Simulation Study On Back Pressure Chamber System Of Double Vortex Compressor

Since the beginning of the 21 st century,with the continuous improvement of the scroll machinery theory,scroll compressors have been widely used in refrigeration and air conditioning,vacuum pumps,internal energy machines and various gas compression and other fields.Due to changes in market orientation,scroll compressors at this stage are constantly developing in the direction of atmospheric volume and high efficiency.The double vortex compressor with the advantages of large displacement,good scroll force characteristics and small geometric dimensions of the moving and stationary scrolls is undoubtedly favored by people.The large balance iron of the scroll compressor is usually limited by the structural size of the whole machine and the critical speed conditions,and can only run in the back pressure chamber filled with lubricating oil.This will not only change the flow field in the back pressure chamber and affect the balance of the axial force,but also cause the balance iron to receive a large resistance torque when it rotates in the back pressure chamber.Therefore,it is of great significance to explore the process of the rotation of the balance iron in the back pressure chamber filled with lubricating oil for improving the performance of the scroll compressor.In this paper,the double vortex compressor prototype developed by the research group is used as the basic model,and the combination of theoretical calculation and numerical simulation method is used to simulate the back pressure chamber of its important cavity.The optimized design has certain reference value.Firstly,the geometric model of the back pressure chamber system is established according to the prototype.The unsteady process of the balance iron rotating in the back pressure chamber was simulated by FLUENT sliding mesh technology with variable speed and different inlet pipe pressure conditions as variables.By analyzing the velocity nephograms and streamline diagrams on different radial auxiliary surfaces,it is found that the maximum velocity of the flow field inside the back pressure chamber increases with the increase of the main shaft speed,but the change of the inlet pipe pressure has little effect on it;When the spindle speed is small,obvious vortices appear,which gradually decrease and disappear with the increase of the speed.When the spindle speed and different inlet pipe pressures increase,the circulation speed of the lubricating oil flow in the back pressure chamber will be accelerated.Then,the axial force on the mobile scroll under double vortex compression is calculated,and the axial balance force provided by the back pressure chamber is analyzed.It is found that the fluctuation of the axial force on the mobile scroll is too large.In view of this problem,a dislocation optimization method is proposed,which can reduce the axial resultant force range of the movable scroll by up to 28.05%,which greatly improves the axial force of the movable scroll.Finally,in view of the problem that the balance iron of the fan-shaped end face right-angle structure will be subject to a large resistance moment when rotating in the back pressure chamber,an optimization model of the airfoil-type balance iron is proposed.The optimized model makes the streamline trajectory distribution on the radial auxiliary surface more uniform and orderly,the boundary layer separation loss is reduced,and the total resistance torque it receives can be reduced by up to 32.9%.