Performance Analysis And Structure Optimization Of Fuel Cell Hydrogen Circulation Ejector

The proton exchange membrane fuel fell(PEMFC)injection hydrogen circulation system has the advantages of small size,low noise,and no parasitic energy consumption,which has aroused extensive research interests.However,traditional ejector is difficult to meet the demands of variable power operation of PEMFC,and in-depth research is urgently needed.In order to solve this problem,this paper proposes an ejector that automatically adjusts the nozzle exit position(NXP)according to the pressure of the working fluid to adapt the variable working conditions in PEMFC.It is of great importance to the optimization of the PEMFC.The main tasks include:Firstly,an ejector is proposed that can automatically adjust the NXP of the ejector according to the primary pressure.Secondly,the relationship is derived between ejector back pressure and secondary flow pressure.The corresponding secondary flow pressure is calculated according to the variation range of the primary flow pressure and the back pressure.Finally,the variation of entrainment ratio and the internal velocity cloud diagram of the ejector under different working conditions are analyzed.At last,the relationship between the optimal NXP and the working condition is established.The results show that within a certain range,the increasing of primary pressure improve the suction capacity of the secondary fluid.When the pressure is 3bar and NXP=-15.6mm,the entrainment ratio reaches a peak of 2.43.At the same time,numerical analysis is used to obtain the judgment method of the optimal NXP of the ejector under variable operating conditions.This research is helpful for the matching design and optimization of the ejector and the stack under variable operating conditions.