轴流泵装置模型断电飞逸过程三维湍流数值模拟

Numerical simulation of transient flow in axial-flow pump unit model during runaway caused from power failure

针对轴流泵装置模型断电飞逸过程特点,对应叶轮区所采用的冻结叶轮的变速旋转坐标系方法与基于任意拉格朗日-欧拉方法(ALE)的变速滑移网格法,构建基于三维非定常RANS方程与Spalart-Allmaras湍流模型的数值模拟方法,采用有限体积法对控制方程组进行离散,时间项采用一阶向后差分隐式格式,方程组中扩散项采用二阶中心差分格式,对流项采用二阶迎风格式,应用SIMPLEC方法进行速度压力耦合求解,采用初始工况的定常计算结果作为非定常计算的初始流场.经过轴流泵装置模型断电飞逸过程的数值模拟,获得了机组到达最大转速时所需时间为20.35 s,以及两种数值方法所得最大飞逸转速分别为1 610,1 989 r/min,装置模型稳态飞逸试验转速1 720 r/min,介于两者之间,同时揭示了机组转速、流量、转矩与测点压力等参数随时间变化规律与装置模型流道子午截面流速场、叶轮叶片压力场的瞬变过程,从而为机组结构优化设计和运行管理提供科学的参考依据.

A three-dimensional unsteady CFD simulation method was established based on the RANS equations and Spalart - Allmaras turbulence model by varying rotating speed of reference fiame and sliding mesh techniques to simulate the transient flow in an axial pmnp unit model in the runaway caused from power failure. The governing equations of fluid flow are discretized with the finite volmne method; the temporal item is approximated with a first-order backward difference implicit scheme, a second-order central difference scheme is applied to the source and diffusion items, a second-order up- wind scheme is for the convection items, and the velocity-pressure coupling method is chosen to be SIMPLEC. A steady simulation was performed first for providing an initial condition to the transient case. The results showed that the pump attained its runway speed in 20.35 s. The estimated runway speeds were 1 610 r/rain and 1 989 r/rain by two techniques, comparing with the experimental speed of 1 720 r/rain. Additionally, the pump rotational speed, flow rate, torque and static pressure at moni- tor points against time were revealed during the transient period. These data will provide a reference for pump design and operation of pumping station.