Experimental and Simulated Investigation of Lubrication Characteristics of a Water-Lubricated Bearing in a Single-Screw Compressor

Water-lubricated single-screw compressors (WSSCs) have developed rapidly in recent years because they can supply oil-free compressed air at considerably low costs. However, a major technical obstacle is that the conventional bearing arrangement of a star wheel shaft is prone to wear failure, which makes it difficult for WSSCs to run properly for long periods of time. To solve this problem, a star wheel thrust bearing with new liquid groove was proposed in this paper. Pulsating forces (i.e., bearing forces) acting on a star wheel shaft by compressing air were calculated through the dynamic analysis of the star wheel shaft system. A mathematical model of hydraulic water films in the bearing sliding clearance was established to describe the influence of water injection pressure on water film pressure distribution and its bearing capacity. Lubrication characteristics were compared between two types of hydrostatic thrust bearings (HTBs) with different grooves to illustrate that the new structure is more suitable for WSSCs. The reasonability of the proposed model and simulation results were verified using an axial thrust bearing test rig developed by the authors. In addition, variation parameters of hydrostatic film thickness between the sliding surfaces of the star wheel axial thrust bearing were measured. The results show that the instability of the water film thickness and axial vibration of the star wheel were suppressed, thereby avoiding the contact of solid materials between the end face of the axial thrust bearing. This study provides a structural optimization pattern of star wheel axial thrust bearings used in water-lubricated single-screw compressors.