液力偶合器气液界面追踪数值模拟

Numerical Simulation of Water-air Interface Tracking in Hydrodynamic Coupling

部分充液下液力偶合器内部介质运动为离心力场作用下的复杂两相流动,而液相分布形态对涡轮输出特性有着直接影响。为掌握偶合器内液相分布规律,将工作腔内介质运动视为分层流动,采用流体体积法(Volume of fluid,VOF)两相流模型,追踪562型标准桃形腔偶合器内不同工况下的气—液分界面。建立三维周期性流道模型,采用Realizable k-ε湍流模型和压力隐式算子分裂(Pressure-implicit with splitting of operators,PISO)压力耦合算法,并用内部面模拟泵、涡轮间的交互作用,转速比i=1.0和i=0.6时的叶片表面液相分布与文献中试验结果具有高度相似性。仿真结果表明,随泵涡轮间转差增大,气液分界面倾斜加剧,直至形成大的环流,而泵轮叶片压力面液相分布区域增大,吸力面液相减小;低挡圈(R=155 mm)对环流形态影响较小,主要起到限矩作用,而高挡圈(R=175 mm)可抑制大环流的产生。

The movement of fluid in a part-filled hydrodynamic coupling belongs to two-phase flow in centrifugal field,and the distributional pattern of liquid phase directly influences the output characteristic of turbine wheel.In order to acquaint the liquid distribution law,the movement of working medium is regarded as separated layer flow in a hydrodynamic coupling,and water-air interfaces of a standard peach shaped chamber coupling with effective diameter 562 mm in different working conditions are investigated by solving the volume of fluid（VOF） two-phase model.The periodic 3D flow channel model is built,the realizable k-ε turbulence model and PISO algorithm are employed in the numerical model,and the interior face is used to simulate the interaction between the pump wheel and turbine wheel.Water distribution on pump wheel blade is very similar to test result in the literature.The simulation results show that with the increasing of slip between pump wheel and turbine wheel,the incline of water-air interface becomes rapid and large circulation forms at last,and the distributing area of liquid on the pressure side of pump wheel blade increases while that on the suction side decreases.The results also show that low retainer has smaller influence on the circulation pattern than high one which seriously blocks the flow and stops the large circulation.