结构参数对增压器浮环轴承润滑特性和环速比的影响

基于以往对增压器的浮环轴承润滑分析中大都忽略浮环的环速比影响,或将润滑性能和环速比独立分析。该文采用数值分析方法研究了增压器浮环轴承的润滑特性和环速比,分析中考虑了转轴、浮环、轴承座之间的传热因素,基于Reynolds方程和浮环平衡方程,建立了浮环轴承润滑模型,对比分析了浮环内、外层间隙,内、外圆半径4个结构参数对浮环轴承润滑特性和环速比的影响。结果表明,实际设计浮环时,需综合考虑结构参数对浮环润滑特性和环速比的影响及影响程度;浮环内层间隙增加,环速比降低,与内层间隙0.02 mm时相比,转速60 000 r/min时,内层间隙0.04 mm时的环速比减幅达23%,内层间隙增加,内、外膜温度减小,摩擦功耗略有增加,内层间隙0.03 mm时,浮环具有较理想的润滑性能和环速比;外层间隙0.06 mm的环速比均比外层间隙0.04 mm的环速比增加30%以上,外层间隙增加,外膜温度减小,且转速越高,外膜温度减幅越大;浮环内圆半径越小,环速比越小,内、外膜温度和摩擦功耗越小,浮环润滑性能越好;浮环外圆半径增加,环速比降低,但内膜温度、外膜温度、总摩擦功耗和总端泄流量变化幅度均在5%以内,外圆半径对浮环润滑性能影响不显著;浮环实际设计时,调整内圆半径比调整外圆半径对改善浮环润滑性能更有效。

Effect of structural parameters on lubrication performance of floating ring bearing and ring speed ratio in turbocharger

Turbochargers are widely used in internal combustion engines. The floating ring bearing is the most important part in the turbocharger, which is composed of inner film and outer film. The floating ring bearing can reduce the frictional power and oil film temperature. In the past, the lubrication performances of the floating ring bearing were analyzed without considering the heat transfer among the shaft, floating ring and bearing block. Furthermore, some researchers analyzed the lubrication performance of floating ring and the ring speed ratio separately. In reality, there exists heat transfer among the shaft, floating ring and bearing block and this part of heat will directly influence the lubrication performance of the floating ring. Besides, the change of the structural parameters may decrease ring speed ratio, which maybe is unfavorable to the practical operation if it is too small, and the change of the ring speed ratio may also influence the lubrication performance. So there exists a strong coupled relationship between the lubrication performance and ring speed ratio, and they can be studied more comprehensively and systematically with the change of structural parameters. The lubrication performance of floating ring bearing and the floating ring speed ratio in turbocharger were studied by considering the heat transfer among the shaft, floating ring and bearing block. Based on the Reynolds equation and the floating ring balance equation, the lubrication model of floating ring bearing was established. The Reynolds equation was solved by the finite difference method. The thermal deformation of the floating ring bearing was calculated by the thermal deformation equation. Comparative analysis on the influence of structural parameters on lubrication performance of floating ring bearing and floating ring speed ratio was performed, and the parameters included inner film clearance, outer film clearance, inner circle radius and outer circle radius. Results showed the effect and affecting level of structural parameter on lubrication performance and floating ring speed ratio should be considered comprehensively. The ring speed ratio decreased with the increase of inner film clearance. Compared with that inner film clearance is 0.02 mm, the ring speed ratio decreased 23% when inner film clearance is 0.04 mm. The inner film temperature, the outer film temperature decreased and the total friction power loss slightly increased with the increase of inner film clearance. The lubrication performance and ring speed ratio are ideal when inner film clearance is 0.03 mm. Compared with that outer film clearance is 0.04 mm,the ring speed ratio increased more than 30%. The outer film temperature decreased with the increase of outer film clearance. The higher the rotation speed, the greater the decrease amplitude of the outer film temperature. The smaller the inner circle radius, the smaller the floating ring speed ratio, and the smaller the inner film temperature, outer film temperature and total friction power loss. So the lubrication performance of the floating ring bearing will be improved with the decrease of the inner circle radius. The ring speed ratio decreased with the increase of the outer circle radius. But the inner film temperature, the outer film temperature increased, the total friction power loss and total oil leakage flowrate changed less than 5% with the increase of the outer circle radius. The outer circle radius has little effect on the lubrication performance of the floating ring bearing. Compared with the adjustment of the outer circle radius, it is more effective to improve the lubrication performance of floating ring bearing with the adjustment of the inner circle radius. There is a good agreement between the results predicted by the calculation model in this paper and some published experimental data.