水轮机主轴中心孔补气对尾水管内部流态的影响

基于水气两相流模型，研究了水轮机主轴中心孔补气对尾水管涡带的影响以及对于改善水轮机内部流态的作用。研究表明，不同工况下最优补气量的大小有一定的差异；由于气体能量较小，补气量过小，在转轮的影响下它很快稀释于水体中，进入尾水管直锥段中心涡带区域的气体很少，起不到改善水流的作用，补气量过大，又会使断面过水面积减小，尾水管直锥段横向水流增强导致不利流态。研究成果揭示了补气量的大小对于改善尾水管内部水流的影响，从而为寻找最优的补气量提供理论依据。

Effect of air admission through center hole of turbine shaft on the flow in draft tube

The water_air two_phase flow model is applied to numerically study the effect of air admission through center hole of turbine shaft on the vortex band in draft tube and the flow regime. The results show that there are some differences of optimal air admission amount at different openings. When the amount of air admission is not enough, the energy of air is low. The air will be rapidly diluted into water, so that only a little of air can flow into the center of vortex and will not affect the flow regime. When the air amount is excessive, the area of flow cross section is reduced. It may enhance the cross_flow in conical tube.