Numerical Simulation Of Transient Flow And Investiogation On The Modifications Of The Scution Flow Passage In A Scroll Compressor

As a new type of positive displacement compressor,scroll compressors becoming one of the main development directions of high performance compressors at present and future,because of their simple structure,lightweight,low energy consumption and high reliability at the same refrigerating capacity in small and medium compressors.Taking a scroll compressor as research object in this paper,an investigation has been conducted to study transient flow characteristics in the suction flow passage of scroll compressor based on three-dimensional unsteady Computational Fluid Dynamics numerical simulations.The factors affecting the volumetric efficiency of scroll compressor are analyzed.The main research contents and conclusions can be summarized as follows:(1)An unsteady numerical simulation model of scroll compressor with double clearance fluid domain was established.The simulation accuracy of numerical model was verified according to the test performance parameters of scroll compressor.The results indicate that the axial clearance has larger influence on the COP,isentropic efficiency and discharge temperature than the flank clearance,while the flank clearance has slightly bigger effect on the volumetric efficiency.(2)Six modification schemes are proposed by enlarging or reducing the volume of the suction flow passage based on a scroll compressor to improve its performance.Both the volumetric efficiency and suction mass flow rate pulsations in compressors with different suction flow passage were studied.The transient flow field distributions characteristics among different flow passage were carried out.The results indicated that the enlargement of the suction passage only improves the volumetric efficiency a little while the shrink of the passage can improve it effectively.The volume variation of flow passage due to the movement of orbiting scroll leads to the mass flow rate fluctuation.The volumetric efficiency increases and the mass flow rate pulsation decreases with the modification meshing angle among the tight modification schemes.(3)Both the operating characteristic and gas forces and moments exerted on the orbiting scroll in asymmetric suction structure scroll compressor were investigated.The results show that the volumetric efficiency of the asymmetric suction scheme is 14.8%higher than the original one and its suction pulsation intensity is the lowest.But its indicated power increases a lot due to the large discharge loss and additional radial leakage loss,which result from the higher built-in volume ratio and pressure in the modified suction chamber.The additional gas forces exerted on the orbiting scroll segments between symmetric working chambers is the main reason causing the increase of total gas forces in asymmetric suction scroll compressor.In addition,the spin moment decreases by 71.3%.The reversed spin moments appeared in the operating processes mainly caused by the additional tangential forces in asymmetric scroll compressor.(4)A novel asynchronous discharge structures scroll compressor was proposed.Both the variations of discharge flow pulsation and flow behavior in discharge chamber were analyzed.The results show that the asynchronous discharge structure compressor can improve the isentropic efficiency of asymmetric suction structure scroll compressor effectively.The effect of refrigerant under-compression and backflow caused the complex secondary flow loss in the discharge chamber.The backflow from discharge pipe is the main reason causing the discharge mass flow rate pulsations.The decrease of pressure difference between asymmetrical working chambers effectively reduce the gas forces exerted on the orbiting scroll in asynchronous discharge structure compressor effectively.