引水部件水力损失对水轮机增容后效率的影响

Study on hydraulic loss upstream the runner and its effects on efficiency of refurbished turbine

水电站增容改造市场具有广阔的前景。但老电站的技术改造受到埋设部件不变及同步转速不变的限制,往往要通过提高过流量达到增容目的。在流道不变的条件下,流量的增加必然引起过流部件水力损失增加,可能导致效率下降。本文分析了引水部件水力损失对水轮机功率和效率的影响,提出了在法向出流条件下水轮机流量和功率的估算公式,据此提出了按增容功率要求估算水轮机流量、导叶安放角及效率的方法。以一个具体电站为例,通过流场数值模拟,分析了引水部件内水力损失与流量的关系,进而对水轮机增容后效率的影响进行了分析。建议电站根据自身的实际条件科学地提出机组改造的技术指标,同时建议在条件允许时可将标准导叶改为负曲率导叶,可在较小的流量下获得必要的导叶出口环量,提高水轮机的整机效率。

The rehabilitation projects have a huge market in China.In these projects,the flow rates of the turbines are always increased to increase the output.Since the buried parts and the rotational speed keep unchanged,the increase of flow rate will raise hydraulic loss in the whole flow path,thus may decrease the efficiency.In this paper,the hydraulic losses in spiral casing,stay vanes and guide vanes and their effects on the output and efficiency are analyzed.A method is proposed to evaluate the flow rate and guide vane opening for the refurbished turbines.As an example,the hydraulic losses in buried parts of a real case are calculated through flow simulations and the efficiency of the refurbished turbine is evaluated based on these results.Modification of the guide vane profile is suggested for higher efficiency with less flow rate increase.