A Theoretical Method for Evaluating the Lubrication Performance of the Meshing Pair Profiles in Water Flooded Single Screw Compressors Based on the Micro Deflecting Motion Trajectory

Abstract

To improve the life of the meshing pair in single screw compressor (SSC), several meshing pair profiles (MPP) were proposed for raising the lubrication properties. Therefore, it is necessary to evaluate the lubrication performance of the MPPs. In this paper, an evaluation method based on micro deflecting motion trajectory (MDMT) is proposed and the theoretical model to realize MDMT is established. The model mainly contains a geometric model, a thermodynamics model, a hydrodynamic lubrication model and corresponding algorithm. With the presented method, three kinds of MPP including single straight line type (SSLT), single column type (SCT) and multi column type (MCT) have been analyzed. Obtained results show that compared to the SSLT and SCT, the MCT generates the greatest peak value of the water film pressure. The total torque applied on the gate-rotor generated by the water films decreases with the increment of the discharge pressure and increases with the machine size. The water film stiffness firstly decreases and then increases with the micro deflecting angle increasing. The water film stiffness at trailing side is always larger than that at leading side. As the discharge pressure increases, the MDMT curves approach the leading flank, and the lubrication properties get worse. With the machine size increasing, the MDMT curves move towards the trailing side and the lubrication performance is improved. Comparing to the other two MPPs, the MCT can achieve floating mesh without contact in relatively larger machines and comparably lower discharge pressure.