Study On Pressure Fluctuation Characteristic And Control Of Regenerative Pump For Fuel System

Regenerative pumps,a kind of vane pumps with low specific speed,have the super-low specific speed that beyond the reach of normal centrifugal pumps and they have self-absorbing capacity and cavitation resistance performance.Regenerative pumps also have the advantages of the small size,easy processing and low pressure fluctuations compared with positive displacement pumps.Therefore,in auto industry,regenerative pumps have become popular as the fuel pumps of fuel system for automobiles.Nowadays,with the development of the modern auto industry,the NVH(Noise,Vibration,Harshness)performance improvement has been a key problem demanding prompt solution for the auto-parts suppliers,especially for fuel pump,one of the key auto-parts.In this thesis,in order to improve the NVH performance of the fuel pumps,the inner flow field and pressure fluctuation characteristics and its control of the regenerative pump for fuel system were studied and the structure improvement scheme of pressure fluctuation reduction was proposed.This thesis mainly focuses on the following aspects:(1)The 3D computational model of the new structure regenerative pump with axial inlet and outlet and floating impeller was studied using the steady CFD analysis to estimate the performance of the pump.The accurate of CFD analysis was verified by multiple sets of tests.The characteristics of the inner flow field were discussed to summarize the momentum exchange mechanism and the cause of energy loss of the pump.(2)The unsteady inner flow and pressure fluctuation of regenerative pump computational model under different working conditions were studied in time and frequency domain using unsteady CFD analyses.The pressure fluctuation frequency-domain characteristics and generating mechanism was revealed.The interaction between the rotating blades and two sides of the stripper is the main factor of the pressure fluctuation strength.The noise tests of the fuel pump core were conducted and the strong relativity between the pressure fluctuation and mid-high frequency noise was revealed.The blade passing frequencies and the peak frequencies of noise showed full correspondence,which indicates that the pressure fluctuation reduction of inner field in axial regenerative pump is the effective means to improve the NVH performance of fuel pump.(3)The effect of flow passage structure on pressure fluctuation of axial regenerative pump was analyzed.The regenerative pump with different arc length of stripper,blade numbers and blade profiles were studied to provide a flow passage structure improvement scheme for pressure fluctuation reduction.(4)The pressure fluctuation characteristics and the fluctuation modulation and control effect of regenerative pump with random blade uneven distribution impeller were studied with method of the theoretical analyses and CFD analyses.The random blade distribution method can remarkably decrease pressure fluctuation of blade passing frequency by dispersing the pressure fluctuation strength.An improved design method of the uneven blade distribution impeller was also developed.(5)The pressure fluctuation frequency-domain characteristics and fluctuation modulation and control effect of random blade uneven distribution impellers with different non-uniform degrees and different arc length of stripper were analyzed.It indicates that the moderate large non-uniform degrees and arc length can better reduce the pressure fluctuation.At last,a solution of uneven impeller for pressure fluctuation peak value reduction was put forward.The noise test of the solution showed that the mid-high frequency noises were controlled remarkably and the noise reduction effect was obvious.The feasibility of the solution to improve the NVH performance of fuel pump was verified by the noise test.The inner flow field characteristics,energy momentum mechanism,pressure fluctuation generating mechanism and pressure fluctuation frequency-domain characteristics of regenerative pump were revealed.To reduce the pressure fluctuation of regenerative pump can improve the NVH performance of fuel pump.The solution to pressure fluctuation reduction and frequency spectrum control was put forward from the aspects of flow passage structure and blade distribution.The noise tests of fuel pumps before and after improvement were conducted.Results showed that the solution of flow passage structure and blade distribution can significantly reduce the pressure fluctuation and improve the NVH performance of fuel pump.The consequences of this thesis provide reference for pressure fluctuation reduction and NVH performance improvement of regenerative pump and other multi-blade fluid machinery.