机组导叶关闭规律对相继甩工况的影响

Influence of closure law of wicket gate on successive load rejection condition

针对"一洞两机"布置型式的抽水蓄能电站,基于瞬变流理论和特征线法,采用多种关闭规律对实际工程进行数值模拟;分析不同关闭规律对相继甩负荷工况时尾水进口最小压力产生影响的内在机理,得到针对尾水进口最小压力的最优关闭规律求解方法.结果表明不同关闭规律可决定尾水进口最小压力出现在先甩机组还是后甩机组工况.采取适当的先慢后快关闭规律可以使得2台机组在各自最不利时刻点的尾水进口最小压力近似相等,并优于其他关闭规律.求解该关闭规律步骤:初步选择一种两段折线关闭规律,若后甩机组尾水进口最小压力小于先甩机组的,则应将关闭规律做调整:将第1段折线斜率改小,将第2段折线斜率改大;若后甩机组尾水进口最小压力大于先甩机组的,则反之,直至2台机组尾水进口最小压力近似相等为止.

Focusing on pumped-storage power stations with layout of two units per penstock,a few closure laws of wicket gate were applied in transient flow numerical simulations in a practical pumpedstorage power station based on transient flow theory and method of characteristics. The mechanism of closure law influencing the minimum pressure at the draft tube inlet was analyzed when a successive load rejection happened to find out the best closure law for the minimum pressure. The results show that a given closure law can decide the minimum pressure at the draft tube inlet to happen in the unit with first load rejection or the unit with late load rejection. Adopting a firstly slow then fast closing closure law can allow two units to have a nearly equal minimum pressure at the draft tube inlet at most unfavorable moments,respectively,showing a better law than the others. The procedure for obtaining such a closure law is as follows. Firstly,a closure law with two-piece line is selected. If the minimum pressureat the draft tube inlet in the unit with late load rejection is lower than in the unit with first load rejection,the law should be adjusted in such a way that the first piece line slope is increased and the second one is reduced. If not,the closure law should be adjusted vice versa until two units sharing approximately the same minimum pressure at the draft tube inlet.