襟翼长度对混流式水轮机空化性能的影响

Effect of Flap Length on Cavitation Performance of Francis Turbine

为了研究襟翼结构尺寸对水轮机空化性能的影响,以HLX180-LJ-145混流式水轮机为原型,应用UG建立在原型转轮进口靠近下环处两叶片中间位置增加襟翼结构的加襟翼转轮模型为研究对象,利用ANSYS CFX软件对0.8Q_(d)小流量和1.0Q_(d)设计流量工况点清水和含沙水介质下的转轮空化现象进行数值分析,分别采用长度在60 mm、80 mm和100 mm的3种襟翼,对比两种流量工况下加入襟翼前后混流式水轮机转轮内部流动形态,研究襟翼长度对水轮机空化性能的影响。结果表明:转轮叶片吸力面靠近转轮出口处易产生空化,增加襟翼后,转轮内总受压面积增大,空泡体积分数减小,转轮进口来流得到充分分流,带襟翼转轮过流通道的叶栅稠密度增加,叶片表面流动分离延迟,水流流线变得顺畅,水流流态变好,含沙水对转轮的磨蚀冲击减弱,空化性能得到明显的改善。该研究对不同水流介质下的水轮机改造设计与优化具有一定的参考作用。

Cavitation abrasion seriously affectes the safe and stable operation of the Francis turbine unit.HLX180-LJ-145 Francis turbine was selected as the researchobject.Based on the original runner,a flap structure is added in the middle of the two blades,which is fixed at the runner inlet near the lower ring.ANSYS CFX software is used to conduct numerical analysis on the runner cavitation phenomenon under clean water and sandy water at the operating point of 0.8Q_(d) small flow and 1.0Q_(d) design flow Three kinds of flaps of 80 mm and 100 mm are used to compare the internal flow patterns of Francis turbine runner before and after adding flaps under two flow conditions,and analyze the influence of flap length on cavitation performance of hydraulic turbine.The results show that the suction surface of the runner blade close to the runner outlet is prone to cavitation.The total pressure area in the runner is increased with the increase of flaps,the volume fraction of cavitation decreases,the flow from the runner inlet is fully divided,the cascade density of the runner passage with flaps increases,the flow separation on the blade surface is delayed,the flow streamline becomes smooth,the flow pattern becomes better,and the abrasion impact of sand water on the runner is weakened,The cavitation performance is obviously improved.