S形贯流泵装置水力模型非定常水动力特性分析

Unsteady Hydrodynamic Performance of Hydraulic Model in S-shaped Shaft Extension Tubular Pumping System

水力模型的非定常水动力特性对泵装置的安全运行稳定性具有重要影响,在考虑了水力模型与流道的水力相互作用基础上,采用雷诺时均Navier-Stokes控制方程和RNG k-ε湍流模型对多工况时S形贯流泵装置进行了全流道非定常数值模拟,分析了水力模型的非定常水动力特性.泵装置非定常数值预测结果与试验值进行对比,验证了数值模型的可信性.计算结果表明:随叶轮的旋转,叶轮轴向力的变幅小于径向力的变幅,在小流量工况时径向力变幅最大.不同工况时叶轮的非定常脉动轴向力受转频的影响程度大于非定常脉动径向力,轴向力和径向力的脉动主频均以低频为主.在叶轮的1个旋转物理周期内叶轮的径向力分量呈蝶形分布.随流量的增大,径向力的平均值也增大,绕Z轴方向的扭矩则逐渐减小.相比大流量和小流量工况时,叶轮叶片的脉动比值在高效工况时最小,表明偏离高效工况运行时,叶轮受周期性水动荷载的影响较大,应尽量避免泵装置在偏离高效工况区域运行.随流量的增大,导叶片的脉动比值也增大.

The unsteady hydrodynamic characteristics of hydraulic model have an important influence on the operation stability of S-shaped shaft extension tubular pumping system. In order to precisely analyze the unsteady hydrodynamic characteristics of hydraulic model,the threedimensional unsteady turbulent flow field of pumping system was simulated based on the RNG k-ε turbulent model and Reynolds time-averaged equation. Comparison of numerical simulation results and experimental values under different operation conditions verifies the accuracy of the numerical model. The results show that,with the rotation of impeller,the amplitude of axial force is lower than that of radial force for impeller,and the amplitude of radial force in small flowrate conditions is large than other operating conditions. Unsteady axial force of impeller is affected by rotation frequency than unsteady radial force in different operating conditions,and the dominant frequency of axial and radial force is low frequency fluctuation. The distribution of radial force components is butterfly in a rotation period. With the increase of flowrate,the average of radial force increases gradually,while the Z-axis torque decreases gradually. The fluctuation ratio of blade in high efficiency operating condition is larger than other operating conditions,which show that period hydrodynamic loads have an great influence on impeller in off-high efficiency operating condition. The fluctuation ratio of guide vane blade increases with the increase of flowrate.