导叶开度对贯流式水轮机性能及流动特征的影响

Influence of guide vane opening on performance and flow characteristics of tubular hydro-turbine

针对某型号贯流式水轮机,运用ANSYS CFX,分别在导叶开度为1 550,1 405和1 278 mm条件下,对水轮机内部三维流场进行全流道数值模拟,研究导叶开度对水轮机性能及流动特征的影响.通过分析对比3种开度下水轮机水头和效率,同时研究全流道截面压力、速度分布,导叶外环面压力分布,导叶叶片压力分布以及转轮叶片压力分布,得出开度为1 405 mm是与转轮匹配性最佳的导叶开度.进而对最佳导叶开度下水轮机在0.8Q,1.0Q,1.2Q这3种工况下的空化进行模拟,结果发现空化很大程度地降低了水轮机的水头和效率.同时对转轮、转轮叶片以及尾水管的空泡相体积分数的分布进行了分析,得知在设计工况下的空化程度最轻,小流量工况下的转轮内空化比较严重,而在大流量工况下,空化区从转轮出口延伸到尾水管内.

In order to investigate into the effects of guide vane opening on the performance and internal flow characteristics of a tubular hydro-turbine,a series of numerical simulations are performed using ANSYS CFX at three openings such as 1 550,1 405 and 1 278 mm. Considering the turbine operation head and efficiency,the pressure and velocity distributions in the cross-sections of flow channel,the pressure profiles on the gate vanes and runner blades are analyzed. It is found that 1 405 mm is the optimal opening at which the guide vane matches the runner in hydrodynamics exactly. Moreover the cavitating flow in the hydro-turbine is simulated at the best guide vane opening under three operating conditions,namely 0. 8Q,1. 0Q and 1. 2Q. It is identified that the head and efficiency are reduced significantly due to cavitation. The vapor volume fraction distributions in the runner and draft tube are observed. It is shown that cavitation severity is the least at 1. 0Q of the design flow rate. At 0. 8Q,thecavitation in the runner is the most serious; while at 1. 2Q,the cavitation zone extends to the draft tube from the runner.