转轴空腔对增压器涡轮轴应力及传热影响的研究

Effect of Shaft Cavity on Stress and Heat Transfer of Turbocharger Turbine Shaft

热负荷的提升对涡轮增压器涡轮端及轴系零部件的可靠性带来了严峻挑战,转轴高温变色及机油结焦已经成为涡轮增压器主要故障模式之一。涡轮转轴空腔可以阻挡热量从涡轮头向转轴的传递,利用数值仿真方法研究了不同空腔直径及浮动轴承位置传热系数对涡轮应力及传热特性的影响,结果表明:转轴空腔使得涡轮背盘R圆角应力降低,但是增加了其自身发生低周疲劳失效的风险;空腔直径越大,热阻效果越明显,相比较于无空腔方案,转轴空腔使涡轮头向涡端浮动轴承的热量传递减小0.8%~4.4%,使涡端浮动轴承对应转轴的最高温度降低2.3~9.9℃。

The increase of thermal load has brought severe challenges to the reliability of turbocharger turbine end and shaft-attached components and the high-temperature discoloration of rotating shaft and the coking of lubricating oil have become the main failure modes of turbocharger.The cavity of turbine shaft can block the heat transfer from turbine head to shaft.Numerical simulation methods were used to study the effects of different cavity diameters and shaft heat transfer coefficients at the position of floating bearing on stress and heat transfer characteristics of turbine.The results show that the shaft cavity decreases the stress of R fillet for turbine back disk,but increases the risk of low cycle fatigue failure.The larger cavity diameter will lead to the more obvious thermal resistance effect.Compared with the case without cavity,the heat transfer from turbine head to floating bearing at the turbine end reduces by 0.8%-4.4%,and the shaft maximum temperature adjacent to floating bearing at the turbine end decreases by 2.3-9.9℃.