变顶高尾水系统尾水管进口真空度的近似公式  

Approximate formula for vacuum degree at the inlet of a draft tube in a tailrace with inclined ceiling

作　　者：缪明非[1] 张永良[1] 

机构地区：[1]清华大学水利水电工程系,水沙科学与水利水电工程国家重点实验室,北京100084

出　　处：《水力发电学报》2011年第2期49-53,共5页Journal of Hydroelectric Engineering

基　　金：国家自然科学基金(50539070);973项目(2006CB403304)

摘　　要：本文研究了甩负荷工况下变顶高尾水管进口真空度的近似计算公式。在水击波相数较大情况下,可忽略水体和尾水洞壁弹性。本文从非恒定渐变流动的Bernoulli方程出发,推导出变顶高尾水系统在甩负荷情况下尾水管进口处真空度计算的基本方程。讨论了基本方程中的静力真空项、动力真空项和惯性真空项,得出并简化了最大真空度计算公式。该近似公式计算结果与物理模型试验结果接近。在水轮机导叶缓慢关闭和尾水洞较短的情况下,近似公式可应用于工程初步设计。In this paper the approximate formula was studied for vacuum degree at the inlet of a draft tube in a tailrace with inclined ceiling.In the condition of adequate water hammer phase number,the elasticity of water and tunnel wall is negligible.By applying the Bernoulli equation of one dimension unsteady flow,a basic equation for the vacuum degree at the inlet of a draft tube in a tailrace with inclined ceiling was derived.Through a simplification of the equation by considering the terms of static vacuum,kinetic vacuum and inertia vacuum,an approximate formula for calculating the maximal vacuum degree at the draft tube inlet in the course of guide vanes closing was obtained.Experimental verification showed that this formula produces a good accuracy.The formula is applicable to the situation of slow guide vanes closing and a short tailrace.

关 键 词：水力学 变顶高尾水洞 尾水管 水力过渡 真空度 

分 类 号：TQ028.8[化学工程]