Abstract
The objective of this paper is to design development sliding plain bearings for hermetic screw-compressors. In screw-compressors, ball-bearings are widely used to support thrust-loads and radial-loads. This paper studies, the bearing of the screw-compressor is the question of bearing-life and bearing-noise, as to replace the slid-bearings from the ball-bearings. However, difficulties that as the bearings are forced to be refrigerant by diluted oil into lubricated, whose viscosity is much lower than a pure-lubrication. Also the screw-rotor rotates into both direction, clockwise rotational and counter clockwise rotational, depending on the compressor-cycle conditions. On this paper, the experiments were conducted on the compound of the grooved-thrust-bearings by use of refrigerant-blended lubricant simulation system of real conditions, and the tests results in bi-rotational was presented. Tests were conducted on the thrust-bearing tester driven by a motor in simulated refrigerant cycle. The configurations of the test runner and bearing are shown in Figure1. This configuration of the bearing is named 'The Ribbon-Bearing-type' and is calling. At starting period, injection lubrication is applied to reduce friction-torque. The outer and inner diameters of the bearing are φ80 mm and φ40 mm respectively. Combination grooves, spiral and radial ones, are formed on the runner surface. The depth of the each grooves are 0.1 mm. The inflow type spiral-grooves enhance the generation of hydrodynamic pressure as usual way in clockwise rotation. Radial-grooves at the inner periphery are intended to effectively introduce hydrostatic pressure, generated by screw-compressor. The tests were carried out to obtain the data for bearing performance operating at an actual condition of refrigerant-blended lubricant. Film-thickness, bearing-temperatures and friction-torque were measured. Synthetic-oil was used as the lubricant. The tests were carried using refrigerant-blended-lubricant. Refrigerant-blended-lubricant is blending-ratio of 6wt%, 10wt% and 44wt%. Simulate is the real state of the refrigerator-compressor. Bearing-film thickness, bearing-temperature, and friction-torque were measured to evaluate bearing performance. The operating conditions were 2500rpm rotational speed and 3.8kN bearing-load. At that condition using 44wt% refrigerant-blended-lubricant, frictional-torque was about 16Nm. The potential of the ribbon-type-bearings were well demonstrated.
