits the prediction accuracy of surrogate model. To tackle this problem, the new method directly picks important geometric features from surface meshes of fluid domain using Graph Neural Networks (GNNs) and predicts contours of fluid variables based on extracted information with Convolutional Neural Networks (CNNs). The prediction error of CNNs propagates backwards to train GNNs to select sensitive features from surface meshes. This framework reduces uncertainties introduced by manual parameterization and the loss of geometric information because the input of this new method is from the meshes used in the numerical simulations. With CNN and larger amount of extracted geometric information, this method can also predict higher dimensions distributions of flow variables rather than only several performance metrics. The nature of non-parametric representation of geometry also allows users to access designs defined by other parameterization methods to create a larger database. Additionally, thanks to the generic nature of the new method, it can be used for any other design or optimization processes governed by partial differential equations involving complicated geometries. To demonstrate this new method, a non-parametric surrogate model is built for a low-pressure steam turbine exhaust system (LPES). The new surrogate model uses 10 surfaces meshes of the LPES as input and it is used to predicts the energy flux contours at the exit of the last stage of the turbine. Altogether 582 designs have been generated, which contains two types of geometries defined by different methods. Among them, 550 cases are used for training, and 32 cases for testing. The power output of the last two stages of the turbine predicted by the surrogate model has average 0.86% difference compared with those of numerical simulations over a wide range of power ratings. The structural similarity index measure (SSIM) is used to measure the differences between the simulated and predicted contours at the exit of the last rotor, where the average SSIM of 640 contours is 0.9594 (1.0 being identical).
{"title":"Non-parametric surrogate model method based on machine learning with application on low-pressure steam turbine exhaust system","authors":"Jiajun Cao, Qingbiao Li, Liping Xu, Rui Yang, Yuejin Dai","doi":"10.33737/jgpps/151661","DOIUrl":"https://doi.org/10.33737/jgpps/151661","url":null,"abstract":"Current surrogate model methods that are widely used in optimization and design processes rely on manual parameterization to describe the geometry of objects. The loss of geometric information in this process limits the prediction accuracy of surrogate model. To tackle this problem, the new method directly picks important geometric features from surface meshes of fluid domain using Graph Neural Networks (GNNs) and predicts contours of fluid variables based on extracted information with Convolutional Neural Networks (CNNs). The prediction error of CNNs propagates backwards to train GNNs to select sensitive features from surface meshes. This framework reduces uncertainties introduced by manual parameterization and the loss of geometric information because the input of this new method is from the meshes used in the numerical simulations. With CNN and larger amount of extracted geometric information, this method can also predict higher dimensions distributions of flow variables rather than only several performance metrics. The nature of non-parametric representation of geometry also allows users to access designs defined by other parameterization methods to create a larger database. Additionally, thanks to the generic nature of the new method, it can be used for any other design or optimization processes governed by partial differential equations involving complicated geometries. To demonstrate this new method, a non-parametric surrogate model is built for a low-pressure steam turbine exhaust system (LPES). The new surrogate model uses 10 surfaces meshes of the LPES as input and it is used to predicts the energy flux contours at the exit of the last stage of the turbine. Altogether 582 designs have been generated, which contains two types of geometries defined by different methods. Among them, 550 cases are used for training, and 32 cases for testing. The power output of the last two stages of the turbine predicted by the surrogate model has average 0.86% difference compared with those of numerical simulations over a wide range of power ratings. The structural similarity index measure (SSIM) is used to measure the differences between the simulated and predicted contours at the exit of the last rotor, where the average SSIM of 640 contours is 0.9594 (1.0 being identical).","PeriodicalId":53002,"journal":{"name":"Journal of the Global Power and Propulsion Society","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2022-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48020678","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 drastic property changes of supercritical CO2 (SCO2) make the performance of SCO2 compressors different from that of conventional compressors. This study deals with the real-gas effect on the SCO2 compressor performance by theoretical analysis and numerical validation. A set of similitude parameters are firstly deduced by dimensional analysis. Then keeping these parameters unchanged, the performance variation of a SCO2 compressor is analyzed when the inlet flow condition changes in a certain temperature and pressure range. Results show that the proposed similitude method could accurately reflect the variation trend of SCO2 compressor performance under different inflow conditions. The real-gas effect enables the compressor to obtain higher pressure ratio with lower temperature rise. It is recommended that the inlet temperature of SCO2 compressor should be as close as possible to the critical temperature and the pressure should be about 150 kPa higher than the corresponding pseudo-critical pressure at the same temperature.
{"title":"A study of real-gas effect on SCO2 compressor performance using similitude method","authors":"Pengcheng Xu, Z. Zou","doi":"10.33737/jgpps/152462","DOIUrl":"https://doi.org/10.33737/jgpps/152462","url":null,"abstract":"The drastic property changes of supercritical CO2 (SCO2) make the performance of SCO2 compressors different from that of conventional compressors. This study deals with the real-gas effect on the SCO2 compressor performance by theoretical analysis and numerical validation. A set of similitude parameters are firstly deduced by dimensional analysis. Then keeping these parameters unchanged, the performance variation of a SCO2 compressor is analyzed when the inlet flow condition changes in a certain temperature and pressure range. Results show that the proposed similitude method could accurately reflect the variation trend of SCO2 compressor performance under different inflow conditions. The real-gas effect enables the compressor to obtain higher pressure ratio with lower temperature rise. It is recommended that the inlet temperature of SCO2 compressor should be as close as possible to the critical temperature and the pressure should be about 150 kPa higher than the corresponding pseudo-critical pressure at the same temperature.","PeriodicalId":53002,"journal":{"name":"Journal of the Global Power and Propulsion Society","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2022-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47851531","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}
A. Gaitanis, Antoine Laterre, F. Contino, W. De Paepe
In an energy mix driven by renewables, there is a need for small-scale highly efficient and flexible cogeneration units, such as Micro Gas Turbines (mGTs). These mGTs should perform transient operations and work at part-load to meet the power grid requirements. Therefore, full transient characterisation is necessary. One of the most crucial factors is accurately incorporating each component's dynamic behavior. Compressor and Turbine performance maps, although essential, are usually obtained in costly test rigs or CFD simulations. Also, the accurate modelling of the heat exchanger affects the efficiency of the whole cycle. The aim of this work is the development of real time transient mGT model, where we focus in the first step on accurate component modelling. Hence, an effective performance map representation method for mGT's compressor and turbine was developed. Moreover, a Recuperator 1-D numerical model is developed. Those modelling techniques were tested in a MATLAB/SIMULINK model in transient conditions. The fundamental target of this study is to enhance the fidelity of dynamic simulations for small-scale gas turbines. Key parameters like shaft speed and combustor inlet temperature, show deviation from experiments less than 1% which solidifies our aim to establish a general and efficient performance prediction.
{"title":"Towards real time transient mGT performance assessment: effective prediction using accurate component modelling techniques","authors":"A. Gaitanis, Antoine Laterre, F. Contino, W. De Paepe","doi":"10.33737/jgpps/150359","DOIUrl":"https://doi.org/10.33737/jgpps/150359","url":null,"abstract":"In an energy mix driven by renewables, there is a need for small-scale highly efficient and flexible cogeneration units, such as Micro Gas Turbines (mGTs). These mGTs should perform transient operations and work at part-load to meet the power grid requirements. Therefore, full transient characterisation is necessary. One of the most crucial factors is accurately incorporating each component's dynamic behavior. Compressor and Turbine performance maps, although essential, are usually obtained in costly test rigs or CFD simulations. Also, the accurate modelling of the heat exchanger affects the efficiency of the whole cycle. The aim of this work is the development of real time transient mGT model, where we focus in the first step on accurate component modelling. Hence, an effective performance map representation method for mGT's compressor and turbine was developed. Moreover, a Recuperator 1-D numerical model is developed. Those modelling techniques were tested in a MATLAB/SIMULINK model in transient conditions. The fundamental target of this study is to enhance the fidelity of dynamic simulations for small-scale gas turbines. Key parameters like shaft speed and combustor inlet temperature, show deviation from experiments less than 1% which solidifies our aim to establish a general and efficient performance prediction.","PeriodicalId":53002,"journal":{"name":"Journal of the Global Power and Propulsion Society","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2022-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42493671","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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