基于涡分析的贯流式水轮机尾水管流动分析

Flow analysis of tubular turbine draft tube based on vortex analysis

为了研究贯流式水轮机尾水管的内部流动情况,基于正则化螺旋度方法和流线分析涡和涡带,对贯流式水轮机小流量、额定流量和大流量进行非定常计算,对比分析了3个工况下尾水管内部的流动特征。研究表明:小流量工况下,水轮机尾水管内存在一个与转轮旋转方向一致的螺旋状涡带,大流量工况下,水轮机内存在一个与转轮旋转方向相反的螺旋状涡带,且2种工况涡带都按一定周期演变。在小流量工况下,涡带周期运动持续到尾水管的中后位置,在大流量工况下,涡带周期运动在尾水管的前中部位置。根据正则化螺旋度方法分析得出在小流量工况下,涡带导致尾水管壁面两侧出现的涡旋旋转方向相反;比较正则化螺旋度方法和流线分析得出,正则化螺旋度方法分析涡旋的位置和范围比流线分析更加准确;2种偏工况下的涡带形态和发展类似,但大流量工况对应的阈值更大,表明该工况对应的尾水管流态更紊乱。

In order to study the internal flow of draft tube of tubular turbine,the unsteady numerical simulation of the small flow,rated flow and large flow of the tubular turbine is carried out based on the regularized helicity method and the streamline analysis vortex and vortex rope,and the flow characteristics of the draft tube under three working conditions are compared and analyzed.The research shows that under small flow condition,there is a spiral vortex rope in the turbine draft tube that is in the same direction of rotation with the runner;under large flow conditions,there is a spiral vortex rope in the turbine in the opposite direction of rotation of the runner.The vortex ropes of both conditions evolve in a certain period.Under low flow conditions,the vortex rope periodic motion continues to the mid-rear position of the draft tube.While under large flow conditions,the vortex rope moves in the front-middle position of the draft tube.According to the regularized helicity method,the vortex rope causes the vortex rotation directions to be opposite on both sides of the draft tube wall in the low flow condition.Comparing the results of regularized helicity method and the streamline analysis,it is indicated that the position and region of the vortex of the regularized helicity method are more accurate than those of streamline analysis.The vortex morphology and development under the two off-working conditions are similar,but the threshold corresponding to the large flow condition is larger,which indicates that the flow in draft tube in the large flow condition is more disordered.