Abstract: In order to study the internal flow characteristics of a multistage hydraulic turbine under transient conditions, a two-stage centrifugal pump reversing hydraulic turbine is taken as the research object, and large eddy simulation turbulence model considering the dynamic sublattice stress mode of nonlinear velocity gradient and helix is constructed, considering the nonlinear velocity gradient and helicity, construct the dynamic subgrid stress mode of large vortex turbulence model, the simulation of the variation of the instantaneous pressure pulse, and analyze the transient condition. The results show that under transient conditions, flow transients can cause sudden changes in pressure pulsation of various components inside the hydraulic turbine, and the sudden pressure intensity far exceeds the amplitude of the pressure pulsation of the components inside the hydraulic turbine itself, in which the inlet chamber is most affected by the flow transient, and the impeller is relatively less affected by the flow transient. When the hydraulic turbine is under transient conditions, the velocity streamline distribution of the inlet chamber is more uniform, and the velocity streamline distribution at the impeller becomes relatively uniform, but the velocity streamline distribution at the interstage guide vanes and the outlet chamber is relatively chaotic where are more vortices. The research results will provide a theoretical basis for the improvement of hydraulic turbine structure in the fields of hydrogen energy storage of new energy vehicles and petrochemical industry.

Key words: Multistage hydraulic turbine; Transient conditions; Internal flow characteristics; Numerical simulation

摘要： 为了研究多级液力透平瞬变工况时的内部流动特性，以一个二级离心泵反转式液力透 平为研究对象，考虑非线性速度梯度与螺旋度影响，构建动态亚格子应力模式的大涡模拟湍 流模型，对多级液力透平内部流场进行全流域非定常数值模拟，获得瞬变工况下液力透平内 部流场的瞬时压力脉动的变化规律，并分析瞬变工况下涡流在液力透平内部的演变规律。结 果表明，瞬变工况下，流量瞬变会引起液力透平内部各部件的压力脉动突变，该突变压力强 度远超过液力透平内部各部件自身的压力脉动幅度，其中进水室受流量瞬变的影响最大，叶 轮受流量瞬变的影响相对比较小。液力透平在瞬变工况时，进水室的速度流线分布更加均匀， 叶轮处的速度流线分布也变得相对均匀，但级间导叶处和出水室的速度流线分布更加杂乱， 旋涡比较多。研究结果将为新能源车辆氢能储能、石油化工等领域中的液力透平结构改进提 供理论依据。

关键词: 多级液力透平；瞬变工况；内部流动特性；数值模拟