Study On Two Phase Oil Film Lubrication Characteristics Of Meshing Pair Of Single Screw Compressor

Single screw compressor is widely used in energy,construction,metallurgy,refrigeration and other fields because of its advantages of balanced rotor force,no clearance volume,high speed and light load,few parts and easy assembly and maintenance.However,the meshing pair of single screw compressor is easy to wear,which leads to the rapid decline of exhaust volume.This defect has become the biggest bottleneck restricting the development of single screw compressor.Therefore,in this paper,a single screw compressor with 12 m3·min-1 displacement is taken as a prototype,and the two-phase oil film lubrication characteristics of the meshing pair are studied by experiment and numerical simulation.This paper analyzes the working process of single screw compressor,introduces the main geometric parameters selection criteria and the single-line envelope profile design method as well.According to the two-phase flow characteristics of lubricating oil between the meshing pair,the calculation model of circumferential oil film force of a tooth and the calculation model of multi-tooth coupling circumferential moment of single-line enveloping meshing pair are established.In this paper,a two-phase oil film lubrication performance experimental platform for the meshing pair of single screw compressor is built.Based on the actual size of the real machine,the experimental teeth with single-line enveloping profile,single cylindrical enveloping profile and two cylindrical enveloping profile are designed.This experiment includes variable rotor speed experiment,variable inlet gas volume fraction experiment and variable tooth side envelope surface experiment.The results show that:when the rotor speed is 600 r-min-1 and 1000 r-min-1,the experimental research and numerical calculation of two-phase oil film pressure are carried out.The results show that:the higher the rotor speed is,the larger the peak value of two-phase oil film pressure measured by star-wheel is,and the larger the area of high-pressure two-phase oil film pressure action area in the meshing pair clearance is,It shows that the greater the rotor speed is,the more obvious the hydrodynamic pressure of the two-phase oil film is;The two-phase oil film bearing capacity of the two cylindrical teeth is the largest,followed by the single cylindrical tooth,and the last is the single straight tooth.In this paper,the numerical simulation results are compared with the experimental results.The results show that the relative error of the peak pressure of the two-phase oil film on the tooth side of the three profiles is less than 14.1%,which indicates that the mathematical model of the oil film flow field in the meshing pair gap established in this paper is correct and the calculation accuracy meets the requirements.The numerical calculation method can be used to simulate and analyze the two-phase oil film flow field in the meshing pair of single screw compressor.In this paper,the two-phase oil film flow field of meshing pair in the actual meshing process of single screw compressor is numerically simulated.By changing the pressure and gas content at the inlet of the oil film flow field,the oil film flow field of the meshing section of star-wheel teeth at different star-wheel angles and the stress characteristics of star-wheel tooth surface are obtained.The numerical simulation results are included in the calculation model of single tooth circumferential force,and the circumferential torque on single tooth of star-wheel is obtained.According to the spatial distribution characteristics of star-wheel teeth,the circumferential torque of single wheel is coupled by multiple teeth,and the two-phase oil film combined torque of star-wheel is obtained.The results show that the total two-phase oil film resultant moment of the planetary wheel in a complete meshing process is periodically distributed and is negative,which indicates that the oil film moment in front of the wheel is in the main position during the whole meshing process leading position.The calculation results of oil film flow field with different inlet gas content show that the maximum comprehensive torque of two-phase oil film is-8.35 N-m when the gas volume fraction is 20%,the maximum comprehensive torque of two-phase oil film is-8.19 N-m when the gas volume fraction is 40%,the maximum comprehensive torque of two-phase oil film is-7.73 N-m when the gas volume fraction is 60%,and the minimum torque of two-phase oil film is-7.24 N-m under pure oil condition.It shows that when a small amount of gas is added into the lubricating oil,the viscosity of the lubricating oil increases,the oil film force increases,the unbalanced torque of the star-wheel teeth increases,and the star-wheel teeth deflect along the torque direction.The results show that the gap width of the meshing pair decreases on the side with less oil film force,which increases the possibility of wear of the planetary wheel tooth surface.