Research On Noise Characteristics And Optimal Design Of Fuel Cell Centrifugal Air Compressor

Centrifugal air compressors provide constant pressure ratio and air flow for fuel cell air system to ensure stable and efficient operation of fuel cell system.When the air compressor is operating in the low flow condition area,the centrifugal air compressor generates the phenomenon of wheezing.Whistling due to wheezing is an inherent characteristic of centrifugal air compressors.Under low-flow working conditions,the air compressor blades will rotate and stall,which in turn generates airflow separation and leads to abnormal vibration noise of the body,which seriously affects the normal operation of the air compressor.In this paper,a 110krpm/3.94 k W centrifugal air compressor is designed according to the requirements of a fuel cell system.The performance and wheezing characteristics of the air compressor are analyzed by flow field and acoustic simulation,and the reliability of the design is verified by prototype experiments.Through multi-parameter optimization,the stable operation range of the air compressor under low flow conditions is broadened.The main research of the thesis is as follows:(1)Based on the known partial parameters and theoretical empirical equations of the centrifugal air compressor,the mechanical design parameters of the impeller,diffuser and worm housing of the air compressor were obtained by using one-dimensional numerical calculation and CFturbo software calculation.A three-dimensional model of the air compressor was established based on CFturbo.(2)Numerical simulation analysis of air compressor flow field and sound field based on Fluent software.Through the flow field simulation analysis,the performance curve of the air compressor is obtained,and the operating conditions are changed to study the main causes and intrinsic flow characteristics that cause the air compressor to wheeze.The experimental test of the prototype pressure ratio and efficiency performance curves are compared and analyzed with the numerical simulation results to verify the reliability of the designed prototype.The acoustic simulation analysis was performed to obtain the sound pressure level at each monitoring point at different rotational speeds.(3)Based on the results of numerical simulation analysis of air compressor flow field and sound field,the orthogonal experimental method is used to study the effects of blade number,blade thickness and blade outlet installation angle variation on air compressor performance and surge characteristics,and different optimization schemes are designed by selecting pressure ratio and efficiency as optimization indexes,and a comprehensive optimization scheme for air compressor with reduced sound pressure level is proposed.