Leakage Transient Flow Field Characteristics Of Oil-free Scroll Compressor For Fuel Cell

Oil-free scroll air compressor is an ideal device for vehicle fuel cell cathode gas supply system,which can effectively improve the power density and efficiency of the battery,so as to achieve higher energy conversion efficiency.Due to the requirement of no oil lubrication and sealing in the working process,the leakage problem of unsteady compressible flow inside the working chamber is relatively serious,which obstructed the flow field distribution inside the working chamber,and the internal flow loss and heat transfer and other factors greatly limit the play of the compression performance.In order to understand the influence mechanism of the above problems,this paper analyzes the internal leakage of vortex air compressor and calculates the MATLAB programming,and obtains relatively accurate geometric and thermal parameters.The influence of leakage clearance and working speed on the distribution and performance of the flow field in the working chamber of the oil-free scroll air compressor is studied.According to the different formation mechanism and flow characteristics of radial leakage and tangential leakage,the characteristics of radial leakage and tangential leakage under different clearance working conditions were analyzed,the numerical calculation model of tangential leakage and radial leakage was established,and the structured grid model division method of clearance fluid domain was proposed.The transient flow process during the whole working cycle was studied by numerical simulation.The characteristics of the transient flow field in the working cavity and the influence of clearance variation on the distribution of leakage flow and flow field in the working cavity are obtained.The results show that the leakage flow has great influence on the performance parameters of scroll air compressor,such as exhaust flow rate,exhaust temperature and volumetric efficiency.The influence of tangential leakage on the flow field distribution is mainly concentrated in the downstream area of the compression chamber.The gas flow velocity is fast in the meshing gap,and the temperature distribution is very uneven,but the influence on the pressure distribution is small.The influence of radial leakage on the flow field distribution is mainly concentrated in the local region of the clearance fluid domain.The leakage flow flows from the high-pressure cavity to the low-pressure cavity through the axial clearance.The pressure,temperature and velocity are diffusively flowing,and the gradient changes are obvious.In order to explore the characteristics of the influence of rotational speed on leakage flow,the fluid flow process in the cavity of vortex air compressor was simulated under different rotational speed conditions,and many flow field information about the evolution of velocity field,pressure field and temperature field in the cavity were obtained,as well as the characteristic curves of vortex air compressor.The results show that the rotational speed has a great influence on the intake of gas in the suction chamber.Meanwhile,the leakage time and radial clearance of gas in the suction chamber change with the rotational speed,which has a great influence on the amount of gas leakage,leading to the change of flow field distribution characteristics and working performance.Under the unit crank Angle,the tangential leakage line length remains constant.The faster the rotational speed,the shorter the gas leakage time through the radial clearance.However,the higher the density of the leaking gas flow,the gas leakage has different influence characteristics.