尾水调压室位置对尾水管最小压力值的影响

尾水调压室位置是影响尾水管最小压力值的主要因素之一。本文通过理论分析、数值计算和工程实例,证明尾水调压室越过其临界位置向厂房方向移动,尾水管最小压力值变化不大、并略有恶化。该结果有利于地下厂房和尾水调压室的布置,缓解了洞室围岩稳定和过渡过程之间的矛盾。究其物理本质,在机组特性、导叶关闭规律确定的前提下,尾水管最小压力主要取决于尾水管延长段的水击压力、阻抗损失和调压室涌浪水位三者的叠加。由于尾水道总长度不变,移动尾水调压室位置,三者所起的作用相互消长,所以必然存在着有利于尾水管最小压力值的调压室临界位置。

Effect of tailrace surge tank location on minimum pressure in draft tube

The location of the tailrace surge tank is one of the main factors effecting minimum pressure in the draft tube.By theoretical analysis,numerical calculation and engineering example,it is proved that little worse minute fluctuation of the minimum pressure in draft tube happens when the tailrace surge tank is moved towards the plant house exceeding the critical position.This conclusion has special reference to the arrangements of the underground hydropower plants and the tailrace surge tank.It also moderates the contradictory between the stability of surround rocks and the safety in transient process.Investigating its physical essence,under the premise that the characteristic of hydraulic turbines and the law of guide vane closing are confirmed,the minimum pressure in draft tube is mainly decided by the superposition of the water hammer pressure in extension part of the draft tube,impedance loss and the water level in the tailrace surge tank.When the length of the tailrace conduit is unvaried,the tailrace surge tank is shifted in a certain scope,the effects of those factors are interacted.Hence,there must be a critical location of the tailrace surge tank with great advantage to the minimum pressure in draft tube.