The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Xin Qian Zheng - One of the best experts on this subject based on the ideXlab platform.
-
stability improvement of a high Pressure Ratio centrifugal compressor by flow injection
Journal of Aerospace Engineering, 2020Co-Authors: Wenchao Zhang, Baotong Wang, Zhenzhong Sun, Xin Qian ZhengAbstract:AbstractHigh-Pressure Ratio centrifugal compressors are required in modern turboshaft engines with the requirements of a high power-to-weight Ratio and low fuel consumption. The reduction of the st...
-
roles and mechanisms of casing treatment on different scales of flow instability in high Pressure Ratio centrifugal compressors
Aerospace Science and Technology, 2019Co-Authors: Xin Qian ZhengAbstract:Abstract The development of single-stage high Pressure Ratio centrifugal compressors for small gas turbine engines is hindered by compressor flow instabilities with various temporal and spatial scales. In this paper, the effect of a self-recirculation casing treatment device for suppressing various scales of flow instability has been discussed. Rig tests of a high Pressure Ratio centrifugal compressor with and without a casing treatment device are performed, and transient Pressure signals are measured at endwalls by fast response Pressure transducers. By analyzing measured Pressure signals in both time and frequency domain, the casing treatment device is found effective in eliminating rotating instability and stall at the impeller inlet at low speeds, as well as suppressing surge of the compression system at middle and high speeds. The flow recirculation process generated inside the casing treatment device removes the vortical structures at the impeller inlet tip section, therefore eliminating the regional rotating instability and stall. Besides, the casing treatment device turns the Pressure rise characteristics of the impeller more negative by enhancing the impeller work input, but turns that of the vaned diffuser more positive by increasing the incidence at the vaned diffuser inlet. Combining both effects, mild surge and the deep surge are suppressed.
-
flow instability evolution in high Pressure Ratio centrifugal compressor with vaned diffuser
Experimental Thermal and Fluid Science, 2018Co-Authors: Xiao He, Xin Qian ZhengAbstract:Abstract Compressor stability is an essential issue for developing single-stage high Pressure Ratio centrifugal compressors. In this paper, a comprehensive stability map of a centrifugal compressor stage with the peak Pressure Ratio of 6.2 has been illustrated. Fast response Pressure transducers are mounted inside the casing or the back-plate wall to measure internal transient behaviors. From Fourier analysis of Pressure signals, various instabilities across time and length scales are identified. At low speeds, the impeller inlet rotating instability develops in scale and evolves into the inducer stall, which eventually induces the mild surge and deep surge of the compression system. At middle speeds, the compressor successively experiences stable state, mild surge, rotating instability, and deep surge. The mild surge region coincides with the dip region of the compressor S-shape Pressure rise curve, and deep surge occurs when the compressor Pressure rise raises to the second peak. At high speeds, mild surge and deep surge abruptly occur without preceding stall or rotating instability. To explain the complex surge behavior, the mechanical analogy between the compression system and the mass-spring-damper system is applied. Both mild surge and deep surge transients are found to belong to the dynamic instability of the mass-spring-damper system, and the exact form of the surge state will be determined by eigenvalues of the system governing equation.
-
effects of variable diffuser vanes on performance of a centrifugal compressor with Pressure Ratio of 8 0
Energies, 2017Co-Authors: Mohsen Ebrahimi, Qiangqiang Huang, Xin Qian ZhengAbstract:In numerous applications, centrifugal compressors are required to provide a high Pressure Ratio with good efficiency while also working in a wide operating range. This is a challenge because as Pressure Ratio increases, efficiency and operating range inevitably decline. This paper studies the effects of a variable geometry diffuser on the performance and operating range of a centrifugal compressor with high Pressure Ratios of up to 8.0. The numerical method employed three-dimensional Reynolds-averaged Navier-Stokes simulations. An analysis of the matching of the vaned diffuser with the impeller for different working conditions and diffuser vane angles is presented. The results show that improved matching of the adjusted diffuser increased efficiency by 4.5%. The range extension mechanism of the variable diffuser is explained, and it is shown that adjusting the vane angle by +6° to −6° extended the operating range of the compressor by up to 30.0% for Pressure Ratios between 5.0 and 6.0. The interaction between diffuser and impeller was examined, and the independent characteristic of the impeller is illustrated. The connection between the incidence angle at the leading edge of the impeller and flow sepaRation near the tip of the impeller is discussed.
-
Effect of internal heat leakage on the performance of a high Pressure Ratio centrifugal compressor
Applied Thermal Engineering, 2017Co-Authors: S M Moosania, Xin Qian ZhengAbstract:Centrifugal compressors are widely used in compact gas turbines in industrial and military applications where a high Pressure Ratio in small size is needed. The trend in centrifugal compressor is high Pressure Ratios and high efficiencies. However, higher Pressure Ratio increases the temperature difference between upstream flow and downstream flow which leads to a heat leakage from downstream to upstream through the solid parts. This heat leakage negatively affects the performance as well as the reliability of the compressor. In this study the effect of heat leakage through solid impeller and casing on the compressor performance has been studied for different Pressure Ratios. The compressor performance has been calculated using a three dimensional numerical model. Conjugate Heat Transfer (CHT) method has been used to calculate the temperature in the solid parts. The results show that the internal heat leakage through both the impeller and casing reduces the efficiency by 2.5% and the total Pressure Ratio by about 0.83 at Pressure Ratio up to 11. The effect of the internal heat transfer on the compressor performance is more noticeable at Pressure Ratios higher than 5. Meanwhile, heat transfer inside the solid impeller alone from the hot region to the cool region reduces the maximum impeller temperature while this heat leakage has a small effect on the compressor performance. However, heat leakage inside the casing alone slightly increases the impeller temperature while it strongly affects the compressor performance.
Mingyang Yang - One of the best experts on this subject based on the ideXlab platform.
-
inlet duct treatment for stability improvement on a high Pressure Ratio centrifugal compressor
ASME Turbo Expo 2013: Turbine Technical Conference and Exposition, 2013Co-Authors: Mingyang Yang, Ricardo Martinezbotas, Yangjun ZhangAbstract:The operating range of a centrifugal compressor, determined by surge and choke flow rate, is a key issue for turbocharging since a vehicle internal combustion engine (ICE) is usually operated across a wide range. In this paper a new flow control method is developed and validated numerically, in which an array of circumferentially distributed holes is designed in the inner wall of the inlet duct of a high Pressure Ratio centrifugal compressor of a turbocharger. Firstly the numerical method is validated by experimental results of the original turbocharging centrifugal compressor with a Pressure Ratio of 4. Next the validated method is used to investigate the new flow control method and its effect on the compressor’s performance. Results show that the method can enhance the compressor stability and widen the operating range effectively at all investigated speeds. At meantime, the choke flow reduces slightly. The flow details in the compressor are further analysed according to the CFD results. It is found that the flow near the blade tip at inlet is pre-swirled by the method as the conventional IGV does while the flow in the middle span or near the hub remains in an axial direction. As a result, the stability of the compressor is enhanced by the pre-swirl effect at the tip while minimally sacrificing the choke flow rate, thus the map is extended effectively by the flow control method.Copyright © 2013 by ASME
-
stability improvement of high Pressure Ratio turbocharger centrifugal compressor by asymmetric flow control part i non axisymmetrical flow in centrifugal compressor
Journal of Turbomachinery-transactions of The Asme, 2013Co-Authors: Mingyang Yang, Xin Qian Zheng, Joern Huenteler, Takeshi Bamba, Hideaki Tamaki, Yangjun Zhang, Zhigang LiAbstract:The history of turbocharging is almost as old as that of the internal combustion engine. A turbocharger consists of a compressor and a turbine. The compressor is driven by the turbine extracting energy from exhaust gases. Compared to a naturally aspirated engine, the benefits of a turbocharged engine are increased power, lower fuel consumption, and reduced emissions [1,2]. High-Pressure-Ratio turbocharging technology is the developing trend of turbocharged internal combustion engines due to the following reasons: 1) significant downsizing to mitigate CO2 emission and reduce fuel consumption [3], 2) satisfying rigid future emission regulations, i.e., NOx treatment by engine control means high rates of exhaust gas recirculation (EGR) [3,4], and 3) the facilitation of high altitude opeRation [5]. However, a high Pressure Ratio causes the flow in the compressor to be transonic. Hence, the stable flow range is narrowed, since the stall incidence decreases with an increased relative Mach number at the inlet of the impeller [6]. Therefore, map width enhancement is a major issue for state-of-the-art high-Pressure-Ratio compressor design and development. A turbocharger centrifugal compressor comprises an impeller, a diffuser, and a volute. While the former two are periodically symmetric in the circumferential direction, the volute is asymmetric due to its gas-collection function. It is usually designed as a spiral-collection overhung housing that collects the air from the diffuser and passes it to the pipe system. It has been recognized that the improvement of centrifugal compressor performance requires a good understanding of the flow mechanisms inside the volute [7–9]; especially the interaction among the volute-diffuser-impeller [10,11]. The volute is mostly designed in a way to shape a uniform circumferential static Pressure distribution both in the volute and the diffuser. However, the volute acts as a diffuser at lower than the design flow rate and acts as a nozzle at higher than the design flow rate, respectively. A number of authors have researched this subject. It has already been confirmed that the asymmetrical configuRation has a significant impact on the flow field in the diffuser and in the impeller [12,13]. This circumferential asymmetry has been recognized and intensive experimental investigations of the flow within the volute and the propagation of the distortion into upstream components were carried out for subsonic compressor units [14,15]. The work of Sorokes et al. confirmed that the Pressure nonuniformity extended upstream of the impeller, implying that the impeller was subjected to varying inlet and exit conditions. The computational fluid dynamics (CFD) results further implied that the inlet flow distortion caused a large leading edge Pressure differential along with a large negative incidence, which may induce a flow sepaRation and thus a very disturbed flow field in the impeller [14]. A three-dimensional unsteady analysis of the flow in the impeller with circumferential distortion of the outlet static Pressure was investigated using a numerical method by Fatsis et al. [16]. The perturbation was thus propagated upstream from the impeller outlet and influenced the incidence at the blade leading edges and other flow parameters. Gu et al. [10,11] found that the performance parameters of the single impeller passage differed because of the asymmetric flow at the outlet of the impeller. There was almost no phase shift between the distortion in the diffuser and impeller according to their results, and it was considered that the unsteady effects of the volute-impeller interaction can be neglected when the Strouhal number is small enough. Little detailed measurement was carried out in the impeller to investigate the asymmetric flow. Furthermore, to the authors’ knowledge, very little research work has been focused on the impact of the volute on the flow field in a high-Pressure-Ratio turbocharger centrifugal compressor. The purpose of this two-part paper is first to understand the asymmetry of flow field due to the asymmetric geometry of the volute and, subsequently, to develop a novel asymmetric flow control method to widen the stable flow range of a turbocharger centrifugal compressor with a high-Pressure-Ratio, the narrowing flow range of which is of utmost importance for its application. In Part I, the nonaxisymmetrical flow characteristics in the high-Pressure-Ratio turbocharger centrifugal compressor are investigated by using experimental and numerical means, the results of which are the basis for the work presented in Part II.
-
Investigation of Self-Recycling-Casing-Treatment (SRCT) Influence on Stability of High Pressure Ratio Centrifugal Compressor With a Volute
2012Co-Authors: Mingyang Yang, Xin Qian Zheng, Ricardo F. Martinez-botas, Takeshi Bamba, Hideaki Tamaki, Yangjun Zhang, Zhigang LiAbstract:Large feasible opeRation range is a challenge for high Pressure Ratio centrifugal compressor of turbocharger in vehicle engine. Self-Recycling-Casing- Treatment (SRCT) is a widely used flow control method to enlarge the range for this kind of compressor. This paper investigates the influence of symmetrical/asymmetrical SRCT (ASRCT) on the stability of a high Pressure Ratio centrifugal compressor by experimental testing and numerical simulation. Firstly, the performance of the compressor with/without SRCT is tested is measured investigate the influence of flow distortion on the stability of compressor as well as the numerical method validation. Then detailed flow field investigation is conducted by experimental measurement and the numerical method to unveil the reasons for stability enhancement by symmetrical/asymmetrical SRCT. Results show that static Pressure distortion at impeller outlet caused by the volute can make passages be confronted with flow distortion less stable than others because of their larger positive slope of T-S Pressure Ratio performance at small flow rate. SRCT can depress the flow distortion and reduce the slope by non-uniform recycling flow rate at impeller inlet. Moreover, ASRCT can redistribute the recycling flow in circumferential direction according to the asymmetric geometries. When the largest recycling flow rate is imposed on the passage near the distorted static Pressure, the slope will be the most effectively reduced. Therefore, the stability is effectively enhanced by the optimized recycling flow device. Copyright © 2011 by ASME.
-
research and development on transonic compressor of high Pressure Ratio turbocharger for vehicle internal combustion engines
Science China-technological Sciences, 2010Co-Authors: Xin Qian Zheng, Yangjun Zhang, Mingyang YangAbstract:The Pressure Ratio required for a turbocharger centrifugal compressor increases with internal combustion engine power density. High Pressure Ratio causes a transonic flow field at the impeller inducer. Transonic flow narrows the stable flow range and deteriorates stage efficiency. In this work, an advanced high Pressure Ratio transonic compressor was designed. The experimental results show that the maximum Pressure Ratio of this turbocharger is about 4.2, the maximum efficiency is above 80% and the stable flow range at the designed rotating speed is up to 34%. A turbocharger with this transonic compressor has been applied to some vehicle research actually, and improved power density by 40%.
Yangjun Zhang - One of the best experts on this subject based on the ideXlab platform.
-
inlet duct treatment for stability improvement on a high Pressure Ratio centrifugal compressor
ASME Turbo Expo 2013: Turbine Technical Conference and Exposition, 2013Co-Authors: Mingyang Yang, Ricardo Martinezbotas, Yangjun ZhangAbstract:The operating range of a centrifugal compressor, determined by surge and choke flow rate, is a key issue for turbocharging since a vehicle internal combustion engine (ICE) is usually operated across a wide range. In this paper a new flow control method is developed and validated numerically, in which an array of circumferentially distributed holes is designed in the inner wall of the inlet duct of a high Pressure Ratio centrifugal compressor of a turbocharger. Firstly the numerical method is validated by experimental results of the original turbocharging centrifugal compressor with a Pressure Ratio of 4. Next the validated method is used to investigate the new flow control method and its effect on the compressor’s performance. Results show that the method can enhance the compressor stability and widen the operating range effectively at all investigated speeds. At meantime, the choke flow reduces slightly. The flow details in the compressor are further analysed according to the CFD results. It is found that the flow near the blade tip at inlet is pre-swirled by the method as the conventional IGV does while the flow in the middle span or near the hub remains in an axial direction. As a result, the stability of the compressor is enhanced by the pre-swirl effect at the tip while minimally sacrificing the choke flow rate, thus the map is extended effectively by the flow control method.Copyright © 2013 by ASME
-
effects of reynolds number on the performance of a high Pressure Ratio turbocharger compressor
Science China-technological Sciences, 2013Co-Authors: Xin Qian Zheng, Wei Lin Zhuge, Yangjun ZhangAbstract:The effects of Reynolds number on the performance of a high Pressure-Ratio turbocharger compressor were investigated by both experiments and numerical simulation. The experimental results show that the Pressure Ratio and the efficiency of the compressor respectively decrease by 7.9% and 6.9% when Reynolds number drops from 9.86×105 to 2.96×105. The numerical simulation predicts a similar trend as the experimental results although it underestimates the deterioRation of the performance under low Reynolds number conditions. According to simulation results, the boundary layer thickness increases at the inducer, which decreases the throat area and leads to smaller choke mass flow rate. The increments of the boundary thickness are relatively small at the rear part of the impeller. The boundary layer sepaRation flow is severe. The interaction between boundary layer sepaRation flows and leakage flows causes the high loss region at the rear part of the impeller passage under low Reynolds number condition.
-
stability improvement of high Pressure Ratio turbocharger centrifugal compressor by asymmetric flow control part i non axisymmetrical flow in centrifugal compressor
Journal of Turbomachinery-transactions of The Asme, 2013Co-Authors: Mingyang Yang, Xin Qian Zheng, Joern Huenteler, Takeshi Bamba, Hideaki Tamaki, Yangjun Zhang, Zhigang LiAbstract:The history of turbocharging is almost as old as that of the internal combustion engine. A turbocharger consists of a compressor and a turbine. The compressor is driven by the turbine extracting energy from exhaust gases. Compared to a naturally aspirated engine, the benefits of a turbocharged engine are increased power, lower fuel consumption, and reduced emissions [1,2]. High-Pressure-Ratio turbocharging technology is the developing trend of turbocharged internal combustion engines due to the following reasons: 1) significant downsizing to mitigate CO2 emission and reduce fuel consumption [3], 2) satisfying rigid future emission regulations, i.e., NOx treatment by engine control means high rates of exhaust gas recirculation (EGR) [3,4], and 3) the facilitation of high altitude opeRation [5]. However, a high Pressure Ratio causes the flow in the compressor to be transonic. Hence, the stable flow range is narrowed, since the stall incidence decreases with an increased relative Mach number at the inlet of the impeller [6]. Therefore, map width enhancement is a major issue for state-of-the-art high-Pressure-Ratio compressor design and development. A turbocharger centrifugal compressor comprises an impeller, a diffuser, and a volute. While the former two are periodically symmetric in the circumferential direction, the volute is asymmetric due to its gas-collection function. It is usually designed as a spiral-collection overhung housing that collects the air from the diffuser and passes it to the pipe system. It has been recognized that the improvement of centrifugal compressor performance requires a good understanding of the flow mechanisms inside the volute [7–9]; especially the interaction among the volute-diffuser-impeller [10,11]. The volute is mostly designed in a way to shape a uniform circumferential static Pressure distribution both in the volute and the diffuser. However, the volute acts as a diffuser at lower than the design flow rate and acts as a nozzle at higher than the design flow rate, respectively. A number of authors have researched this subject. It has already been confirmed that the asymmetrical configuRation has a significant impact on the flow field in the diffuser and in the impeller [12,13]. This circumferential asymmetry has been recognized and intensive experimental investigations of the flow within the volute and the propagation of the distortion into upstream components were carried out for subsonic compressor units [14,15]. The work of Sorokes et al. confirmed that the Pressure nonuniformity extended upstream of the impeller, implying that the impeller was subjected to varying inlet and exit conditions. The computational fluid dynamics (CFD) results further implied that the inlet flow distortion caused a large leading edge Pressure differential along with a large negative incidence, which may induce a flow sepaRation and thus a very disturbed flow field in the impeller [14]. A three-dimensional unsteady analysis of the flow in the impeller with circumferential distortion of the outlet static Pressure was investigated using a numerical method by Fatsis et al. [16]. The perturbation was thus propagated upstream from the impeller outlet and influenced the incidence at the blade leading edges and other flow parameters. Gu et al. [10,11] found that the performance parameters of the single impeller passage differed because of the asymmetric flow at the outlet of the impeller. There was almost no phase shift between the distortion in the diffuser and impeller according to their results, and it was considered that the unsteady effects of the volute-impeller interaction can be neglected when the Strouhal number is small enough. Little detailed measurement was carried out in the impeller to investigate the asymmetric flow. Furthermore, to the authors’ knowledge, very little research work has been focused on the impact of the volute on the flow field in a high-Pressure-Ratio turbocharger centrifugal compressor. The purpose of this two-part paper is first to understand the asymmetry of flow field due to the asymmetric geometry of the volute and, subsequently, to develop a novel asymmetric flow control method to widen the stable flow range of a turbocharger centrifugal compressor with a high-Pressure-Ratio, the narrowing flow range of which is of utmost importance for its application. In Part I, the nonaxisymmetrical flow characteristics in the high-Pressure-Ratio turbocharger centrifugal compressor are investigated by using experimental and numerical means, the results of which are the basis for the work presented in Part II.
-
Investigation of Self-Recycling-Casing-Treatment (SRCT) Influence on Stability of High Pressure Ratio Centrifugal Compressor With a Volute
2012Co-Authors: Mingyang Yang, Xin Qian Zheng, Ricardo F. Martinez-botas, Takeshi Bamba, Hideaki Tamaki, Yangjun Zhang, Zhigang LiAbstract:Large feasible opeRation range is a challenge for high Pressure Ratio centrifugal compressor of turbocharger in vehicle engine. Self-Recycling-Casing- Treatment (SRCT) is a widely used flow control method to enlarge the range for this kind of compressor. This paper investigates the influence of symmetrical/asymmetrical SRCT (ASRCT) on the stability of a high Pressure Ratio centrifugal compressor by experimental testing and numerical simulation. Firstly, the performance of the compressor with/without SRCT is tested is measured investigate the influence of flow distortion on the stability of compressor as well as the numerical method validation. Then detailed flow field investigation is conducted by experimental measurement and the numerical method to unveil the reasons for stability enhancement by symmetrical/asymmetrical SRCT. Results show that static Pressure distortion at impeller outlet caused by the volute can make passages be confronted with flow distortion less stable than others because of their larger positive slope of T-S Pressure Ratio performance at small flow rate. SRCT can depress the flow distortion and reduce the slope by non-uniform recycling flow rate at impeller inlet. Moreover, ASRCT can redistribute the recycling flow in circumferential direction according to the asymmetric geometries. When the largest recycling flow rate is imposed on the passage near the distorted static Pressure, the slope will be the most effectively reduced. Therefore, the stability is effectively enhanced by the optimized recycling flow device. Copyright © 2011 by ASME.
-
research and development on transonic compressor of high Pressure Ratio turbocharger for vehicle internal combustion engines
Science China-technological Sciences, 2010Co-Authors: Xin Qian Zheng, Yangjun Zhang, Mingyang YangAbstract:The Pressure Ratio required for a turbocharger centrifugal compressor increases with internal combustion engine power density. High Pressure Ratio causes a transonic flow field at the impeller inducer. Transonic flow narrows the stable flow range and deteriorates stage efficiency. In this work, an advanced high Pressure Ratio transonic compressor was designed. The experimental results show that the maximum Pressure Ratio of this turbocharger is about 4.2, the maximum efficiency is above 80% and the stable flow range at the designed rotating speed is up to 34%. A turbocharger with this transonic compressor has been applied to some vehicle research actually, and improved power density by 40%.
Takeshi Bamba - One of the best experts on this subject based on the ideXlab platform.
-
stability improvement of high Pressure Ratio turbocharger centrifugal compressor by asymmetric flow control part i non axisymmetrical flow in centrifugal compressor
Journal of Turbomachinery-transactions of The Asme, 2013Co-Authors: Mingyang Yang, Xin Qian Zheng, Joern Huenteler, Takeshi Bamba, Hideaki Tamaki, Yangjun Zhang, Zhigang LiAbstract:The history of turbocharging is almost as old as that of the internal combustion engine. A turbocharger consists of a compressor and a turbine. The compressor is driven by the turbine extracting energy from exhaust gases. Compared to a naturally aspirated engine, the benefits of a turbocharged engine are increased power, lower fuel consumption, and reduced emissions [1,2]. High-Pressure-Ratio turbocharging technology is the developing trend of turbocharged internal combustion engines due to the following reasons: 1) significant downsizing to mitigate CO2 emission and reduce fuel consumption [3], 2) satisfying rigid future emission regulations, i.e., NOx treatment by engine control means high rates of exhaust gas recirculation (EGR) [3,4], and 3) the facilitation of high altitude opeRation [5]. However, a high Pressure Ratio causes the flow in the compressor to be transonic. Hence, the stable flow range is narrowed, since the stall incidence decreases with an increased relative Mach number at the inlet of the impeller [6]. Therefore, map width enhancement is a major issue for state-of-the-art high-Pressure-Ratio compressor design and development. A turbocharger centrifugal compressor comprises an impeller, a diffuser, and a volute. While the former two are periodically symmetric in the circumferential direction, the volute is asymmetric due to its gas-collection function. It is usually designed as a spiral-collection overhung housing that collects the air from the diffuser and passes it to the pipe system. It has been recognized that the improvement of centrifugal compressor performance requires a good understanding of the flow mechanisms inside the volute [7–9]; especially the interaction among the volute-diffuser-impeller [10,11]. The volute is mostly designed in a way to shape a uniform circumferential static Pressure distribution both in the volute and the diffuser. However, the volute acts as a diffuser at lower than the design flow rate and acts as a nozzle at higher than the design flow rate, respectively. A number of authors have researched this subject. It has already been confirmed that the asymmetrical configuRation has a significant impact on the flow field in the diffuser and in the impeller [12,13]. This circumferential asymmetry has been recognized and intensive experimental investigations of the flow within the volute and the propagation of the distortion into upstream components were carried out for subsonic compressor units [14,15]. The work of Sorokes et al. confirmed that the Pressure nonuniformity extended upstream of the impeller, implying that the impeller was subjected to varying inlet and exit conditions. The computational fluid dynamics (CFD) results further implied that the inlet flow distortion caused a large leading edge Pressure differential along with a large negative incidence, which may induce a flow sepaRation and thus a very disturbed flow field in the impeller [14]. A three-dimensional unsteady analysis of the flow in the impeller with circumferential distortion of the outlet static Pressure was investigated using a numerical method by Fatsis et al. [16]. The perturbation was thus propagated upstream from the impeller outlet and influenced the incidence at the blade leading edges and other flow parameters. Gu et al. [10,11] found that the performance parameters of the single impeller passage differed because of the asymmetric flow at the outlet of the impeller. There was almost no phase shift between the distortion in the diffuser and impeller according to their results, and it was considered that the unsteady effects of the volute-impeller interaction can be neglected when the Strouhal number is small enough. Little detailed measurement was carried out in the impeller to investigate the asymmetric flow. Furthermore, to the authors’ knowledge, very little research work has been focused on the impact of the volute on the flow field in a high-Pressure-Ratio turbocharger centrifugal compressor. The purpose of this two-part paper is first to understand the asymmetry of flow field due to the asymmetric geometry of the volute and, subsequently, to develop a novel asymmetric flow control method to widen the stable flow range of a turbocharger centrifugal compressor with a high-Pressure-Ratio, the narrowing flow range of which is of utmost importance for its application. In Part I, the nonaxisymmetrical flow characteristics in the high-Pressure-Ratio turbocharger centrifugal compressor are investigated by using experimental and numerical means, the results of which are the basis for the work presented in Part II.
-
Investigation of Self-Recycling-Casing-Treatment (SRCT) Influence on Stability of High Pressure Ratio Centrifugal Compressor With a Volute
2012Co-Authors: Mingyang Yang, Xin Qian Zheng, Ricardo F. Martinez-botas, Takeshi Bamba, Hideaki Tamaki, Yangjun Zhang, Zhigang LiAbstract:Large feasible opeRation range is a challenge for high Pressure Ratio centrifugal compressor of turbocharger in vehicle engine. Self-Recycling-Casing- Treatment (SRCT) is a widely used flow control method to enlarge the range for this kind of compressor. This paper investigates the influence of symmetrical/asymmetrical SRCT (ASRCT) on the stability of a high Pressure Ratio centrifugal compressor by experimental testing and numerical simulation. Firstly, the performance of the compressor with/without SRCT is tested is measured investigate the influence of flow distortion on the stability of compressor as well as the numerical method validation. Then detailed flow field investigation is conducted by experimental measurement and the numerical method to unveil the reasons for stability enhancement by symmetrical/asymmetrical SRCT. Results show that static Pressure distortion at impeller outlet caused by the volute can make passages be confronted with flow distortion less stable than others because of their larger positive slope of T-S Pressure Ratio performance at small flow rate. SRCT can depress the flow distortion and reduce the slope by non-uniform recycling flow rate at impeller inlet. Moreover, ASRCT can redistribute the recycling flow in circumferential direction according to the asymmetric geometries. When the largest recycling flow rate is imposed on the passage near the distorted static Pressure, the slope will be the most effectively reduced. Therefore, the stability is effectively enhanced by the optimized recycling flow device. Copyright © 2011 by ASME.
-
Influence of the volute on the flow in a centrifugal compressor of a high-Pressure Ratio turbocharger
Proceedings of the Institution of Mechanical Engineers Part A: Journal of Power and Energy, 2010Co-Authors: Joern Huenteler, Y J Zhang, Takeshi Bamba, M. Y. YangAbstract:The asymmetric influence of the volute on the flow in a transonic, high-Pressure Ratio centrifugal compressor at off-design conditions was investigated. Fully three-dimensional viscous steady-state computational fluid dynamics (CFD) was applied to simulate the flow in a 4.2:1 design Pressure Ratio compressor for automotive application. Computed performance characteristic are presented for low- and high-Pressure operating conditions, with and without an overhung volute. The volute was found to severely harm aerodynamic stability of the investigated compressor when operating at lower than design mass flow. The relative narrowing effect of the volute on compressor map width increases with Pressure Ratio up to a 42 per cent drop in stable flow range at design speed. The inter-passage variations in performance quantities and the influence of the volute tongue region are discused in detail. The circumferential variations of incidence angle correlate with rotational speed, which, in combination with the higher sensitivity to incidence angle at transonic inflow conditions, seems to deteriorates stability when transonic inflow conditions are reached.
Zhigang Li - One of the best experts on this subject based on the ideXlab platform.
-
stability improvement of high Pressure Ratio turbocharger centrifugal compressor by asymmetric flow control part i non axisymmetrical flow in centrifugal compressor
Journal of Turbomachinery-transactions of The Asme, 2013Co-Authors: Mingyang Yang, Xin Qian Zheng, Joern Huenteler, Takeshi Bamba, Hideaki Tamaki, Yangjun Zhang, Zhigang LiAbstract:The history of turbocharging is almost as old as that of the internal combustion engine. A turbocharger consists of a compressor and a turbine. The compressor is driven by the turbine extracting energy from exhaust gases. Compared to a naturally aspirated engine, the benefits of a turbocharged engine are increased power, lower fuel consumption, and reduced emissions [1,2]. High-Pressure-Ratio turbocharging technology is the developing trend of turbocharged internal combustion engines due to the following reasons: 1) significant downsizing to mitigate CO2 emission and reduce fuel consumption [3], 2) satisfying rigid future emission regulations, i.e., NOx treatment by engine control means high rates of exhaust gas recirculation (EGR) [3,4], and 3) the facilitation of high altitude opeRation [5]. However, a high Pressure Ratio causes the flow in the compressor to be transonic. Hence, the stable flow range is narrowed, since the stall incidence decreases with an increased relative Mach number at the inlet of the impeller [6]. Therefore, map width enhancement is a major issue for state-of-the-art high-Pressure-Ratio compressor design and development. A turbocharger centrifugal compressor comprises an impeller, a diffuser, and a volute. While the former two are periodically symmetric in the circumferential direction, the volute is asymmetric due to its gas-collection function. It is usually designed as a spiral-collection overhung housing that collects the air from the diffuser and passes it to the pipe system. It has been recognized that the improvement of centrifugal compressor performance requires a good understanding of the flow mechanisms inside the volute [7–9]; especially the interaction among the volute-diffuser-impeller [10,11]. The volute is mostly designed in a way to shape a uniform circumferential static Pressure distribution both in the volute and the diffuser. However, the volute acts as a diffuser at lower than the design flow rate and acts as a nozzle at higher than the design flow rate, respectively. A number of authors have researched this subject. It has already been confirmed that the asymmetrical configuRation has a significant impact on the flow field in the diffuser and in the impeller [12,13]. This circumferential asymmetry has been recognized and intensive experimental investigations of the flow within the volute and the propagation of the distortion into upstream components were carried out for subsonic compressor units [14,15]. The work of Sorokes et al. confirmed that the Pressure nonuniformity extended upstream of the impeller, implying that the impeller was subjected to varying inlet and exit conditions. The computational fluid dynamics (CFD) results further implied that the inlet flow distortion caused a large leading edge Pressure differential along with a large negative incidence, which may induce a flow sepaRation and thus a very disturbed flow field in the impeller [14]. A three-dimensional unsteady analysis of the flow in the impeller with circumferential distortion of the outlet static Pressure was investigated using a numerical method by Fatsis et al. [16]. The perturbation was thus propagated upstream from the impeller outlet and influenced the incidence at the blade leading edges and other flow parameters. Gu et al. [10,11] found that the performance parameters of the single impeller passage differed because of the asymmetric flow at the outlet of the impeller. There was almost no phase shift between the distortion in the diffuser and impeller according to their results, and it was considered that the unsteady effects of the volute-impeller interaction can be neglected when the Strouhal number is small enough. Little detailed measurement was carried out in the impeller to investigate the asymmetric flow. Furthermore, to the authors’ knowledge, very little research work has been focused on the impact of the volute on the flow field in a high-Pressure-Ratio turbocharger centrifugal compressor. The purpose of this two-part paper is first to understand the asymmetry of flow field due to the asymmetric geometry of the volute and, subsequently, to develop a novel asymmetric flow control method to widen the stable flow range of a turbocharger centrifugal compressor with a high-Pressure-Ratio, the narrowing flow range of which is of utmost importance for its application. In Part I, the nonaxisymmetrical flow characteristics in the high-Pressure-Ratio turbocharger centrifugal compressor are investigated by using experimental and numerical means, the results of which are the basis for the work presented in Part II.
-
Investigation of Self-Recycling-Casing-Treatment (SRCT) Influence on Stability of High Pressure Ratio Centrifugal Compressor With a Volute
2012Co-Authors: Mingyang Yang, Xin Qian Zheng, Ricardo F. Martinez-botas, Takeshi Bamba, Hideaki Tamaki, Yangjun Zhang, Zhigang LiAbstract:Large feasible opeRation range is a challenge for high Pressure Ratio centrifugal compressor of turbocharger in vehicle engine. Self-Recycling-Casing- Treatment (SRCT) is a widely used flow control method to enlarge the range for this kind of compressor. This paper investigates the influence of symmetrical/asymmetrical SRCT (ASRCT) on the stability of a high Pressure Ratio centrifugal compressor by experimental testing and numerical simulation. Firstly, the performance of the compressor with/without SRCT is tested is measured investigate the influence of flow distortion on the stability of compressor as well as the numerical method validation. Then detailed flow field investigation is conducted by experimental measurement and the numerical method to unveil the reasons for stability enhancement by symmetrical/asymmetrical SRCT. Results show that static Pressure distortion at impeller outlet caused by the volute can make passages be confronted with flow distortion less stable than others because of their larger positive slope of T-S Pressure Ratio performance at small flow rate. SRCT can depress the flow distortion and reduce the slope by non-uniform recycling flow rate at impeller inlet. Moreover, ASRCT can redistribute the recycling flow in circumferential direction according to the asymmetric geometries. When the largest recycling flow rate is imposed on the passage near the distorted static Pressure, the slope will be the most effectively reduced. Therefore, the stability is effectively enhanced by the optimized recycling flow device. Copyright © 2011 by ASME.
-
effects of Pressure Ratio and rotational speed on leakage flow and cavity Pressure in the staggered labyrinth seal
Journal of Engineering for Gas Turbines and Power-transactions of The Asme, 2011Co-Authors: Zhigang Li, Jun Li, Zhenping FengAbstract:Effects of Pressure Ratio and rotational speed on the leakage flow and cavity Pressure characteristics of the rotating staggered labyrinth seal were investigated by means of experimental measurements and numerical simulations. The rotating seal test rig with turbine flowmeter and Pressure measuring instruments was utilized to investigate the leakage flow of the staggered labyrinth seal at eight Pressure Ratios and five rotational speeds. The repeatability of the experimental data was demonstrated by three times measurements at different Pressure Ratios and fixed rotational speed. The three-dimensional Reynolds-averaged Navier–Stokes equations and standard k-e turbulent model were also applied to study the leakage flow characteristics of the staggered labyrinth seal at the experimental conditions. The validation of the numerical approach was verified through comparison of the experimental data. The detailed flow field in the staggered labyrinth seal was illustrated according to the numerical simulations. The experimental and numerical results show that the leakage flow coefficient increases with increasing Pressure Ratio at the fixed rotational speed and is more sensitive to the smaller Pressure Ratio. The influence of rotational speed on the leakage flow coefficient is not obvious in the present rotational speed limitations. The cavity Pressure coefficient in the staggered labyrinth seal decreases and is significantly influenced by the cavity structure along the flow direction.
