轴承腔油气两相泡状流动的数值研究

Numerical Research on Two-Phase Gas/oil Bubble Flow in Bearing Chamber

航空发动机轴承腔过热或着火等现象与腔内油气两相泡状流动有关,需要通过数值计算研究两相泡状流动特性,从而为轴承腔润滑设计提供参考依据。针对上述问题,以某型航空发动机轴承腔为对象,建立轴承腔润滑油气液两相泡状流动模型,借助该模型研究润滑油介质运动状态。在建立模型方程时,考虑气泡直径尺寸大小和破裂聚合的影响,引入气泡种群方程和破裂聚合模型,并基于两流体模型和k-ε两方程湍流模型,建立轴承腔内润滑油两相泡状流动计算模型。通过数值计算,模拟出轴承腔内润滑介质流场,最后利用国外文献的试验数据对理论分析进行了验证。研究表明,轴承腔润滑介质中气泡直径尺寸分布状态以及与转速的关系,揭示空泡率、转子转速和润滑介质进口速度等工况条件对轴承腔润滑油性能的影响。与国外试验数据的对比证明了该理论分析方法在航空发动机轴承腔润滑系统设计的可靠性和可行性。

As regards to the relationship between overheat and fire and two phase gas/oil bubble flow in aero-engine bearing chamber, the characteristics of this flow are necessary to be studied by numerical calculation, which can provide reference to the design of lubrication of bearing chamber. For the one type of aero-engine bearing chamber, the bubble flow mathematical model is built and the flow characteristics can be further studied with this model. During building the model, N-S equations, coalescence and break-up factors are introduced for considering bubble diameters and breakup and coalescence effect. Based on two-body fluid model and k - ε turbulent model, the two-phase bubble flow in bearing chamber is established and solved by the finite difference method in three-dimension. As a result, the flow area is simulated. And the experimental data from foreign reference paper validate the theoretical analysis. The results show that the distribution of bubble in bearing chamber is relevant to shaft speed. It is also investigated how air/oil mixture speed and pressure at outlet is affected by physical parameters, such as void fraction, and condition parameters, such as rotor speed and air/oil mixture inlet speed. Finally, the proposed analysis is verified by the experimental data, which proves the theoretical method is feasible and reliable for the design of bearing chamber in aero-engine.