叶片高压边安放角对高水头水泵水轮机性能的影响

基于低比转数混流式转轮设计程序,在保证转轮其他参数一致的条件下,分别设计了3个具有不同高压边安放角的叶片,并采用CFD技术对3个转轮分别进行了5个水轮机工况和5个水泵工况的全流道数值模拟,分析了叶片高压边安放角对水泵水轮机能量特性、水轮机工况转轮的来流和水泵工况转轮与活动导叶的动静干涉现象的影响.研究表明,水轮机工况下,数值计算的叶片冲角绝对值大于给定冲角的绝对值,叶片的负冲角越大,导致转轮进口撞击越剧烈,引起水轮机工况水力效率略有下降,但是对转轮内流态扰动很小.水泵工况下,叶片高压边安放角越大,与其相匹配的活动导叶转角越小;由于安放角2叶片与14°转角的活动导叶和固定导叶三者相匹配,其水力效率相对最高;而其他3种高压边安放角叶片由于不匹配,内部流场出现了撞击、脱流和回流等不稳定现象,引起水泵工况水力效率的严重下降.

Effects of blade angle at high pressure end on performance of pump-turbine with high head

Based on a design procedure for low specific speed Francis runners, three kinds of blades with different blade angles at high pressure end are generated while the rest parameter remain unchanged. The steady, three-dimensional turbulent flows in the pump-turbines with those blades are simulated by means of CFD method at five flow rates to identify the effects of the blade angle on the performance in pump and turbine modes and the inflow condition in the turbine mode as well as the rotor-stator interaction in the pump mode. It is proven that the predicted angle of attack is different from the angle prescribed in the design and the runner is subject to a negative angle of attack in the turbine mode, which results in a remarked shock loss and a slight efficiency reduction but the flow in the runner seems little affected. In the pump mode, the larger the blade angle is, the smaller the rotational angle of the guide vanes is. The hydraulic efficiency is the highest in that mode with blade angle 2, which matches the 14? rotational angle of the guide vane and the stay vane. However, the other two kinds of blade angles mismatch the guide vane and the stay vane, causing instable phenomena, such as shock, reverse flow and flow separation and so on, and leading to a serious declination in the hydraulic efficiency.