向心透平级叶轮内三维复杂流动的数值研究

Numerical Investigation on Three-Dimensional Complexity Flows in a Wheel of Radial Inflow Turbine

对向心透平叶轮内部复杂流动在级环境下进行了全三维黏性数值模拟,结合拓扑学原理分析了设计工况和非设计工况下其内流动分离及各种涡系发展的演变过程,初步建立了向心透平叶轮内的旋涡模型,阐述了流动损失的形成机理。研究表明:向心透平叶轮内部涡系与轴流式透平存在较大差别,且流动分离及涡系主要集中在吸力面侧;设计工况下向心透平叶轮内的主要旋涡包括马蹄涡、通道涡及泄漏涡,其主要表现为通道涡与泄漏涡相互影响和掺混,是主要损失的形成原因;非设计工况下,主流在叶轮叶片前缘处发生大范围的分离及回流,造成了较大的能量损失,但二次流损失所占比例较小。

The 3D complex internal flows in a wheel of radial inflow turbine was investigated under the stage environment. Based on topology theory, the rules of flow separation and vortex development in the wheel were analyzed both at design and off design conditions. The vortex model for the wheel is preliminarily established, and the loss mechanism is discussed. The results show that the vortex structures in a radial inflow turbine wheel are greatly different from those in an axial turbine. Flow separation and vortex system mainly concentrate on the suction side of the wheel. At design condition the primary vortex structures in a radial inflow turbine wheel include the horseshoe vortex, the passage vortex and the tip leakage vortex, and the vortex structures are mainly presented as the interaction and mixing between passage vortex and tip leakage vortex, which is the major reason of flow loss formation. At off design conditions, the flow separation and backflow of mean flow occur at the leading edge which causes the majority of energy loss, and the secondary flow loss account for a relatively small part in the wheel.