Abstract: According to the actual structure characteristics of oil pump parameters,the three-dimensional geometric model of internal flow field of the pump is established by Proe software and mesh with software ICEM,then the internal flow field of the pump were analyzed using the FLUENT software,considering the oil in the theory of air content,using the power law model to describe the rheological properties of non-newtonian fluid constitutive equation for power-law fluid,the pressure velocity coupling with SIMPLEC scheme,turbulent kinetic energy and dissipation rate using two order upwind discretization.The influence of gas content,fluid properties and flow characteristics of oil trapped inside the pump were analyzed by the numerical calculation,the pressure pulsation in 8 % and 10 % content of air are analyzed.The results show that when the air content is 8 %,the influence of pressure in the trapped oil area is higher,and the pressure fluctuation is greater in the nearer to the trapped oil region.It means the magnitude of the pressure pulsation can be expressed as T₁<T₂<T₄<T₃ at the outlet section of the trapped oil area, at the inlet section of the trapped oil area, T₁₁<T₈<T₁₀<T₉. For the trapped oil area,the peak value of the pressure fluctuation in a gear rotating cycle is equal to the number of teeth,and the main frequency is 0.1 times of the gear meshing frequency.The greater the gas content in the trapped oil zone,the smaller the amplitude of the pressure fluctuation.

Key words: engine oil pump, trapped oil area, air content, pressure fluctuation, numerical simulation