Additive manufacturing (AM) allows for the rapid fabrication of complex components relative to conventional fabrication methods aiding in the development and testing of advanced turbine cooling methods. The repeatability of printed geometric features in the same part is required to maintain part quality, flow, and heat transfer. It is widely understood as to the impact that the additional roughness of AM provides with regards to part quality, but part variability also leads to differences in performance either locally in considering a single airfoil or globally when considering an entire stage. Previous studies have shown the importance of certain process parameters, build directions, and feature sizes on the part quality when printing a part using AM. As processes have continued to evolve, other artifacts of AM have arisen such as the location on the build plate. This article highlights the progress that has been made on printing commonly used cooling features by either considering simple straight coupons or a curved vane leading edge. Also discussed is the variability that exists and the resulting convective heat transfer and pressure losses. Results indicate that the variation of roughness between components and the part-to-part variations increased the further the component was from the laser source on the build plate. Similarly, the variation and levels in the pressure loss and heat transfer of the cooling channels also increased when samples were placed further from the laser source on the build plate.
{"title":"Variability in additively manufactured turbine cooling features","authors":"Alexander Wildgoose, K. Thole","doi":"10.33737/jgpps/162654","DOIUrl":"https://doi.org/10.33737/jgpps/162654","url":null,"abstract":"Additive manufacturing (AM) allows for the rapid fabrication of complex components relative to conventional fabrication methods aiding in the development and testing of advanced turbine cooling methods. The repeatability of printed geometric features in the same part is required to maintain part quality, flow, and heat transfer. It is widely understood as to the impact that the additional roughness of AM provides with regards to part quality, but part variability also leads to differences in performance either locally in considering a single airfoil or globally when considering an entire stage. Previous studies have shown the importance of certain process parameters, build directions, and feature sizes on the part quality when printing a part using AM. As processes have continued to evolve, other artifacts of AM have arisen such as the location on the build plate. This article highlights the progress that has been made on printing commonly used cooling features by either considering simple straight coupons or a curved vane leading edge. Also discussed is the variability that exists and the resulting convective heat transfer and pressure losses. Results indicate that the variation of roughness between components and the part-to-part variations increased the further the component was from the laser source on the build plate. Similarly, the variation and levels in the pressure loss and heat transfer of the cooling channels also increased when samples were placed further from the laser source on the build plate.","PeriodicalId":53002,"journal":{"name":"Journal of the Global Power and Propulsion Society","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2023-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46295538","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}
{"title":"Editorial: Some Advances in Additive Manufacturing for Aerothermal Technologies","authors":"Li He","doi":"10.33737/jgpps/168474","DOIUrl":"https://doi.org/10.33737/jgpps/168474","url":null,"abstract":"","PeriodicalId":53002,"journal":{"name":"Journal of the Global Power and Propulsion Society","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2023-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41491243","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 requirements for new generation vehicles in terms of the flight speed, thrust–weight ratio, and maneuverability necessitate the development of high performance and reliable propulsion systems where active thermal protection technology plays a crucial role. Transpiration cooling based on a microporous structure is considered as one of the most promising techniques for protecting the high heat flux walls from ablation in aerospace applications. Unlike conventional fabrication methods, additive manufacturing (AM) has been applied to fabricate three-dimensional (3D) porous structures with customized geometries that are specific to applications, i.e., in terms of the design of features such as the pore diameter, pore density, porosity, and pore morphology. Three major AM technologies (selective laser melting, inkjet, and stereolithography) followed by a post-printing process have been proposed for the additive manufacture of porous structures. In particular, 3D-printed porous structures have great promise for transpiration cooling applications. In this review, we discuss the detailed steps of porous structure topology design and a general framework is presented for AM. The heat transfer and strength performance are also provided for porous parts fabricated by AM. Furthermore, the applications of 3D-printed porous media in transpiration cooling with different regimes are described. This review concludes by explaining the current challenges and prospects for the next generation of 3D-printed porous structures in transpiration cooling systems.
{"title":"Fundamentals and recent progress of additive manufacturing-assisted porous materials on transpiration cooling","authors":"R. Xu, Zhilong Cheng, Peixue Jiang","doi":"10.33737/jgpps/166418","DOIUrl":"https://doi.org/10.33737/jgpps/166418","url":null,"abstract":"The requirements for new generation vehicles in terms of the flight speed, thrust–weight ratio, and maneuverability necessitate the development of high performance and reliable propulsion systems where active thermal protection technology plays a crucial role. Transpiration cooling based on a microporous structure is considered as one of the most promising techniques for protecting the high heat flux walls from ablation in aerospace applications. Unlike conventional fabrication methods, additive manufacturing (AM) has been applied to fabricate three-dimensional (3D) porous structures with customized geometries that are specific to applications, i.e., in terms of the design of features such as the pore diameter, pore density, porosity, and pore morphology. Three major AM technologies (selective laser melting, inkjet, and stereolithography) followed by a post-printing process have been proposed for the additive manufacture of porous structures. In particular, 3D-printed porous structures have great promise for transpiration cooling applications. In this review, we discuss the detailed steps of porous structure topology design and a general framework is presented for AM. The heat transfer and strength performance are also provided for porous parts fabricated by AM. Furthermore, the applications of 3D-printed porous media in transpiration cooling with different regimes are described. This review concludes by explaining the current challenges and prospects for the next generation of 3D-printed porous structures in transpiration cooling systems.","PeriodicalId":53002,"journal":{"name":"Journal of the Global Power and Propulsion Society","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2023-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47920196","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}
Mesh adaptation of unstructured meshes for aerodynamic simulations, that typically resolve the Reynolds Averaged Navier-Stokes (RANS) equations, is a promising approach to enable high numerical precision on complex geometries. Its objective is to minimize the discretization error without using empirical meshing guidelines. The most common approach of mesh adaptation is the “feature-based” isotropic mesh adaptation: from an initial flow prediction on an isotropic unstructured mesh, a local error estimator is computed using a flow variable. It is then used to adapt the mesh using isotropic tetrahedra. Additional near-wall resolution can be achieved by extruding prism layers from the walls. A more efficient approach is to use anisotropic mesh adaptation purely with tetrahedra that are stretched to follow the flow's preferential directions. In this work, we demonstrate the abilities of feature-based isotropic and anisotropic mesh adaptation on a complex flow phenomenon of importance for jet engines: flow separation in a nacelle under crosswind conditions. Two different solvers, adapted for either isotropic or anisotropic meshes, are employed. Results are compared with standard unstructured simulations with user-imposed mesh refinements and highlight the ability of mesh adaptation to automatically capture all the relevant flow phenomena without any user input and at reduced mesh size.
{"title":"Isotropic and anisotropic mesh adaptation for RANS simulations of a nacelle under crosswind conditions","authors":"Billon Laure, Papadogiannis Dimitrios, Alauzet Frédéric","doi":"10.33737/jgpps/162640","DOIUrl":"https://doi.org/10.33737/jgpps/162640","url":null,"abstract":"Mesh adaptation of unstructured meshes for aerodynamic simulations, that typically resolve the Reynolds Averaged Navier-Stokes (RANS) equations, is a promising approach to enable high numerical precision on complex geometries. Its objective is to minimize the discretization error without using empirical meshing guidelines. The most common approach of mesh adaptation is the “feature-based” isotropic mesh adaptation: from an initial flow prediction on an isotropic unstructured mesh, a local error estimator is computed using a flow variable. It is then used to adapt the mesh using isotropic tetrahedra. Additional near-wall resolution can be achieved by extruding prism layers from the walls. A more efficient approach is to use anisotropic mesh adaptation purely with tetrahedra that are stretched to follow the flow's preferential directions. In this work, we demonstrate the abilities of feature-based isotropic and anisotropic mesh adaptation on a complex flow phenomenon of importance for jet engines: flow separation in a nacelle under crosswind conditions. Two different solvers, adapted for either isotropic or anisotropic meshes, are employed. Results are compared with standard unstructured simulations with user-imposed mesh refinements and highlight the ability of mesh adaptation to automatically capture all the relevant flow phenomena without any user input and at reduced mesh size.","PeriodicalId":53002,"journal":{"name":"Journal of the Global Power and Propulsion Society","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2023-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48263387","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}
Dogan Bicat, Katharina Stichling, Maximilian Elfner, Hans-Jörg Bauer, Knut Lehmann
Cyclone cooling is a promising method for a more effective internal cooling of turbine rotor blades with simplified internal channels including a swirling flow to enhance internal heat transfer. Previous studies have led to the conclusion that improving the cooling performance requires an adapted film cooling design, tailored to the cyclone cooling application. In this paper, a turbine rotor blade with realistic, complex features including the cyclone cooling design is investigated experimentally using infrared thermography to capture surface temperature. The objective is to analyze the influence of increased film cooling hole diameter on a cyclone-cooled blade’s surface temperature. For this purpose, the diameter of the holes at the blade’s leading edge, which are fed by the cyclone channel, is increased. The tests are performed for different coolant mass flow rates and swirl numbers. Additionally, CFD simulations are performed to analyze the aerodynamics of the cooling air. The test results show that the surface temperature at the leading edge can be decreased by increasing the diameter of the film cooling holes, however, adversely affecting the remaining blade surface. This can be explained by a redistribution of the supplied coolant. The increase of cooling effectiveness at the leading edge is at the highest when a low swirl is generated.
{"title":"Experimental investigation of the influence of film cooling hole diameter on the total cooling effectiveness for cyclone-cooled turbine blades","authors":"Dogan Bicat, Katharina Stichling, Maximilian Elfner, Hans-Jörg Bauer, Knut Lehmann","doi":"10.33737/jgpps/165825","DOIUrl":"https://doi.org/10.33737/jgpps/165825","url":null,"abstract":"Cyclone cooling is a promising method for a more effective internal cooling of turbine rotor blades with simplified internal channels including a swirling flow to enhance internal heat transfer. Previous studies have led to the conclusion that improving the cooling performance requires an adapted film cooling design, tailored to the cyclone cooling application. In this paper, a turbine rotor blade with realistic, complex features including the cyclone cooling design is investigated experimentally using infrared thermography to capture surface temperature. The objective is to analyze the influence of increased film cooling hole diameter on a cyclone-cooled blade’s surface temperature. For this purpose, the diameter of the holes at the blade’s leading edge, which are fed by the cyclone channel, is increased. The tests are performed for different coolant mass flow rates and swirl numbers. Additionally, CFD simulations are performed to analyze the aerodynamics of the cooling air. The test results show that the surface temperature at the leading edge can be decreased by increasing the diameter of the film cooling holes, however, adversely affecting the remaining blade surface. This can be explained by a redistribution of the supplied coolant. The increase of cooling effectiveness at the leading edge is at the highest when a low swirl is generated.","PeriodicalId":53002,"journal":{"name":"Journal of the Global Power and Propulsion Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136016017","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}
Sebastian Kurth, Cengiz Kenan, Moeller Daniel, Wein Lars, J. Seume
In recent years, the research on roughness has focused on various roughness features, rather than the roughness height only, in order to improve the understanding of roughness effects on wall bounded flows. A special focus is placed on the skewness of the roughness height profile. The skewness measures whether the height profile is dominated by negative or positive roughness elements. Surfaces with both features can be found on worn blades: On the leading edge, roughness is caused by the impact of particles resulting in a negative skewness. Rough surfaces around the trailing edge, however, develop due to depositions leading to a positive skewness. In this paper, rough surfaces taken from a compressor blade of an aero engine are systematically varied to investigate the isolated effect of skewness on aerodynamic losses. By direct numerical simulations of a periodic flow channel. The results show that the skewness has a major influence on loss generation. Based on these results, an existing model which essentially uses the shape-and-density parameter, is extended by a skewness factor. The modified correlation predicts the influence of the rough surfaces investigated well.
{"title":"Systematic roughness variation to model the influence of skewness on wall bounded flows","authors":"Sebastian Kurth, Cengiz Kenan, Moeller Daniel, Wein Lars, J. Seume","doi":"10.33737/jgpps/163089","DOIUrl":"https://doi.org/10.33737/jgpps/163089","url":null,"abstract":"In recent years, the research on roughness has focused on various roughness features, rather than the roughness height only, in order to improve the understanding of roughness effects on wall bounded flows. A special focus is placed on the skewness of the roughness height profile. The skewness measures whether the height profile is dominated by negative or positive roughness elements. Surfaces with both features can be found on worn blades: On the leading edge, roughness is caused by the impact of particles resulting in a negative skewness. Rough surfaces around the trailing edge, however, develop due to depositions leading to a positive skewness.\u0000\u0000In this paper, rough surfaces taken from a compressor blade of an aero engine are systematically varied to investigate the isolated effect of skewness on aerodynamic losses. By direct numerical simulations of a periodic flow channel. The results show that the skewness has a major influence on loss generation. Based on these results, an existing model which essentially uses the shape-and-density parameter, is extended by a skewness factor. The modified correlation predicts the influence of the rough surfaces investigated well.","PeriodicalId":53002,"journal":{"name":"Journal of the Global Power and Propulsion Society","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2023-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48242461","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}
Daniele Cirigliano, Herol Lawerence D'Souza, Felix Grimm, Peter Kutne, Manfred Aigner
Micro Gas Turbines (MGTs) are nowadays largely used for electrical and thermal energy production in small buildings and households. Their reliability and compactness allow them to operate for thousands of hours with minimal maintenance. However, the long exposure at high temperatures in combustion chambers can promote creep, which can induce thermal fatigue and potential failure of these components. Creep-induced damage in MGTs has not yet been thoroughly investigated, due to the lack of numerical tools able to model these strongly coupled phenomena. This study presents the development of a Fortran-based subroutine integrated into ANSYS APDL. The code allows for a life assessment based on the Lemaitre-Chaboche creep damage model. Secondary creep and stress relaxation are modeled for the high-temperature resistant alloy Inconel718. A new set of temperature-dependent parameters for the Norton equation is provided, and the method to obtain these parameters from creep rupture tests is outlined. The model is validated and shows good agreement with experimental data. The subroutine correctly reproduces visco-plasticity, stress relaxation and damage under typical MGTs operating temperatures. This model constitutes the foundation of a life-assessment analysis for combustion chambers. The results highlight the impact of temperature and creep on the component’s life and the importance of integrating life assessment analysis into the preliminary design of combustion chambers.
{"title":"Creep-damage modelling for micro gas turbine combustion chambers lifetime prediction","authors":"Daniele Cirigliano, Herol Lawerence D'Souza, Felix Grimm, Peter Kutne, Manfred Aigner","doi":"10.33737/jgpps/163088","DOIUrl":"https://doi.org/10.33737/jgpps/163088","url":null,"abstract":"Micro Gas Turbines (MGTs) are nowadays largely used for electrical and thermal energy production in small buildings and households. Their reliability and compactness allow them to operate for thousands of hours with minimal maintenance. However, the long exposure at high temperatures in combustion chambers can promote creep, which can induce thermal fatigue and potential failure of these components. Creep-induced damage in MGTs has not yet been thoroughly investigated, due to the lack of numerical tools able to model these strongly coupled phenomena. This study presents the development of a Fortran-based subroutine integrated into ANSYS APDL. The code allows for a life assessment based on the Lemaitre-Chaboche creep damage model. Secondary creep and stress relaxation are modeled for the high-temperature resistant alloy Inconel718. A new set of temperature-dependent parameters for the Norton equation is provided, and the method to obtain these parameters from creep rupture tests is outlined. The model is validated and shows good agreement with experimental data. The subroutine correctly reproduces visco-plasticity, stress relaxation and damage under typical MGTs operating temperatures. This model constitutes the foundation of a life-assessment analysis for combustion chambers. The results highlight the impact of temperature and creep on the component’s life and the importance of integrating life assessment analysis into the preliminary design of combustion chambers.","PeriodicalId":53002,"journal":{"name":"Journal of the Global Power and Propulsion Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135158644","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}
Lukas Schäflein, Johannes Janssen, Henri Brandies, Peter Jeschke, Stephan Behre
This paper presents an investigation of the aerodynamic influence of rim seal purge flow injection on the main flow in a 1.5-stage turbine with non-axisymmetric end walls and a bowed stator using experimental flow measurements and unsteady RANS simulations. The study focuses on the secondary vortex structures formed in the rotor passages of the 1.5-stage axial turbine rig. Through performance map measurements, it was found that the efficiency gain of the non-axisymmetric configuration is partially eliminated by the injection of purge flow. Numerical investigations, which are supported by detailed flow measurements with five-hole probes and hot-wire probes, revealed that the injection of purge air flow intensifies vortex structures near the hub, thereby generating additional losses. These resulting vortex structures are highly similar both in the axisymmetric baseline and the non-axisymmetric configuration and are the result of jet-like vortices emerging from the cavity. From these findings, it can be concluded that the non-axisymmetric contour and the bowed stator no longer provides any efficiency benefit near the hub. Only the near the casing, where the flow is not affected by the purge flow, the optimized configuration continues to improve the efficiency of the rig by homogenizing the stator outflow and thus reducing the secondary flow structures in the rotor passages.
{"title":"Aerodynamic influence of rim seal purge flow injection on the main flow in a 1.5-stage axial turbine with nonaxisymmetric end wall contouring","authors":"Lukas Schäflein, Johannes Janssen, Henri Brandies, Peter Jeschke, Stephan Behre","doi":"10.33737/jgpps/162078","DOIUrl":"https://doi.org/10.33737/jgpps/162078","url":null,"abstract":"This paper presents an investigation of the aerodynamic influence of rim seal purge flow injection on the main flow in a 1.5-stage turbine with non-axisymmetric end walls and a bowed stator using experimental flow measurements and unsteady RANS simulations. The study focuses on the secondary vortex structures formed in the rotor passages of the 1.5-stage axial turbine rig. Through performance map measurements, it was found that the efficiency gain of the non-axisymmetric configuration is partially eliminated by the injection of purge flow. Numerical investigations, which are supported by detailed flow measurements with five-hole probes and hot-wire probes, revealed that the injection of purge air flow intensifies vortex structures near the hub, thereby generating additional losses. These resulting vortex structures are highly similar both in the axisymmetric baseline and the non-axisymmetric configuration and are the result of jet-like vortices emerging from the cavity. From these findings, it can be concluded that the non-axisymmetric contour and the bowed stator no longer provides any efficiency benefit near the hub. Only the near the casing, where the flow is not affected by the purge flow, the optimized configuration continues to improve the efficiency of the rig by homogenizing the stator outflow and thus reducing the secondary flow structures in the rotor passages.","PeriodicalId":53002,"journal":{"name":"Journal of the Global Power and Propulsion Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136001579","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}
Lukas Schwerdt, N. Maroldt, Lars Panning‐von Scheidt, J. Wallaschek, J. Seume
To assess the influence of mistuning on the vibration amplitudes of turbomachinery rotors, reduced order models (ROMs) are widely used. A variety of methods are available for single-stage configurations and mostly aeroelastic effects can be taken into account. More recent research focusses on extending these methods to include multiple stages. However, due to the significantly increased computational effort of the aeroelastic simulations when adding more stages to the models, these ROMs are rarely applied with the inclusion of multistage aeroelastic effects. It is therefore desirable to develop reduction methods which minimize the number of these simulations to reduce the computational cost and thereby enable analyses of rotors with multiple stages including aeroelastic effects. In this paper, a cyclic Craig-Bampton reduction method with an a priori interface reduction for multistage rotors is extended with an additional a posteriori interface reduction to reduce the number of aeroelastic simulations necessary for a given accuracy level of the ROM. The interface degrees of freedom between stages are reduced using a modified version of Characteristic Constraint Modes, to yield a more efficient representation of their displacements while retaining their monoharmonic nature. The method is applied to a two-stage axial compressor with full aeroelastic coupling between the stages and its reduced computational effort is demonstrated. Additionally, two sorting methods for the degrees of freedom (DOFs) of the ROM are compared.
{"title":"An improved reduced order model for bladed disks including multistage aeroelastic and structural coupling","authors":"Lukas Schwerdt, N. Maroldt, Lars Panning‐von Scheidt, J. Wallaschek, J. Seume","doi":"10.33737/jgpps/161707","DOIUrl":"https://doi.org/10.33737/jgpps/161707","url":null,"abstract":"To assess the influence of mistuning on the vibration amplitudes of turbomachinery rotors, reduced order models (ROMs) are widely used. A variety of methods are available for single-stage configurations and mostly aeroelastic effects can be taken into account. More recent research focusses on extending these methods to include multiple stages. However, due to the significantly increased computational effort of the aeroelastic simulations when adding more stages to the models, these ROMs are rarely applied with the inclusion of multistage aeroelastic effects. It is therefore desirable to develop reduction methods which minimize the number of these simulations to reduce the computational cost and thereby enable analyses of rotors with multiple stages including aeroelastic effects. In this paper, a cyclic Craig-Bampton reduction method with an a priori interface reduction for multistage rotors is extended with an additional a posteriori interface reduction to reduce the number of aeroelastic simulations necessary for a given accuracy level of the ROM. The interface degrees of freedom between stages are reduced using a modified version of Characteristic Constraint Modes, to yield a more efficient representation of their displacements while retaining their monoharmonic nature. The method is applied to a two-stage axial compressor with full aeroelastic coupling between the stages and its reduced computational effort is demonstrated. Additionally, two sorting methods for the degrees of freedom (DOFs) of the ROM are compared.","PeriodicalId":53002,"journal":{"name":"Journal of the Global Power and Propulsion Society","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2023-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47607149","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}
Variable pitch low pressure ratio fans could enable higher propulsive efficiency and eliminate the need for heavy thrust reversers. In this paper, the effects of the fan rotor design on reverse thrust capability have been explored by varying key parameters of NASA’s Advanced Ducted Propulsor (ADP) while maintaining cruise point performance. Reverse thrust performance has been assessed using RANS single passage CFD of the variable pitch fan system with an extended domain. This computational approach has been validated using NASA Stage 51B, an experimental variable pitch fan test case. Predicted total pressure and total pressure ratios for this case were found to agree with test data within experimental error, except where large tip region separations occurred at high incidence. Applying individual variations to rotor pitch-to-chord, radial loading distribution, and chordwise camber distribution generated changes to rotor incidence, blockage, and peak surface Mach numbers in reverse operation. An increase in gross reverse thrust of up to 8% was achieved through reductions in rotor pitch-to-chord due to improved loading and lower shock Mach numbers. Controlling section camber distributions was used to move the rotor shock downstream and was found to increase reverse thrust by up to 3%. Increasing rotor loading at the mid span relative to the tip resulted in high tip incidence and a 50% reduction in gross reverse thrust across all rotor speeds. This suggests that tip loaded designs are required for high levels of reverse thrust.
{"title":"Variable pitch fan aerodynamic design for reverse thrust operation","authors":"Tim Williams, Cesare Hall, Mark Wilson","doi":"10.33737/jgpps/160096","DOIUrl":"https://doi.org/10.33737/jgpps/160096","url":null,"abstract":"Variable pitch low pressure ratio fans could enable higher propulsive efficiency and eliminate the need for heavy thrust reversers. In this paper, the effects of the fan rotor design on reverse thrust capability have been explored by varying key parameters of NASA’s Advanced Ducted Propulsor (ADP) while maintaining cruise point performance. Reverse thrust performance has been assessed using RANS single passage CFD of the variable pitch fan system with an extended domain. This computational approach has been validated using NASA Stage 51B, an experimental variable pitch fan test case. Predicted total pressure and total pressure ratios for this case were found to agree with test data within experimental error, except where large tip region separations occurred at high incidence. Applying individual variations to rotor pitch-to-chord, radial loading distribution, and chordwise camber distribution generated changes to rotor incidence, blockage, and peak surface Mach numbers in reverse operation. An increase in gross reverse thrust of up to 8% was achieved through reductions in rotor pitch-to-chord due to improved loading and lower shock Mach numbers. Controlling section camber distributions was used to move the rotor shock downstream and was found to increase reverse thrust by up to 3%. Increasing rotor loading at the mid span relative to the tip resulted in high tip incidence and a 50% reduction in gross reverse thrust across all rotor speeds. This suggests that tip loaded designs are required for high levels of reverse thrust.","PeriodicalId":53002,"journal":{"name":"Journal of the Global Power and Propulsion Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135742547","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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