高比转数蜗壳式混流泵准三元水力设计与数值计算

Quasi 3-D design and numerical simulation of high specific speed volute mixed-flow pump

针对高比转数蜗壳式混流泵水力设计研究偏少的现状,在准三元设计理论的基础上,采用不考虑黏性的三元反问题设计与考虑黏性的三元正问题数值计算相结合的方法,设计得到了比转数为603的蜗壳式混流泵,以深入探索三元水力设计方法在开发高比转数蜗壳式混流泵的适用性.在三元反问题设计过程中,首先采用二元水力设计方法得到初始的混流泵模型,然后给定"S"型速度矩沿轴面流线的分布规律,完成新的蜗壳式混流泵的水力设计.应用计算流体力学软件CFX,采用标准k-ε湍流模型,SIMPLE算法求解三维稳态不可压缩雷诺时均N-S方程,分别在设计工况、小流量和大流量工况下对新型泵进行了数值模拟,并且分析对比了泵的水力性能.数值模拟计算结果表明,新型泵叶轮和蜗壳内部流线整齐有规律,叶片工作面和背面静压力分布均匀合理,叶轮叶片轮缘和轮毂附近速度矩沿轴面流线自进口边到出口边的分布规律基本符合"S"型,并且在设计工况下的效率比采用速度系数方法设计的原型泵有了提高,满足了对高比转数蜗壳式混流泵水力性能的要求.

In the light of little research work on high specific speed volute mixed-flow pumps,the design method of combining non-viscous three-dimensional inverse design method with viscous three-dimensional direct problem to a volute mixed-flow pump with specific speed 603 was applied.Based on quasi three-dimensional pump design theory,the validity of three-dimensional hydraulic design method in developing the high specific speed volute mixed-flow pumps was investigated.During the three-dimensional inverse design,first a mixed-flow pump as the initial computational model was obtained by using two-dimensional hydraulic design technique,then the S-shaped velocity moment distribution along meridional streamlines was specified,finally a new volute mixed-flow pump was generated.Tosolve three-dimensional steady Reynolds averaged N-S equations,CFD software CFX,standard k-εturbulence model and SIMPLE algorithm were used.The computations of the newly designed pump under three operating conditions including design condition,low flow rate and large flow rate conditions were performed to analyze its hydraulic performance.The numerical simulation results show that the newly designed pump has regular streamlines in impeller and volute flow passages,and the static pressure distribution in pressure side and suction side of the impeller is even and reasonable.The velocity moment distribution in the vicinity of impeller tip and hub from leading edge to trailing edge is nearly the same as S shape.Under the design operating condition the newly designed pump＇s efficiency is higher than the initial pump＇s,which is designed with the method of flow velocity coefficients.The newly designed pump has fulfilled the requirement of hydraulic performance for high specific speed volute mixed-flow pump.