Study Of Internal Leakage Characteristics Of Scroll Compressors

As a new generation of positive displacement compressors,scroll compressors are widely used in petrochemical,aerospace,transportation and other fields due to their simple structure,reliable operation,energy saving and environmental protection.In the actual operation of the scroll compressor,there will be different degrees of leakage between the compression chambers.The leakage reduces the volumetric efficiency of the scroll compressor and the energy efficiency of the whole machine.Therefore,it is very important to study the leakage characteristics of the scroll compressor.In this paper,the leakage mathematical model of scroll compressor is taken as the breakthrough point.Through the analysis of leakage flow of fluid medium,the tangential leakage and radial labyrinth seal of scroll compressor are studied by taking oil-gas two-phase flow as the carrier,and the leakage characteristics and flow field distribution are analyzed in depth.Firstly,aiming at the tangential leakage problem of scroll compressor,a tangential leakage fluid domain model considering friction and compressibility is established according to the prototype data.The unsteady numerical simulation of the fluid domain model is carried out by Fluent software,and the influence of different conditions on the tangential leakage characteristics of scroll compressor is analyzed.The results show that the pressure difference and radial clearance have the greatest influence on tangential leakage,and the mass leakage increases with the increase of pressure difference and radial clearance.With the increase of oil and gas mass percentage and tooth surface roughness,the mass leakage decreases gradually.When the oil and gas mass percentage is 12 % and the tooth surface roughness is Ra1.6,the mass leakage is the smallest.Secondly,the leakage characteristics of the radial labyrinth seal of the scroll compressor are studied.By analyzing the influencing factors of the leakage of the labyrinth seal,the structure of the labyrinth groove is optimized.In addition to the rectangular groove,three kinds of labyrinth grooves are designed,and the corresponding three-dimensional model is established.The influence of structural parameters and operating conditions on the leakage characteristics of the radial labyrinth seal is studied by numerical simulation.The results show that the sealing performance of U-groove is the best,followed by V-groove,rectangular groove and trapezoidal groove.Reducing the groove depth and increasing the surface roughness of the tooth bottom are beneficial to the improvement of sealing performance.When the groove depth is 0.1 mm and the surface roughness of the tooth bottom is Ra3.2,the labyrinth seal effect is the best.With the increase of pressure difference and axial clearance,the mass leakage increases gradually and the sealing performance decreases.Finally,the U-groove of radial labyrinth seal is studied.The DPM model is used to calculate the two-way coupling of oil-gas two-phase flow in the U-groove.The influence of oil droplet parameters on the leakage characteristics of radial labyrinth seal and the distribution of oil droplets in the U-groove are studied.The results show that the mass leakage increases with the increase of oil droplet mass fraction and particle size.The capture rate of oil droplets under the Rosin-Rammler model is about85 %.The increase of oil droplet size helps the fluid to produce eddy current dissipation effect in the sealing structure,which improves the sealing performance.The conclusion of this study can provide some reference for the sealing optimization of scroll compressor.