Study On Dynamic Radial Clearance And Leakage Characteristics Of Rolling Piston Compressor

The leakage of the radial clearance of the rolling piston compressor is one of the most important factors affecting the volumetric efficiency of the compressor.The dynamic change of the radial gap not only affects the leakage characteristics of the gap,but also relates to the cavitation and friction of the radial gap.Therefore,it is of great practical significance to ascertain the change rule of the radial gap of the compressor.In this paper,the radial clearance of the rolling piston compressor is taken as the research object,the main bearing clearance,the eccentric bearing clearance,the reserved radial clearance,the spindle speed,and the exhaust pressure and other factors are considered to calculate the axis trajectory of the spindle and the rolling piston.The relationship between the axis trajectory and the radial clearance is analyzed,and then the theoretical model of the dynamic radial clearance of the rolling piston compressor is established.Then the experiment was used to verify the variation law of radial clearance,and the variation law of radial clearance of rolling piston compressor under different factor levels was obtained.Finally,Fluent is used to substitute the dynamic radial gap into the simulation model,and the leakage angle caused by the change of the radial gap and the rotation angle of the main shaft corresponding to the failure of the oil film are calculated under different factor levels.Compare with the static radial clearance experimental conditions to improve the simulation analysis made by the previous research group,and point out the direction for the subsequent improvement of the compressor.The main work and research contents of this article include the following aspects:(1)Perform dynamic and kinematic analysis on the key components of the compressor.Calculate the working volume and theoretical discharge pressure of the compressor,and discuss the theoretical calculation formula of the compressor radial leakage characteristics and leakage amount.Using the finite difference method and Reynolds boundary conditions,the oil film bearing capacity of the bearing oil film is solved.At the same time,the grid was tested for independence and the relationship between oil film thickness and oil film bearing capacity was analyzed.(2)Model and calculate the dynamic radial clearance of the compressor.Disperse the mass of the compressor main shaft,establish the rotor dynamic equation of the main shaft,and do dimensionless processing.The principle of Newmark-β method to solve the rotor dynamic equation is introduced,and then the axis trajectory of each node is obtained.The relationship between the axis trajectory and the radial gap is analyzed to establish a theoretical model of the radial gap.Using the control variable method,the calculation of dynamic radial clearance changes under the consideration of main bearing clearance,eccentric bearing clearance,reserved radial clearance,spindle speed,and exhaust pressure and other factors.The results show that the factors that affect the radial clearance of the compressor are: reserved radial clearance> eccentric bearing clearance> spindle bearing clearance> exhaust pressure> speed.(3)Carrying out experimental research on observation of dynamic radial clearance.Use the high resolution and high sampling frequency of the high-speed camera to photograph and record the positions of the cylinder and rolling piston at different times.The contours of the cylinder and the rolling piston in the picture are identified by Matlab,and the trajectory of the axial center of the rolling piston and the cylinder is fitted by the least square method,and then the variation law of the radial clearance of the compressor is derived.The results show that the radial gap first decreases and then increases,and it is the smallest at around 110 ° and the largest at around 230 degrees.Moreover,the experimental observations and theoretical calculations show that the radial clearance changes are basically the same.(4)Consider the sealing performance of the radial gap of the compressor under the dynamic change of the radial gap.The two-phase flow simulation model for compressing radial gap was established by Fluent software.The dynamic grid technology and UDF are used to control the variation of radial clearance.The radial gap leakage process and radial oil film breakdown process of the compressor are studied in detail through numerical simulation.The results show that the change in radial clearance leads to an increase in the theoretical leakage of the compressor,and the angle of the main shaft corresponding to the rupture of the radial seal oil film advances.In actual engineering applications,the gap fluctuation should be avoided as much as possible,or the way of spindle offset should be adopted to reduce the occurrence of leakage.