Design And Optimization Of Low Specific Speed Centrifugal Compressor For Fuel Cell System

Fuel cell vehicles have the advantages of high energy conversion efficiency,nonpolluting emissions,and long cruising range,which is important direction for the development of new energy vehicles.The air compressor technology of the fuel cell system is one of the major bottlenecks faced by the fuel cell vehicle's co re component technology and developmentCentrifugal air compressor has the advantages of high efficiency,quick response,etc.It is the focus of the current development of automotive fuel cell air compressors.Centrifugal air compressors have high rotation speeds and need to be driven by high-speed motors.The high cost and high rotational speeds cause lubrication and heat dissipation difficulties.Reducing the speed of the centrifugal compressor through the low specific speed design is one of the important measures and ways to reduce the cost of the centrifugal fuel system for the vehicle fuel cell.Low efficiency and poor performance of non-design conditions are the major difficulties faced by the design of low specific speed centrifugal compressors.In this paper,the one-dimensional simplified model of centrifugal air compressor was used to study the influence of different structural parameters on the non-design conditions and design conditions of low specific speed centrifugal compressors.The numerical simulation was used to calculate the optimal one-dimensional centrifugal air compressor.Aerodynamic performance.The flow field deviation analysis method wa s proposed,and the internal three-dimensional flow of the centrifugal compressor under non-design conditions and design conditions was comparatively studied.It was revealed that large-scale flow separation occurred on the suction surface of the main blade under off-design conditions.The obvious vortex structure at the front of the flow path leading to induction is an important factor that leads to the degraded performance of non-design conditions.The deviation of the pressure distribution on the suction surface of the main blade of the non-design condition and design condition is proposed as the non-design of the centrifugal air compressor.The goal of performance optimization is to use the correlation of pressure arrays under different conditions as an evaluation index.Reducing the pressure distribution deviation is an important means to improve the performance of off-design conditions.Taking the pressure distribution deviation as the optimization goal,different schemes were designed using orthogonal test method.The blade back bend,forward sweep and diffuser length of the centrifugal air compressor were optimized,and the three-dimensional flow field analysis of different schemes was adopted.The mechanism of the influence of the three design paramet ers on the performance of the centrifugal compressor was studied.Compared with the prototype,the optimized air compressor has an efficiency increase of 2% in all operating conditions,a 5% increase in efficiency at low flow conditions,and a slight decrease in pressure ratio but meets the design requirements,verifying the pressure distribution Deviation as the rationality of the optimization goal.