混流式水轮机叶道涡形成分析及抑制研究

Investigation on formations and alleviation of inter-blade vortices in Francis turbine

可再生能源的大力发展要求水电机组更加频繁地运行在部分负荷,以平衡电网参数,导致部分负荷下的叶道涡特性成为水轮机水力设计及优化的一个重要考核指标。本文基于理论分析和水轮机模型试验,分析了混流式水轮机叶道涡的形成原因,并提出抑制叶道涡初生和发展的有效措施。研究表明,水轮机转轮不能适应流量较大范围的变化而导致转轮内稳定连续的压力梯度被打破可能是影响叶道涡形成的因素之一。通过压缩转轮流道,采用仿生流线型设计及控制叶片扭曲程度对转轮进行改型,能够有效抑制和推迟叶道涡的初生及发展,为进一步扩大水轮机的稳定运行范围提供参考。

Hydropower units are forced to operate in part load conditions more frequently to balance the power grid parameters due to tremendous development of renewable energy resources;as a consequence,the characteristics of inter-blade vortices under such conditions become a significant index for evaluating hydraulic design and optimization of hydraulic turbines.This paper analyzes systematically the formation mechanism of inter-blade vortices in a Francis turbine through theoretical analysis and scale model experiment,and examines new effective measures for alleviating the incipient vortices and their development.Results show that breaking the pressure gradient that would otherwise be continuous and steady,due to the runner tending to adapt to the wide range of flow rate changes,could be one of the factors affecting the vortex formation.We find that design modification of the runner blades-shortening the runner flow passage,adopting a design of bionic streamline,or controlling the twist degree of the blades-can effectively suppress the incipient vortices and reduce their developing rate,achieving a useful result for expanding the stable operation range of Francis turbines.