The experimental investigation of axial-flow pump has been rapidly developed to meet the needs of South-to-North Water Diversion Project of China.Owing to the boundary conditions of hub,blade tip clearance,much of the...The experimental investigation of axial-flow pump has been rapidly developed to meet the needs of South-to-North Water Diversion Project of China.Owing to the boundary conditions of hub,blade tip clearance,much of the physical phenomena and laws involved in this complex flow field can't be fully determined.The flow characteristics of the high efficiency axial-flow pump have been simulated by RNG k-e turbulence model and SIMPLEC arithmetic based on FLUENT software.Numerical results indicate that the data from the prediction show agreement with the experimental results,static pressure on pressure side of blades increases slightly at circumferential direction with radius increasing,and keep almost constant at the same radial while increasing gradually from inlet to exit on the suction side along flow direction at design conditions.The static pressure,total pressure and velocity at inlet,impeller outlet and vane outlet were measured by a five-hole probe,and a contrastive experiment was done to investigate the influence of hub leakage.The experimental results show that inlet flow is almost axial and the prerotation is very small at various conditions.The meridional velocity and circulation distribution are almost identical at impeller outlet at design conditions due to steady flow and high efficiency.The residual circulation exits at downstream of the guide vane,and the circumferential velocity component increases linearly from hub to tip at small flow rate conditions.Hub leakage in adjustable blades results in the decrease of the meridional velocity and circulation at blade exit near hub.The results of numerical simulation and experiments supply important flow structure information for the high-efficiency axial-flow pump.展开更多
As the critical equipment,large axial-flow fan(LAF)is used widely in highway tunnels for ventilating.Note that any malfunction of LAF can cause severe consequences for traffic.Specifically,fault deterioration is suppr...As the critical equipment,large axial-flow fan(LAF)is used widely in highway tunnels for ventilating.Note that any malfunction of LAF can cause severe consequences for traffic.Specifically,fault deterioration is suppressed tremendously when an abnormal state is detected in the stage of early fault.Thus,the monitoring of the early fault characteristics is very difficult because of the low signal amplitude and system disturbance(or noise).In order to overcome this problem,a novel early fault judgment method to predict the operation trend is proposed in this paper.The vibration-electric information fusion,the support vector machine(SVM)with particle swarm optimization(PSO),and the cross-validation(CV)for predicting LAF operation states are proposed and discussed.Finally,the results of the experimental study verify that the performance of the proposed method is superior to that of the contrast models.展开更多
Airfoil is the element of fan blade design. It is strongly anticipated to design a fan of ave- raged high performance over a wide operation range. Multi-point optimization design of airfoil for axial flow fan was prop...Airfoil is the element of fan blade design. It is strongly anticipated to design a fan of ave- raged high performance over a wide operation range. Multi-point optimization design of airfoil for axial flow fan was proposed over specific operation range. Weighted objective function of airfoil lift-drag ratio was constructed for several operation points around the designing one. Airfoil was defined by parametric B-spline curve of limited shape controlling points. Results show that normal standard airfoils have remained spaces to be optimized under specific operation conditions. Airfoil performance is sensitive to flow′s Reynolds number and cascade solidity. Predicting flow transition along airfoil profile is essential to search for optimized one. Optimized airfoil of wide operation range is possible to obtain with prescribed fitness function. Obtainments of multi-point optimization may be relatively lower at design point, but positive obtainments are achieved at off-design ones. Resulted airfoil is specially suitable for axial flow fans operating frequently at off-design point such as air condition coolers.展开更多
Accurate and efficient prediction of the aerodynamic performance and flow details of axial-flow com-pressors is of great engineering application value for the aerodynamic design and flow control of axial-flow compres-...Accurate and efficient prediction of the aerodynamic performance and flow details of axial-flow com-pressors is of great engineering application value for the aerodynamic design and flow control of axial-flow compres-sors.In this work,a delayed detached eddy simulation method is developed and applied to numerically simulate the tur-bulent channel flow and the aerodynamic performance of NASA Rotor 35.Several acceleration techniques including parallel implementation are also used to speed up the iteration convergence.The mean velocity distribution and Reyn-olds stress distribution in the boundary layer of turbulent channel flow and the aerodynamic performance curve of NASA Rotor 35 are predicted.The good agreement between the present delayed detached eddy simulation results and the available direct numerical simulation results or experimental data confirms the effectiveness of the developed meth-od in the accurate and efficient prediction of complex flow in turbomachinery.展开更多
Post stall behaviors of a single stage compression system are studied theoretically and experimentally in this paper. A one dimensional nonlinear model, which is able to describe the dynamically post stall behavio...Post stall behaviors of a single stage compression system are studied theoretically and experimentally in this paper. A one dimensional nonlinear model, which is able to describe the dynamically post stall behaviors of the compression system, is applied to simulate the post stall behaviors digitally. The stall types, i.e. , rotating stall and surge, are determined. The variations of annular average parameters while the compression system goes into stall are also calculated exactly. The post stall behaviors are measured on the single stage compressor test rig. The measurement shows that rotating stall and surge appear under different conditions. On the basis of experiments, it is found that the post stall behaviors are influenced remarkably by some factors, such as rotation speeds, construction type and size of the exhaust duct. Good agreement between the simulation and experiments proves that this modeling technique is valid for simulating the post stall behaviors.展开更多
Throughflow design has the advantages of less time consumption and large optimization space,and thus is the corner stone of advanced design system of multi-stage axial-flow compressors.The majority of relevant studies...Throughflow design has the advantages of less time consumption and large optimization space,and thus is the corner stone of advanced design system of multi-stage axial-flow compressors.The majority of relevant studies were limited to the throughflow inverse designs,and quite few works have been till now devoted to the throughflow optimal designs.In this work,an automatic and rapid throughflow-based optimal design method is proposed for axial-flow compressors in which a throughflow inverse design solver is embedded in optimal genetic algorithm to improve the design efficiency of axial-flow compressor.Two types of design parameters in the throughflow inverse design of axial-flow compressors,i.e.,swirl and shroud curve,are simultaneously used to optimize both the blade shape and flow path.The proposed method is validated by the redesign optimization of the benchmark axial-flow compressor NASA Stage 35,and the CFD predictions show that the throughflow-based optimization leads to 1.18% efficiency benefit at design condition.The proposed method is then utilized to the two-dimensional throughflow optimal design of a large-scale 6.5-stage axial-flow industrial compressor.The optimal design results are confirmed by CFD predictions,indicating that the proposed method can effectively improve the design adiabatic efficiency of the compressors by 1.09% within a few minutes on desk-top computer.Two throughflow design implications are also obtained for advanced axial-flow industrial compressors.This work could enhance the capability of throughflow design method and has engineering application value to explore the throughflow optimization space of multi-stage axial-flow compressors.展开更多
Axial flow pumps are widely used in water conservancy,petrochemical and agricultural industries.Efficient operation is crucial for energy conservation and emission reduction.Improving efficiency under severe condition...Axial flow pumps are widely used in water conservancy,petrochemical and agricultural industries.Efficient operation is crucial for energy conservation and emission reduction.Improving efficiency under severe conditions requires studying the internal flow of axial-flow pumps,particularly at low flow rates where backflow vortices form near the impeller inlet.This study investigates the unsteady flow characteristics of backflow vortices at different flow rates in an axial-flow pump.Results show that backflow vortices form when the flow rate decreases to 0.59Q_(d).As the flow rate further declines,the backflow vortex progresses upstream,contracts,and rebounds.The flow rate range is divided into three stages:Stage Ⅰ with no backflow vortex,stage Ⅱ with initial vortex development extending upstream and relatively fragmented,and stage Ⅲ with vortex contraction and rebound forming a more coherent structure.Besides,backflow vortices induce significant pressure fluctuations and velocity oscillations with the primary frequency being 0.5 fb.They exhibit a three-dimensional spiral motion involving changes in axial length,self-rotation,and revolution around the pump axis,with an angular velocity of approximately half the impeller’s rotational speed.This work enhances insights into backflow vortex behaviors,which is essential for optimizing pump design and improving operational stability in challenging environments.展开更多
The three-dimensional unsteady turbulent flow in axial-flow pumps was simulated based on Navier-Stoke solver embedded with k - ε RNG turbulence model and SIMPLEC algorithm. Numerical results show that the unsteady pr...The three-dimensional unsteady turbulent flow in axial-flow pumps was simulated based on Navier-Stoke solver embedded with k - ε RNG turbulence model and SIMPLEC algorithm. Numerical results show that the unsteady prediction results are more accurate than the steady results, and the maximal error of unsteady prediction is only 4.54%. The time-domain spectrums show that the static pressure fluctuation curves at the inlet and outlet of the rotor and the outlet of the stator are periodic, and all have four peaks and four valleys. The pressure fluctuation amplitude increases from the hub to the tip at the inlet and outlet of the rotor, but decreases at the outlet of the stator. The pressure fluctuation amplitude is the greatest at the inlet of the rotor, and the average amplitude decreases sharply from the inlet to the outlet. The frequency spectrums obtained by Fast Fourier Transform （FFT） show that the dominant frequency is approximately equal to the blade passing frequency. The static pressure on the pressure side of hydrofoil on different stream surfaces remains almost consistent, and increases gradually from the blade inlet to the exit on the suction side at different time steps. The axial velocity distribution is periodic and is affected by the stator blade number at the rotor exit. The experimental results show that the flow is almost axial and the pre-rotation is very small at the rotor inlet under the conditions of 0.8 QN -1.2 QN Due to the clearance leakage, the pressure, circulation and meridional velocity at the rotor outlet all decrease near the hub leakage and tip clearance regions.展开更多
The interaction of flow through the inducer and impeller of an axial-flow pump equipped with an inducer has significant effect on its performance. This article presents a recent numerical investigation on this topic. ...The interaction of flow through the inducer and impeller of an axial-flow pump equipped with an inducer has significant effect on its performance. This article presents a recent numerical investigation on this topic. The studied pump has an inducer with 3 blades mounted on a conical hub and a 6-blade impeller. The blade angle of the impeller is adjustable to generate different relative circumferential angles between the inducer blade trailing edge and the impeller blade leading edge. A computational fluid dynamics code was used to investigate the flow characteristics and performance of the axial-flow pump. For turbulence closure, the RNG k-ε model was applied with an unstructured grid system. The rotor-stator interaction was treated with a Multiple Reference Frame （MRF） strategy. Computations were performed in different cases： 7 different relative circumferential angles （ Δθ ） between the inducer blade trailing edge and the impeller blade leading edge, and 3 different axial gaps （G） between the inducer and the impeller. The variation of the hydraulic loss in the rotator was obtained by changing Δθ . The numerical results show that the pressure generated is minimum in the case of （ G = 3%D）, which indicates that the interference between inducer and impeller is strong if the axial gap is small. The pump performances were predicted and compared to the experimental measurements. Recommendations for future modifications and improvements to the pump design were also given.展开更多
In this paper, the cavitating flow within a slanted axial-flow pump is numerically researched. The hydraulic and cavitation performance of the slanted axial-flow pump under different operation conditions are estimated...In this paper, the cavitating flow within a slanted axial-flow pump is numerically researched. The hydraulic and cavitation performance of the slanted axial-flow pump under different operation conditions are estimated. Compared with the experimental hydraulic performance curves, the numerical results show that the filter-based model is better than the standard k-ε model to predict the parameters of hydraulic performancE. In cavitation simulation, compared with the experimental results, the proposed numerical method has good predicting ability. Under different cavitation conditions, the internal cavitating flow fields within slanted axial-flow pump are investigated. Compared with flow visualization results, the major internal flow features can be effectively grasped. In order to explore the origin of the cavitation performance breakdown, the Boundary Vorticity Flux （BVF） is introduced to diagnose the cavitating flow fields. The analysis results indicate that the cavitation performance drop is relevant to the instability of cavitating flow on the blade suction surface.展开更多
基金supported by National Hi-tech Research and Development Program of China(863 Program,Grant No.2007AA05Z207)National Science and Technology Support Scheme of China(Grant No.2008BAF34B10)Jiangsu Provincial Graduate Student Innovation Foundation of China(Grant No.CX08B_064Z)
文摘The experimental investigation of axial-flow pump has been rapidly developed to meet the needs of South-to-North Water Diversion Project of China.Owing to the boundary conditions of hub,blade tip clearance,much of the physical phenomena and laws involved in this complex flow field can't be fully determined.The flow characteristics of the high efficiency axial-flow pump have been simulated by RNG k-e turbulence model and SIMPLEC arithmetic based on FLUENT software.Numerical results indicate that the data from the prediction show agreement with the experimental results,static pressure on pressure side of blades increases slightly at circumferential direction with radius increasing,and keep almost constant at the same radial while increasing gradually from inlet to exit on the suction side along flow direction at design conditions.The static pressure,total pressure and velocity at inlet,impeller outlet and vane outlet were measured by a five-hole probe,and a contrastive experiment was done to investigate the influence of hub leakage.The experimental results show that inlet flow is almost axial and the prerotation is very small at various conditions.The meridional velocity and circulation distribution are almost identical at impeller outlet at design conditions due to steady flow and high efficiency.The residual circulation exits at downstream of the guide vane,and the circumferential velocity component increases linearly from hub to tip at small flow rate conditions.Hub leakage in adjustable blades results in the decrease of the meridional velocity and circulation at blade exit near hub.The results of numerical simulation and experiments supply important flow structure information for the high-efficiency axial-flow pump.
基金Project(2018YFB2002100)supported by the National Key R&D Program of China。
文摘As the critical equipment,large axial-flow fan(LAF)is used widely in highway tunnels for ventilating.Note that any malfunction of LAF can cause severe consequences for traffic.Specifically,fault deterioration is suppressed tremendously when an abnormal state is detected in the stage of early fault.Thus,the monitoring of the early fault characteristics is very difficult because of the low signal amplitude and system disturbance(or noise).In order to overcome this problem,a novel early fault judgment method to predict the operation trend is proposed in this paper.The vibration-electric information fusion,the support vector machine(SVM)with particle swarm optimization(PSO),and the cross-validation(CV)for predicting LAF operation states are proposed and discussed.Finally,the results of the experimental study verify that the performance of the proposed method is superior to that of the contrast models.
基金Strategic Leading Project of Shanghai Municipal Science Committee(16DZ1121202)
文摘Airfoil is the element of fan blade design. It is strongly anticipated to design a fan of ave- raged high performance over a wide operation range. Multi-point optimization design of airfoil for axial flow fan was proposed over specific operation range. Weighted objective function of airfoil lift-drag ratio was constructed for several operation points around the designing one. Airfoil was defined by parametric B-spline curve of limited shape controlling points. Results show that normal standard airfoils have remained spaces to be optimized under specific operation conditions. Airfoil performance is sensitive to flow′s Reynolds number and cascade solidity. Predicting flow transition along airfoil profile is essential to search for optimized one. Optimized airfoil of wide operation range is possible to obtain with prescribed fitness function. Obtainments of multi-point optimization may be relatively lower at design point, but positive obtainments are achieved at off-design ones. Resulted airfoil is specially suitable for axial flow fans operating frequently at off-design point such as air condition coolers.
基金National Science and Technology Major Project of China(No.2017-II 0006-0020)National Key Research and Development Project of China(2016YFB0200901)National Natural Science Foundation of China(51776154)。
文摘Accurate and efficient prediction of the aerodynamic performance and flow details of axial-flow com-pressors is of great engineering application value for the aerodynamic design and flow control of axial-flow compres-sors.In this work,a delayed detached eddy simulation method is developed and applied to numerically simulate the tur-bulent channel flow and the aerodynamic performance of NASA Rotor 35.Several acceleration techniques including parallel implementation are also used to speed up the iteration convergence.The mean velocity distribution and Reyn-olds stress distribution in the boundary layer of turbulent channel flow and the aerodynamic performance curve of NASA Rotor 35 are predicted.The good agreement between the present delayed detached eddy simulation results and the available direct numerical simulation results or experimental data confirms the effectiveness of the developed meth-od in the accurate and efficient prediction of complex flow in turbomachinery.
文摘Post stall behaviors of a single stage compression system are studied theoretically and experimentally in this paper. A one dimensional nonlinear model, which is able to describe the dynamically post stall behaviors of the compression system, is applied to simulate the post stall behaviors digitally. The stall types, i.e. , rotating stall and surge, are determined. The variations of annular average parameters while the compression system goes into stall are also calculated exactly. The post stall behaviors are measured on the single stage compressor test rig. The measurement shows that rotating stall and surge appear under different conditions. On the basis of experiments, it is found that the post stall behaviors are influenced remarkably by some factors, such as rotation speeds, construction type and size of the exhaust duct. Good agreement between the simulation and experiments proves that this modeling technique is valid for simulating the post stall behaviors.
基金financially supported by the National Science and Technology Major Project of China(Grant No.2017-Ⅱ-0006-0020)National Key Research and Development Project of China(Grant No.2016YFB0200901)+1 种基金National Natural Science Foundation of China(Grant No.51776154)Shaanxi Key Research and Development Project(Grant No.2018KWZ-01)。
文摘Throughflow design has the advantages of less time consumption and large optimization space,and thus is the corner stone of advanced design system of multi-stage axial-flow compressors.The majority of relevant studies were limited to the throughflow inverse designs,and quite few works have been till now devoted to the throughflow optimal designs.In this work,an automatic and rapid throughflow-based optimal design method is proposed for axial-flow compressors in which a throughflow inverse design solver is embedded in optimal genetic algorithm to improve the design efficiency of axial-flow compressor.Two types of design parameters in the throughflow inverse design of axial-flow compressors,i.e.,swirl and shroud curve,are simultaneously used to optimize both the blade shape and flow path.The proposed method is validated by the redesign optimization of the benchmark axial-flow compressor NASA Stage 35,and the CFD predictions show that the throughflow-based optimization leads to 1.18% efficiency benefit at design condition.The proposed method is then utilized to the two-dimensional throughflow optimal design of a large-scale 6.5-stage axial-flow industrial compressor.The optimal design results are confirmed by CFD predictions,indicating that the proposed method can effectively improve the design adiabatic efficiency of the compressors by 1.09% within a few minutes on desk-top computer.Two throughflow design implications are also obtained for advanced axial-flow industrial compressors.This work could enhance the capability of throughflow design method and has engineering application value to explore the throughflow optimization space of multi-stage axial-flow compressors.
基金Project supported by the National Natural Science Foundation of China(Grant No.U22B6010)supported by the International Partnership Program of Chinese Academy of Sciences(Grant No.025GJHZ2022118FN)the Hainan Provincial Joint Project of Sanya Yazhou Bay Science and Technology City(Grant No.2021CXLH0003).
文摘Axial flow pumps are widely used in water conservancy,petrochemical and agricultural industries.Efficient operation is crucial for energy conservation and emission reduction.Improving efficiency under severe conditions requires studying the internal flow of axial-flow pumps,particularly at low flow rates where backflow vortices form near the impeller inlet.This study investigates the unsteady flow characteristics of backflow vortices at different flow rates in an axial-flow pump.Results show that backflow vortices form when the flow rate decreases to 0.59Q_(d).As the flow rate further declines,the backflow vortex progresses upstream,contracts,and rebounds.The flow rate range is divided into three stages:Stage Ⅰ with no backflow vortex,stage Ⅱ with initial vortex development extending upstream and relatively fragmented,and stage Ⅲ with vortex contraction and rebound forming a more coherent structure.Besides,backflow vortices induce significant pressure fluctuations and velocity oscillations with the primary frequency being 0.5 fb.They exhibit a three-dimensional spiral motion involving changes in axial length,self-rotation,and revolution around the pump axis,with an angular velocity of approximately half the impeller’s rotational speed.This work enhances insights into backflow vortex behaviors,which is essential for optimizing pump design and improving operational stability in challenging environments.
基金Project supported by the National High Technology Research and Development Program of China (863 Program,Grant No.2007AA05Z207)the Graduate Student Innovation Foundation of Jiangsu Province (Grant No.CX08B_064Z)the National Science and Technology Support Program (Grant No.2008BAF34B15)
文摘The three-dimensional unsteady turbulent flow in axial-flow pumps was simulated based on Navier-Stoke solver embedded with k - ε RNG turbulence model and SIMPLEC algorithm. Numerical results show that the unsteady prediction results are more accurate than the steady results, and the maximal error of unsteady prediction is only 4.54%. The time-domain spectrums show that the static pressure fluctuation curves at the inlet and outlet of the rotor and the outlet of the stator are periodic, and all have four peaks and four valleys. The pressure fluctuation amplitude increases from the hub to the tip at the inlet and outlet of the rotor, but decreases at the outlet of the stator. The pressure fluctuation amplitude is the greatest at the inlet of the rotor, and the average amplitude decreases sharply from the inlet to the outlet. The frequency spectrums obtained by Fast Fourier Transform （FFT） show that the dominant frequency is approximately equal to the blade passing frequency. The static pressure on the pressure side of hydrofoil on different stream surfaces remains almost consistent, and increases gradually from the blade inlet to the exit on the suction side at different time steps. The axial velocity distribution is periodic and is affected by the stator blade number at the rotor exit. The experimental results show that the flow is almost axial and the pre-rotation is very small at the rotor inlet under the conditions of 0.8 QN -1.2 QN Due to the clearance leakage, the pressure, circulation and meridional velocity at the rotor outlet all decrease near the hub leakage and tip clearance regions.
基金the National Nature Science Foundation of China (Grant No. 90510007) Beijing Nature Science Foundation of China (Grant No. 3071002)the National Key Technology R and D Program (Grant No. 2006BAD11B07).
文摘The interaction of flow through the inducer and impeller of an axial-flow pump equipped with an inducer has significant effect on its performance. This article presents a recent numerical investigation on this topic. The studied pump has an inducer with 3 blades mounted on a conical hub and a 6-blade impeller. The blade angle of the impeller is adjustable to generate different relative circumferential angles between the inducer blade trailing edge and the impeller blade leading edge. A computational fluid dynamics code was used to investigate the flow characteristics and performance of the axial-flow pump. For turbulence closure, the RNG k-ε model was applied with an unstructured grid system. The rotor-stator interaction was treated with a Multiple Reference Frame （MRF） strategy. Computations were performed in different cases： 7 different relative circumferential angles （ Δθ ） between the inducer blade trailing edge and the impeller blade leading edge, and 3 different axial gaps （G） between the inducer and the impeller. The variation of the hydraulic loss in the rotator was obtained by changing Δθ . The numerical results show that the pressure generated is minimum in the case of （ G = 3%D）, which indicates that the interference between inducer and impeller is strong if the axial gap is small. The pump performances were predicted and compared to the experimental measurements. Recommendations for future modifications and improvements to the pump design were also given.
基金Project supported by the Key Research Projects of Shanghai Science and Technology Commission(GrantNo.10100500200)the Science and Technology Plan of Zhejiang Province(Grant No.2011C11068)the Shanghai Program for Innovative Research Team in Universities
文摘In this paper, the cavitating flow within a slanted axial-flow pump is numerically researched. The hydraulic and cavitation performance of the slanted axial-flow pump under different operation conditions are estimated. Compared with the experimental hydraulic performance curves, the numerical results show that the filter-based model is better than the standard k-ε model to predict the parameters of hydraulic performancE. In cavitation simulation, compared with the experimental results, the proposed numerical method has good predicting ability. Under different cavitation conditions, the internal cavitating flow fields within slanted axial-flow pump are investigated. Compared with flow visualization results, the major internal flow features can be effectively grasped. In order to explore the origin of the cavitation performance breakdown, the Boundary Vorticity Flux （BVF） is introduced to diagnose the cavitating flow fields. The analysis results indicate that the cavitation performance drop is relevant to the instability of cavitating flow on the blade suction surface.
