卧式灯泡贯流式水轮机真机协联寻优数值研究

Numerical study of optimizing on-cam operation of horizontal bulb tubular turbines

众多实际电站的运行情况表明贯流式电站模型机与真机性能存在差异,使得很多电站投产后因协联关系不正确而频繁发生出力不足、剧烈振动等问题,但通过现场试验调整协联又耗时耗力。因此本文基于动网格技术,在考虑自由液面及水体重力的情况下对贯流式水轮机进行真机协联关系的数值寻优。结果表明:数值寻优前后低水头工况协联关系变化幅度更大,且低水头工况下效率对导叶开度变化敏感度更高,因此电站在丰水期低水头工况下更有必要对协联关系进行调整,数值模拟协联寻优对低水头工况指导意义更大;协联关系的变化对转轮靠轮毂处的水流流动影响较大,相对液流角增加,同时转轮出口靠轮毂处的正环量减小,很好地改善了尾水管内的回流及涡带分布状态,有助于减小尾水管内的水力损失,提高水轮机的水力效率。所以数值协联寻优对贯流机组的设计和现场试验具有一定的指导意义。

Differences exist between the prototype machine at a tubular power station and its model machine,often leading to an incorrect on-cam operation relationship of the guide vanes and runner blades.This could cause many power stations after being put into operation to suffer from insufficient output and severe vibration.However,adjusting the on-cam operation through on-site prototype experiments is time-consuming and labor-intensive.In this work,numerical optimization of the on-cam operation of a prototype tubular turbine is studied using the dynamic grid technology,considering the effect of free surface and water gravity.The results show that before and after the optimization in low head conditions,the turbine has a wider range of variations in on-cam operation,and its efficiency is more sensitive to changes in guide vane opening.Therefore,for a hydropower station under low head conditions during the wet season,an on-cam operation adjustment is more necessary,and numerical simulations of the optimization is of greater significance.An adjustment to on-cam operation usually imposes a significant impact on the flow regime in the runner near the hub,and a good one will cause an increase in the relative flow angle and a decrease in the positive circular rector at the outlet of the runner near the hub.This brings about a significant improvement in the distribution of backflows and vortex belts in the draft tube,thereby reducing hydraulic loss in the draft tube and raising hydraulic efficiency of the tubular turbine.Thus,numerical optimization of on-cam operation is a useful guide for the design and field test of tubular units.