叶轮叶片数对液力透平性能的影响

The Effect of Impeller Blade Number on the Performance of Pumps as Turbines

叶轮叶片数是液力透平的主要设计参数之一,为了研究叶片数对液力透平的影响,采用流场模拟软件ANSYS CFX对叶片数Z=5、7、9的液力透平进行数值模拟,得出不同叶片数下液力透平的扬程和效率曲线、导叶和叶轮的内部压力场及速度流线场分布。对性能曲线分析得出:叶片数对液力透平的扬程影响不大;效率曲线存在零效率点,零效率点流量Q7>Q5>Q9;在大流量工况下,效率曲线下降平缓且η7>η5>η9;对内部流场研究可知:随着叶片数增加,液体受挤压越严重,压力梯度越明显,叶轮进口的漩涡区域逐渐减少,内部流动得到有效的改善。当Q>180m3/h时,叶轮效率曲线和叶轮水力损失曲线变化平缓,且叶片数7的叶轮效率最高,水力损失最少。综上所述:液力透平适合在大流量区域运行且最优叶片数为7。

The number of impeller blades is one of the main design parameters of the pump. , In order to study the impact of blade number on the pump as the turbine, computational fluid dynamics software ANSYS CFX is adopted in the flow field analysis under the conditions that the blade number Z=5,7 and 9, then the different head and the efficiency curves of the pump as turbine is ob- tained as well as the internal pressure field and velocity streamline of the impeller and guide vane. An Analysis of the performance curve shows that： the number of blades has little effect on the head of the pump as turbine. There is zero efficiency point on the effi- ciency curve and the flow rate of zero efficiency point is QT）Qs ）Q9 under high flow conditions. An Analysis of the internal flow field shows that： with the increase in the number of blades, the fluid is squeezed more seriously and the pressure gradient becomes more obvious, and the impeller inlet area of the vortex region is gradually decreased and the internal flow is improved effectively. When Q）180 ma/h, the impeller efficiency curve and the impeller hydraulic loss curve changes gently, the efficiency is the highest and the hydraulic loss is the least when Z= 7. A conclusion is drawn that the pump as turbine is suitable to be run under the large flow conditions and the optimum number of blades is 7.