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Changmao Yang - One of the best experts on this subject based on the ideXlab platform.
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Investigation on the Stall Inception Circumferential Position and Stall Process Behavior in a Centrifugal Compressor With Volute
Journal of Engineering for Gas Turbines and Power, 2018Co-Authors: Hanzhi Zhang, Ce Yang, Dengfeng Yang, Wenli Wang, Changmao YangAbstract:The present paper numerically and experimentally investigates the stall inception mechanisms in a centrifugal compressor with volute. Current studies about stall inception pay more attention on the axial compressors than the centrifugal compressors; especially, the circumferential position of stall inception onset and the stall process in the centrifugal compressor with asymmetric volute structure have not been studied sufficiently yet. In this work, the compressor performance experiment was conducted and the casing wall Static Pressure distributions were obtained by 72 Static Pressure sensors first. Then, the full annular unsteady simulations were carried out at different stable operating points, and the time-averaged Static Pressure distributions were compared with the experimental results. Finally, the stall process of the compressor was investigated by unsteady simulations in detail. Results show that the stall inception onset is determined by the impeller leading edge (LE) spillage flow, and the occurrence time of trailing edge (TE) backflow is prior to the LE spillage. The nonuniform Static Pressure circumferential distribution at impeller Outlet induced by volute tongue causes the two stall inception regions locating at certain circumferential positions, which are 120 deg and 300 deg circumferential positions at impeller LE, corresponding to the circumferential Static Pressure peak (PP) and bulge regions at impeller Outlet, respectively. In detail, at rotor revolution 2.86, a small disturbance that the incoming/tip clearance flow interface is perpendicular to axial direction occurs at 120 deg position, but this disturbance did not cause the compressor stall. Then at revolution 7, the first stall inception zone (spillage region) occurs at 120 deg position, causing the compressor stall with positive Pressure ratio performance. At approximately revolution 23, the second stall inception zone occurs at about 300 deg position; however, both the intensity and size of this stall inception zone are smaller than those of the first stall inception zone. These two stall inception zones are not moving along circumferential direction because the stall inception circumferential position is dominated by the impeller Outlet Static Pressure distribution. Even then, the obvious low frequency signals appear after the spillage crossing two blade LEs, because at this moment, the spillage vortex caused by the tip leakage flow begins to shed. However, due to the asymmetric structure limitation, this vortex cannot move across full annular. Furthermore, the spillage vortexes cause the local low Static Pressure zone ahead of blade LE in the centrifugal compressor with volute, suggesting that the spillage can be predicted by the steady casing wall Static Pressure measuring. The development of blockage zones at impeller LE is also investigated quantitatively by analyzing the stall blockage effect.
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Investigation on the Stall Inception Circumferential Position and Stall Process Behavior in a Centrifugal Compressor With Volute
Volume 2B: Turbomachinery, 2018Co-Authors: Hanzhi Zhang, Ce Yang, Dengfeng Yang, Wenli Wang, Changmao YangAbstract:The present paper numerically and experimentally investigates the stall inception mechanisms in a centrifugal compressor with volute. Current studies about stall inception pay more attention on the axial compressors than the centrifugal compressors; especially, the circumferential position of stall inception onset and the stall process in the centrifugal compressor with asymmetric volute structure have not been studied sufficiently yet. In this work, the compressor performance experiment was conducted and the casing wall Static Pressure distributions were obtained by seventy-two Static Pressure sensors firstly. Then, the full annular unsteady simulations were carried out at different stable operating points, and the time-averaged Static Pressure distributions were compared with the experimental results. Finally, the stall process of the compressor was investigated by unsteady simulations in detail. Results show that the stall inception onset is determined by the impeller leading edge spillage flow, and the occurrence time of trailing edge backflow is prior to the leading edge spillage. The non-uniform Static Pressure circumferential distribution at impeller Outlet induced by volute tongue causes the two stall inception regions locating at certain circumferential positions, which are 120° and 300° circumferential positions at impeller leading edge, corresponding to the circumferential Static Pressure peak and bulge regions at impeller Outlet, respectively. In detail, at rotor revolution 2.86, a small disturbance that the incoming/tip clearance flow interface is perpendicular to axial direction occurs at 120° position, but this disturbance did not cause the compressor stall. Then at revolution 7, the first stall inception zone (spillage region) occurs at 120° position, causing the compressor stall with positive Pressure ratio performance. At approximately revolution 23, the second stall inception zone occurs at about 300° position; however, both the intensity and size of this stall inception zone are smaller than those of the first stall inception zone. These two stall inception zones are not moving along circumferential direction because the stall inception circumferential position is dominated by the impeller Outlet Static Pressure distribution. Even that, the obvious low frequency signals appear after the spillage crossing two blade leading edges; because at this moment, the spillage vortex caused by the tip leakage flow begins to shed. However, due to the asymmetric structure limitation, this vortex cannot move across full annular. Furthermore, the spillage vortexes cause the local low Static Pressure zone ahead of blade leading edge in the centrifugal compressor with volute, suggesting that the spillage can be predicted by the steady casing wall Static Pressure measuring. The development of blockage zones at impeller leading edge is also investigated quantitatively by analyzing the stall blockage effect.
Hanzhi Zhang - One of the best experts on this subject based on the ideXlab platform.
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Investigation on the Stall Inception Circumferential Position and Stall Process Behavior in a Centrifugal Compressor With Volute
Journal of Engineering for Gas Turbines and Power, 2018Co-Authors: Hanzhi Zhang, Ce Yang, Dengfeng Yang, Wenli Wang, Changmao YangAbstract:The present paper numerically and experimentally investigates the stall inception mechanisms in a centrifugal compressor with volute. Current studies about stall inception pay more attention on the axial compressors than the centrifugal compressors; especially, the circumferential position of stall inception onset and the stall process in the centrifugal compressor with asymmetric volute structure have not been studied sufficiently yet. In this work, the compressor performance experiment was conducted and the casing wall Static Pressure distributions were obtained by 72 Static Pressure sensors first. Then, the full annular unsteady simulations were carried out at different stable operating points, and the time-averaged Static Pressure distributions were compared with the experimental results. Finally, the stall process of the compressor was investigated by unsteady simulations in detail. Results show that the stall inception onset is determined by the impeller leading edge (LE) spillage flow, and the occurrence time of trailing edge (TE) backflow is prior to the LE spillage. The nonuniform Static Pressure circumferential distribution at impeller Outlet induced by volute tongue causes the two stall inception regions locating at certain circumferential positions, which are 120 deg and 300 deg circumferential positions at impeller LE, corresponding to the circumferential Static Pressure peak (PP) and bulge regions at impeller Outlet, respectively. In detail, at rotor revolution 2.86, a small disturbance that the incoming/tip clearance flow interface is perpendicular to axial direction occurs at 120 deg position, but this disturbance did not cause the compressor stall. Then at revolution 7, the first stall inception zone (spillage region) occurs at 120 deg position, causing the compressor stall with positive Pressure ratio performance. At approximately revolution 23, the second stall inception zone occurs at about 300 deg position; however, both the intensity and size of this stall inception zone are smaller than those of the first stall inception zone. These two stall inception zones are not moving along circumferential direction because the stall inception circumferential position is dominated by the impeller Outlet Static Pressure distribution. Even then, the obvious low frequency signals appear after the spillage crossing two blade LEs, because at this moment, the spillage vortex caused by the tip leakage flow begins to shed. However, due to the asymmetric structure limitation, this vortex cannot move across full annular. Furthermore, the spillage vortexes cause the local low Static Pressure zone ahead of blade LE in the centrifugal compressor with volute, suggesting that the spillage can be predicted by the steady casing wall Static Pressure measuring. The development of blockage zones at impeller LE is also investigated quantitatively by analyzing the stall blockage effect.
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Investigation on the Stall Inception Circumferential Position and Stall Process Behavior in a Centrifugal Compressor With Volute
Volume 2B: Turbomachinery, 2018Co-Authors: Hanzhi Zhang, Ce Yang, Dengfeng Yang, Wenli Wang, Changmao YangAbstract:The present paper numerically and experimentally investigates the stall inception mechanisms in a centrifugal compressor with volute. Current studies about stall inception pay more attention on the axial compressors than the centrifugal compressors; especially, the circumferential position of stall inception onset and the stall process in the centrifugal compressor with asymmetric volute structure have not been studied sufficiently yet. In this work, the compressor performance experiment was conducted and the casing wall Static Pressure distributions were obtained by seventy-two Static Pressure sensors firstly. Then, the full annular unsteady simulations were carried out at different stable operating points, and the time-averaged Static Pressure distributions were compared with the experimental results. Finally, the stall process of the compressor was investigated by unsteady simulations in detail. Results show that the stall inception onset is determined by the impeller leading edge spillage flow, and the occurrence time of trailing edge backflow is prior to the leading edge spillage. The non-uniform Static Pressure circumferential distribution at impeller Outlet induced by volute tongue causes the two stall inception regions locating at certain circumferential positions, which are 120° and 300° circumferential positions at impeller leading edge, corresponding to the circumferential Static Pressure peak and bulge regions at impeller Outlet, respectively. In detail, at rotor revolution 2.86, a small disturbance that the incoming/tip clearance flow interface is perpendicular to axial direction occurs at 120° position, but this disturbance did not cause the compressor stall. Then at revolution 7, the first stall inception zone (spillage region) occurs at 120° position, causing the compressor stall with positive Pressure ratio performance. At approximately revolution 23, the second stall inception zone occurs at about 300° position; however, both the intensity and size of this stall inception zone are smaller than those of the first stall inception zone. These two stall inception zones are not moving along circumferential direction because the stall inception circumferential position is dominated by the impeller Outlet Static Pressure distribution. Even that, the obvious low frequency signals appear after the spillage crossing two blade leading edges; because at this moment, the spillage vortex caused by the tip leakage flow begins to shed. However, due to the asymmetric structure limitation, this vortex cannot move across full annular. Furthermore, the spillage vortexes cause the local low Static Pressure zone ahead of blade leading edge in the centrifugal compressor with volute, suggesting that the spillage can be predicted by the steady casing wall Static Pressure measuring. The development of blockage zones at impeller leading edge is also investigated quantitatively by analyzing the stall blockage effect.
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Investigation of the Coupling Mechanism Between Bent Pipes and Volute on the Stall Inception at the Centrifugal Compressor Inlet
Volume 2C: Turbomachinery, 2017Co-Authors: Ce Yang, Yingjun Wang, Dazhong Lao, Hanzhi Zhang, Ding TongAbstract:The rotating stall of a centrifugal compressor not only deteriorates its efficiency but also impacts the blade fatigue failure. The inlet total Pressure distortion is generated by a 90° bent pipe placed upstream from the inlet. The volute causes the circumferential non-uniform Static Pressure distribution of the impeller Outlet, and the impeller is under the inlet distortion and the non-uniform Outlet distribution condition. Current research pays little attention to the stall inception location and its formation process under the coupling interaction between the bent pipe and volute. In this paper, two installation angles of the inlet bent pipe were compared concerning the stall inception process, including the 115° (M1) and the 295° (M2) models. The circumferential angle between the volute tongue and the elbow axial plane approaches a blade passage width in model M1, and model M2 has the opposite installation angle to M1. The model M1 inlet low total Pressure region caused by the bent pipe, and the Outlet high Static Pressure region induced by the volute tongue together affect the same impeller passage at the 115° location causing the leading edge spillover. The coupling effect of the Model M1 accelerates the process of stall. However, the low total Pressure region for the model M2 is located at the circumferential 295° point, and the high Static Outlet Pressure affects the 115° impellers, resulting in a different stall inception location and process compared to the model M1. The leading edge spillover first occurs at the 295° location because of inlet distortion, and the second spillover appears at the 115° location due to the reversed propagation of the Outlet high Pressure region induced by the volute tongue. Compared to model M1, the stall formation of model M2 is relatively slow. Meanwhile, because of the recirculation flow, the Static temperature rises sharply and the axial velocity drops significantly at the spillover region during the stall process. These results indicate that the coupling interaction between the low total inlet Pressure and the high Outlet Static Pressure jointly determines the stall inception location and its process at the centrifugal compressor inlet.
Massimo Capobianco - One of the best experts on this subject based on the ideXlab platform.
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pulsating flow performance of a turbocharger compressor for automotive application
International Journal of Heat and Fluid Flow, 2014Co-Authors: Silvia Marelli, Massimo Capobianco, Giorgio ZamboniAbstract:Abstract Downsizing with turbocharging is the most promising way, especially in terms of cost, to get reduced fuel consumption and CO 2 emissions particularly in the case of Spark Ignition engines. In automotive applications the turbocharger turbine usually operates under heavy unsteady flow conditions due to the opening and closing of engine valves. However, in the case of extremely downsized engines with a reduced number of cylinders and a small intake circuit volume also the compressor performance can be affected by the unsteady flow generated by the engine intake valves. To make simulation models able to accurately predict engine performance, a better understanding of compressor and turbine pulsating flow performance can be accomplished through measurements performed on specialized test facilities, using suitable measuring equipment. As regards the turbocharger compressor, the surge line position under pulsating flow conditions is another important aspect to be considered. In the paper the results of a broad experimental investigation performed on a small turbocharger compressor matched to a downsized gasoline engine are presented. Measurements were developed on the test facility operating at the University of Genoa, which allows investigations on automotive turbochargers both under steady and unsteady flow conditions. Tested turbocharger compressor was coupled to the automotive engine intake circuit and the pulsating flow was generated by a motor-driven cylinder head fitted with a variable valve actuation system. Different levels of turbocharger rotational speed and different intake valve opening strategies were considered. For each operating condition compressor unsteady performance was evaluated starting from measurement of several instantaneous parameters (inlet and Outlet Static Pressure, mass flow rate and turbocharger rotational speed). A significant deviation of compressor instantaneous performance from steady state was observed, resulting in a hysteresis loop surrounding the steady state curve.
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1D Simulation and Experimental Analysis of a Turbocharger Turbine for Automotive Engines Under Steady and Unsteady Flow Conditions
Energy Procedia, 2014Co-Authors: Vincenzo De Bellis, Silvia Marelli, Fabio Bozza, Massimo CapobiancoAbstract:Abstract Turbocharging technique is more and more widely employed on compression ignition and spark ignition internal combustion engines, as well, to improve performance and reduce total displacement. Experimental studies, developed on dedicated test facilities, can supply a lot of information to optimize the engine-turbocharger matching, especially if tests can be extended to the typical engine operating conditions (unsteady flow). A specialized components test rig (particularly suited to study automotive turbochargers) has been operating since several years at the University of Genoa. The test facility allows to develop studies under steady or unsteady flow conditions both on single components and subassemblies of engine intake and exhaust circuit. In the paper the results of an experimental campaign developed on a turbocharger waste-gated turbine for gasoline engine application are presented. Preliminarily, the measurement of the turbine steady flow performance map is carried out. In a second step the same component is tested under unsteady flow conditions. Instantaneous inlet and Outlet Static Pressure, mass flow rate and turbocharger rotational speed are measured, together with average inlet and Outlet temperatures. A numerical procedure, recently developed at the University of Naples, is then utilized to predict the steady turbine performance map, following a 1D approach. The model geometrically schematizes the component basing on few linear and angular dimensions directly measured on the hardware. Then, the 1D steady flow equations are solved within the stationary and rotating channels constituting the device. All the main flow losses are properly taken into account in the model. The procedure is able to provide the sole “wheel-map” and the overall turbine map. After a tuning, the overall turbine map is compared with the experimental one, showing a very good agreement. Moreover, in order to improve the accuracy of a 1D engine simulation model, the classical map-based approach is suitably corrected with a sequence of pipes that schematizes each component of the device (inlet/Outlet ducts, volute and wheel) included upstream and downstream the turbine to account for the wave propagation and accumulation phenomena inside the machine. In this case, the previously computed “wheel-map” is utilized. The turbine pipes dimensions, are automatically provided by the geometrical module of the proposed procedure to correctly reproduce the device volume and the flow path length.
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Experimental investigation under unsteady flow conditions on turbocharger compressors for automotive gasoline engines
10th International Conference on Turbochargers and Turbocharging, 2012Co-Authors: Silvia Marelli, Massimo CapobiancoAbstract:ABSTRACT Downsizing with turbocharging is today considered an effective way to get reduced CO2 emissions of automotive gasoline engines. An important aspect to take into account is the turbocharger behaviour under the strong unsteady flow conditions occurring in downsized engines intake and exhaust circuit. A better understanding of compressor and turbine pulsating flow performance can be accomplished through dedicated experimental investigations. This information can be a fundamental requisite to make simulation models able to accurately predict engine performance. Besides, the change of the compressor surge limit under pulsating flow conditions is another important phenomenon to be considered. In the paper the results of a broad experimental investigation performed on different turbocharger compressors matched to downsized gasoline engines are presented. Measurements were developed on the test facility operating at the University of Genoa, which allows investigations on automotive turbochargers both under steady and unsteady flow conditions. Tested turbocharger compressors were coupled to the current production engine intake circuit and the pulsating flow was generated by two different motor-driven cylinder heads fitted with a variable valve actuation system. Different levels of turbocharger rotational speed and pulse frequency were considered, also taking into account different intake valve opening strategies. For each operating condition compressor unsteady performance was evaluated starting from measurement of several instantaneous parameters (inlet and Outlet Static Pressure, mass flow rate and turbocharger rotational speed). In the paper the influence of flow unsteadiness on compressor performance is analysed, referring to both 4-cylinder and 2-cylinder engine configuration.
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experimental analysis of unsteady flow performance in an automotive turbocharger turbine fitted with a waste gate valve
Proceedings of the Institution of Mechanical Engineers Part D: Journal of Automobile Engineering, 2011Co-Authors: Massimo Capobianco, Silvia MarelliAbstract:Downsizing and turbocharging is today an effective way of enhancing fuel economy in automotive engines. However, more information on compressor and turbine behaviour when working under unsteady flow conditions typically occurring in automotive turbocharged engines is still required to improve simulation models.The results of an experimental investigation into a small turbocharger turbine fitted with a waste-gate valve are presented in this paper. Turbine performance was measured under both steady and unsteady flow operation. Particular attention was given to pulsating flow performance, evaluated starting from the measurement of instantaneous parameters (inlet and Outlet Static Pressure, mass flowrate, and turbocharger rotational speed). The effect of flow unsteadiness on turbine behaviour is analysed, referring to different pulse frequencies and waste-gate settings.The paper highlights that steady and unsteady turbine performance when the waste-gate valve is partially or totally open should be known in or...
Herman Deconinck - One of the best experts on this subject based on the ideXlab platform.
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A Novel Two-Dimensional Viscous Inverse Design Method for Turbomachinery Blading
Journal of Turbomachinery, 2003Co-Authors: L. De Vito, R. A. Van Den Braembussche, Herman DeconinckAbstract:This paper presents a novel iterative viscous inverse design method for turbomachinery blading. It is made up of two steps: the first one consists of an analysis by means of a Navier-Stokes solver; the second one is an inverse design by means of an Euler solver The inverse design resorts to the concept of permeable wall, and recycles the ingredients of Demeulenaere's inviscid inverse design method that was proven fast and robust. The re-design of the LS89 turbine nozzle blade, starting from different arbitrary profiles at subsonic and transonic flow regimes, demonstrates the merits of this approach. The method may result in more than one blade profile that meets the objective, i.e., that produces the viscous target Pressure distribution. To select one particular solution among all candidates, a target mass flow is enforced by adjusting the Outlet Static Pressure. The resulting profiles are smooth (oscillation-free). The design of turbine blades with arbitrary Pressure distribution at transonic and supersonic outflow illustrates the correct behavior of the method for a large range of applications. The approach is flexible because only the pitch chord ratio is fixed and no limitations are imposed on the stagger angle.
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A Novel Two Dimensional Viscous Inverse Design Method for Turbomachinery Blading
Volume 5: Turbo Expo 2002 Parts A and B, 2002Co-Authors: L. De Vito, R. A. Van Den Braembussche, Herman DeconinckAbstract:This paper presents a novel iterative viscous inverse method for turbomachinery blading design. It is made up of two steps: The first one consists of an analysis by means of a Navier-Stokes solver, the second one is an inverse design by means of an Euler solver. The inverse design resorts to the concept of permeable wall, and recycles the ingredients of Demeulenaere’s inviscid inverse design method that was proven fast and robust. The re-design of the LS89 turbine nozzle blade, starting from different arbitrary profiles at subsonic and transonic flow regimes, demonstrates the merits of this approach. The method may result in more than one blade profile that meets the objective, i.e. that produces the viscous target Pressure distribution. To select one particular solution among all candidates, a target mass flow is enforced by adjusting the Outlet Static Pressure. The resulting profiles are smooth (oscillation-free). The design of turbine blades with arbitrary Pressure distribution at transonic and supersonic outflow illustrates the correct behavior of the method for a large range of applications. The approach is flexible because only the pitch chord ratio is fixed and no limitations are imposed on the stagger angle.Copyright © 2002 by ASME
Ce Yang - One of the best experts on this subject based on the ideXlab platform.
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Investigation on the Stall Inception Circumferential Position and Stall Process Behavior in a Centrifugal Compressor With Volute
Journal of Engineering for Gas Turbines and Power, 2018Co-Authors: Hanzhi Zhang, Ce Yang, Dengfeng Yang, Wenli Wang, Changmao YangAbstract:The present paper numerically and experimentally investigates the stall inception mechanisms in a centrifugal compressor with volute. Current studies about stall inception pay more attention on the axial compressors than the centrifugal compressors; especially, the circumferential position of stall inception onset and the stall process in the centrifugal compressor with asymmetric volute structure have not been studied sufficiently yet. In this work, the compressor performance experiment was conducted and the casing wall Static Pressure distributions were obtained by 72 Static Pressure sensors first. Then, the full annular unsteady simulations were carried out at different stable operating points, and the time-averaged Static Pressure distributions were compared with the experimental results. Finally, the stall process of the compressor was investigated by unsteady simulations in detail. Results show that the stall inception onset is determined by the impeller leading edge (LE) spillage flow, and the occurrence time of trailing edge (TE) backflow is prior to the LE spillage. The nonuniform Static Pressure circumferential distribution at impeller Outlet induced by volute tongue causes the two stall inception regions locating at certain circumferential positions, which are 120 deg and 300 deg circumferential positions at impeller LE, corresponding to the circumferential Static Pressure peak (PP) and bulge regions at impeller Outlet, respectively. In detail, at rotor revolution 2.86, a small disturbance that the incoming/tip clearance flow interface is perpendicular to axial direction occurs at 120 deg position, but this disturbance did not cause the compressor stall. Then at revolution 7, the first stall inception zone (spillage region) occurs at 120 deg position, causing the compressor stall with positive Pressure ratio performance. At approximately revolution 23, the second stall inception zone occurs at about 300 deg position; however, both the intensity and size of this stall inception zone are smaller than those of the first stall inception zone. These two stall inception zones are not moving along circumferential direction because the stall inception circumferential position is dominated by the impeller Outlet Static Pressure distribution. Even then, the obvious low frequency signals appear after the spillage crossing two blade LEs, because at this moment, the spillage vortex caused by the tip leakage flow begins to shed. However, due to the asymmetric structure limitation, this vortex cannot move across full annular. Furthermore, the spillage vortexes cause the local low Static Pressure zone ahead of blade LE in the centrifugal compressor with volute, suggesting that the spillage can be predicted by the steady casing wall Static Pressure measuring. The development of blockage zones at impeller LE is also investigated quantitatively by analyzing the stall blockage effect.
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Investigation on the Stall Inception Circumferential Position and Stall Process Behavior in a Centrifugal Compressor With Volute
Volume 2B: Turbomachinery, 2018Co-Authors: Hanzhi Zhang, Ce Yang, Dengfeng Yang, Wenli Wang, Changmao YangAbstract:The present paper numerically and experimentally investigates the stall inception mechanisms in a centrifugal compressor with volute. Current studies about stall inception pay more attention on the axial compressors than the centrifugal compressors; especially, the circumferential position of stall inception onset and the stall process in the centrifugal compressor with asymmetric volute structure have not been studied sufficiently yet. In this work, the compressor performance experiment was conducted and the casing wall Static Pressure distributions were obtained by seventy-two Static Pressure sensors firstly. Then, the full annular unsteady simulations were carried out at different stable operating points, and the time-averaged Static Pressure distributions were compared with the experimental results. Finally, the stall process of the compressor was investigated by unsteady simulations in detail. Results show that the stall inception onset is determined by the impeller leading edge spillage flow, and the occurrence time of trailing edge backflow is prior to the leading edge spillage. The non-uniform Static Pressure circumferential distribution at impeller Outlet induced by volute tongue causes the two stall inception regions locating at certain circumferential positions, which are 120° and 300° circumferential positions at impeller leading edge, corresponding to the circumferential Static Pressure peak and bulge regions at impeller Outlet, respectively. In detail, at rotor revolution 2.86, a small disturbance that the incoming/tip clearance flow interface is perpendicular to axial direction occurs at 120° position, but this disturbance did not cause the compressor stall. Then at revolution 7, the first stall inception zone (spillage region) occurs at 120° position, causing the compressor stall with positive Pressure ratio performance. At approximately revolution 23, the second stall inception zone occurs at about 300° position; however, both the intensity and size of this stall inception zone are smaller than those of the first stall inception zone. These two stall inception zones are not moving along circumferential direction because the stall inception circumferential position is dominated by the impeller Outlet Static Pressure distribution. Even that, the obvious low frequency signals appear after the spillage crossing two blade leading edges; because at this moment, the spillage vortex caused by the tip leakage flow begins to shed. However, due to the asymmetric structure limitation, this vortex cannot move across full annular. Furthermore, the spillage vortexes cause the local low Static Pressure zone ahead of blade leading edge in the centrifugal compressor with volute, suggesting that the spillage can be predicted by the steady casing wall Static Pressure measuring. The development of blockage zones at impeller leading edge is also investigated quantitatively by analyzing the stall blockage effect.
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Investigation of the Coupling Mechanism Between Bent Pipes and Volute on the Stall Inception at the Centrifugal Compressor Inlet
Volume 2C: Turbomachinery, 2017Co-Authors: Ce Yang, Yingjun Wang, Dazhong Lao, Hanzhi Zhang, Ding TongAbstract:The rotating stall of a centrifugal compressor not only deteriorates its efficiency but also impacts the blade fatigue failure. The inlet total Pressure distortion is generated by a 90° bent pipe placed upstream from the inlet. The volute causes the circumferential non-uniform Static Pressure distribution of the impeller Outlet, and the impeller is under the inlet distortion and the non-uniform Outlet distribution condition. Current research pays little attention to the stall inception location and its formation process under the coupling interaction between the bent pipe and volute. In this paper, two installation angles of the inlet bent pipe were compared concerning the stall inception process, including the 115° (M1) and the 295° (M2) models. The circumferential angle between the volute tongue and the elbow axial plane approaches a blade passage width in model M1, and model M2 has the opposite installation angle to M1. The model M1 inlet low total Pressure region caused by the bent pipe, and the Outlet high Static Pressure region induced by the volute tongue together affect the same impeller passage at the 115° location causing the leading edge spillover. The coupling effect of the Model M1 accelerates the process of stall. However, the low total Pressure region for the model M2 is located at the circumferential 295° point, and the high Static Outlet Pressure affects the 115° impellers, resulting in a different stall inception location and process compared to the model M1. The leading edge spillover first occurs at the 295° location because of inlet distortion, and the second spillover appears at the 115° location due to the reversed propagation of the Outlet high Pressure region induced by the volute tongue. Compared to model M1, the stall formation of model M2 is relatively slow. Meanwhile, because of the recirculation flow, the Static temperature rises sharply and the axial velocity drops significantly at the spillover region during the stall process. These results indicate that the coupling interaction between the low total inlet Pressure and the high Outlet Static Pressure jointly determines the stall inception location and its process at the centrifugal compressor inlet.
