轴承腔中均匀流体/壁面油膜分层流动分析

Analysis of Homogeneous Fluid/wall Oil Film Two-phase Stratified Flow in an Aeroengine Bearing Chamber

航空发动机轴承腔精确的润滑与换热设计依赖于对其内油气两相润滑介质流动与换热本质的认识。针对轴承腔内复杂的油气两相润滑介质流动状态,建立轴承腔均匀流体/壁面油膜分层流动分析模型,开展腔内油气两相润滑介质流动特性研究,探讨转子转速和润滑油供油量对均匀流体和壁面油膜两相介质压力、速度以及温度分布的影响。分析模型中,气相介质(含油滴)的等效物理特征参数通过离散油滴和气相介质的组分比例关系确定,各固体壁面与流体介质的对流换热系数根据其各自的传热特性确定。研究结果表明,均匀流体与壁面油膜两相介质的压力随着润滑油供油量的增加而增大,受转子转速的影响较为复杂;均匀流体与壁面油膜两相介质的速度随着转子转速的增高而增大,受润滑油供油量影响较小;均匀流体的温度随着润滑油供油量的增加而减小,受转子转速的影响较小;与均匀流体温度不同,壁面油膜的温度随着转子转速的增加而增大,随着润滑油供油量的增加而减小。建立了轴承腔试验台系统,开展了轴承腔油气两相流动状态下的压力和温度测试,压力和温度试验结果与理论计算结果均具有较好的吻合性,验证了提出的理论分析方法的可靠性。

The accurate lubrication and heat transfer designs of an aeroengine bearing chamber require an understanding of the complex air/oil two-phase flow characteristics in the chamber. A homogeneous fluid/wall oil film two-phase stratified flow model is proposed to investigate the air/oil two-phase lubrication medium flow in an aeroengine bearing chamber, and the effects of shaft speed and oil mass flow rate on the pressure, flow velocity and temperature for the homogeneous fluid and wall oil film are discussed in detail. In the model, the equivalent physical feature parameters of air （containing droplets） are determined by the component rate of droplets and air in the mixture of air and droplets, and the convection heat transfer coefficients between relevant walls and fluid medium in the bearing chamber are calculated by their convection heat transfer characteristics, respectively. The calculation results show preliminarily that the pressures of the homogenous fluid and wall oil film increase with increasing oil mass flow rate, and are influenced complexly by shaft speed;that the flow velocities of the homogenous fluid and wall oil film increase with increasing shaft speed, and are influenced insignificantly by oil mass flow rate;that the homogenous fluid temperature decreases with increasing oil mass flow rate, and are influenced slightly by shaft speed;and that the wall oil film temperature increases with increasing shaft speed and decreasing oil mass flow rate. Finally, a bearing chamber experimental facility is built, and the pressure and temperature under the air/oil two-phase flow condition are measured in the bearing chamber. The calculation results agree well with experimental data.