叶片式混输泵非定常流动的数值模拟

为了加深对叶片式混输泵内相态分离和气体局部聚集现象形成机制的认识,在细泡状流动假设下,基于双流体模型对叶片式混输泵在进口含气率为15％条件下的气液两相输运过程进行非定常CFD模拟．计算中,湍流模型采用SST模型,相间作用力考虑了阻力和附加质量力,初始流场根据纯水工况的稳态计算解给定．对该含气率下的5个流量工况进行了计算,并以其中的最优工况为例分析了输运过程中两相流场的分布及其随时间的演变,探讨了非定常过程中扬程的计算方法及变化特点．结果表明:由于两相所受离心力不同,输运过程中气相主要分布于轮毂面附近;受流道形状变化和叶轮旋转的影响,叶轮进口区容易促发气团的形成,是气团形成的起始位置．输运过程中含气率场和压强场将出现波动,进而导致扬程值的大幅振荡,影响混输泵运行的稳定．通过对比扬程特性的计算和试验结果,说明了所用数值模型和方法的基本可靠性．

Numerical simulation of unsteady flow in multiphase rotodynamic pumps

To further investigate the mechanism of phase separation and gas accumulation in multiphase rotodynamic pumps, on the assumption of tiny bubbly flow, based on a two fluid model, the gas liquid two phase unsteady flow in a multiphase rotodynamic pump, with an IGVF（inlet gas vo lume fraction）of 15%, was numerically simulated. In the simulation, the k-ε based SST (Shear Stress Transport) model was used for turbulence; the drag force and the added mass force were taken into consideration in the interfacial momentum transfer terms; the steady solution of single water phase flow was specified as the initial flow field. Under this IGVF, five flow rate conditions were simulated, and taking the most optimal working condition as an example, the two phase flow field and its temporal evolution were analyzed; the evolution characteristic and the calculation method of pump head were explored. The results show that, due to different centrifugal forces on the two phases, the gas is distributed mainly around the hub; affected by the change of the flow passage and the rotation of the impeller, the air mass starts to form at the inlet of the impeller. In addition, the gas volume fraction field and pressure field fluctuate in transportation, which results in severe oscillation of the pump head and instability of the pump system. The comparison of the head characteristics between the simulation and the experiment validates the reliability of the numerical model and method.