Study On Aerodynamic Performance Optimization Of Centrifugal Air Compressor For Hydrogen Fuel Cell Vehicle

To solve the problems of energy shortage and exhaust pollution of traditional vehicles,it is urgent to develop energy-saving and environmental friendly vehicle power source.Compared with traditional internal combustion engines,hydrogen fuel cell(HFC)has the advantages of low pollution and high energy conversion rate.It is one of the most ideal power sources for vehicles.The centrifugal air compressor is the mainstream type of air compressor for hydrogen fuel cell vehicles.It provides air with a certain pressure ratio and flow for the fuel cell system,and its working characteristics affect the performance of the HFC.To improve the working performance of fuel cell system,a vehicle centrifugal air compressor with high efficiency and wide working range is designed for a 100 kW fuel cell system.The main research contents of this paper are as follows:1)According to the working conditions of hydrogen fuel cell system,a singlestage centrifugal air compressor with vane diffuser is designed.The fluid domain of centrifugal air compressor is numerically simulated,and the performance curve of air compressor at design speed is obtained.The simulation results show that the designed prototype meets the requirements of system design conditions.Through the analysis of the cloud picture of the flow field,the shortcomings of the initial model of the air compressor are pointed out,which provides the direction for the subsequent optimization research.2)The effects of impeller blade outlet installation angle,outlet width and blade number on the aerodynamic performance of centrifugal air compressor are studied.Taking the optimal design point efficiency as the goal,the impeller is optimized.The simulation results show that after optimization,the design point efficiency of the air compressor is increased from 73.89% to 75.18%,the power required at the design point is reduced from 24.87 kW to 23.58 kW,and the surge margin is increased by 6%,which effectively improves the aerodynamic performance of the air compressor.3)The effects of diffuser blade outlet diameter,inlet installation angle and blade number on the aerodynamic performance of air compressor are studied,and the optimal value range of each parameter is determined.The idea of optimizing the vane diffuser based on the optimal value range of throat area is put forward.The results show that the optimized diffuser improves the design point efficiency of the air compressor from75.18% to 76.45%,and the surge margin from 49.3% to 50.7%,which proves the feasibility of the optimization method.4)The centrifugal air compressor aerodynamic performance experiment is completed.The design point pressure ratio of the air compressor is 3.22,and the working range at full speed is 17.1～173.6g/s.The air compressor performance curve between rotational speed 30～95krpm is plotted.The experiment curves are close to the simulation curves,and the errors are acceptable,which verifies the accuracy of the numerical simulation and analysis results.After the process of theoretical design,performance simulation and experimental research,the aerodynamic performance of centrifugal air compressor for hydrogen fuel cell vehicle is studied and optimized.The optimal value ranges of studied parameters are summarized,hence the optimized air compressor has higher aerodynamic performance.The simulation method is verified by the experiment.The designed air compressor meets the fuel cell system requirements,and guiding significance and practical value are provided for future studies.