往复式冰箱压缩机曲轴动态特性与轴承润滑计算分析

Numerical Analysis for the Crankshaft's Dynamic Behavior and Bearing Lubrication of Reciprocating Refrigerator Compressor

提出一种往复式冰箱压缩机受动态载荷作用的悬臂曲轴动态特性及其主副滑动轴承油膜厚度的计算分析方法。采用压缩机汽缸内压力变化实测数据,考虑活塞、连杆与曲轴所受气体力和惯性力,建立了曲轴与电机转子横向位移与倾斜动力学方程;采用滑动轴承有限长油膜模型,并用有限元离散化方法数值逼近;观测了过负荷工况寿命试验后曲轴磨损情况,测量了曲轴圆度。对样机的计算分析结果表明:压缩机工作时,曲轴除转动与平移外,倾斜方位也在不断变化,但上部中心基本上在第一象限内,而下部在第三象限,转角为0°时曲轴倾斜最大;额定与过负荷工况下,曲轴与轴承孔上部会发生偏磨,而轴承与轴承孔下端过负荷工况会发生偏磨;增加曲轴直径,主副轴承最大偏心率都会减少,最小油膜厚度明显增加;转速增大会使主轴承油膜厚度减小,而副轴承油膜厚度增加。该结果可为节能环保冰箱压缩机的研发提供参考。

A method to analyze dynamic behavior of cantilever crankshaft and to calculate the oil film thickness of main and sub bearings under dynamic loading of reciprocating refrigerator compressor is proposed. Transversal and tilt displacement dynamic equations for the crankshaft and the motor rotor are built by considering the gas force and inertia force of piston, connecting rod and crankshaft and using the measured data of pressure within the cylinder A finite element （FE） model for the oil film of the finite journal bearing is established by adopting the FE discrete method for numerical approximation. Crankshaft wear is observed and its roundness is measured after the life test under an over load operating condition. The analysis results show that the angle of inclination of crankshaft constantly changes during the operation of compressor, while the upper center is basically in the first quadrant, and the lower is in the third quadrant. The largest crankshaft incline reaches when its rotational angle is 0°. The eccentric wear between crankshaft and the upper bearing hole happens under the rated load and overload conditions, while theeccentric wear between bearing and the lower bearing happens under the overload condition. The oil film thickness of sub bearing increases and the oil film thickness of main bearing decreases when the rotation speed increases.