贯流泵装置出水流道进口区压力及速度场分析

为分析贯流泵装置出水流道进口区流场的非定常特性,在考虑水泵与流道的水力相互作用基础上,采用RNG k-ε湍流模型对贯流泵装置进行全流道的非定常数值计算。通过非定常求解预测的贯流泵装置能量性能数据与物理模型试验值进行对比,验证数值计算方法的可信度,分析出水流道进口区非定常压力及速度场的演变规律。结果表明:(a)贯流泵装置数值预测的扬程系数与模型试验结果的最大相对误差为3.15%,效率的最大相对误差为3.07%。(b)出水流道进口区轴面速度场的波谷数与导叶体的叶片数相同。(c)随着流量系数的减小,出水流道进口区的轴面速度场的波峰特征越趋明显,轴面速度的尾迹特征逐步增强。(d)水流经出水流道扩散,速度逐步减小而压力逐渐增大,出水流道进口区的脉动主频受叶轮旋转的影响很小,压力波动主要受导叶体进口流态和导叶体结构的双重影响。(e)不同工况时各监测点的主频及次主频均为低频脉动。

Analysis on the unsteady pressure and velocity in the inlet region of outlet conduit of a tubular pumping system

In order to study the unsteady pressure and velocity of the inlet region in the outlet conduit for the S-shaped shaft tubular pumping system, the whole flow passage of the pumping system was simulated based on the CFD technology. Comparison of numerical simulation results and experimental values under different operation conditions verifies the accuracy of the numerical model. The results show that, the maximum relative deviation of head coefficient is 3. 15%, and the maximum deviation of efficiency is 3. 07% in the range of simulated operating conditions compared with the experimental data. The distribution of axial velocity is affected by the number of the guide vane blades in the circumferential direction, and the wave trough number of the axial velocity filed in the circumferential direction is the same as the guide vane blade number. With the decrease of flow rate coefficient, the wave peak characteristic of the axial velocity filed is more obvious, and the wake characteristics increases gradually as well. When water flows through the outlet conduit, the pressure will increase and the velocity will decrease gradually. The rotation speed of impeller has little effect on the main frequency of inlet region in the outlet conduit. Both the inlet flowing pattern and flow improvement of guide vane have effects on the pressure fluctuation. The main and secondary frequency of every monitoring points are low frequency pulsation in different operating conditions.