高效低噪无过载离心泵多目标水力优化设计

为了整体提高离心泵水力设计水平,以叶频噪声声压级、扬程、效率和轴功率这4个指标作为判断标准,首次采用权矩阵方法借助数值模拟技术对离心泵叶轮进行了多目标优化设计。各指标的数值计算采用CFD/CA(computational fluid dynamics/computational acoustic,计算流体力学和计算声学)相结合的方法进行。基于L9(34)正交试验,深入研究了叶轮直径、叶片出口安放角、叶片出口宽度和进口安放角对离心泵扬程、效率、轴功率和流动噪声的影响规律,并根据权重分析获得了一组最佳几何参数组合。通过进行优化叶轮与原型叶轮的性能对比试验,发现该优化方案全部达标,设计流量下扬程提高2.5%,效率提高3.8%,轴功率下降3.3%,出口声压级降低1.2%,验证了权矩阵数值优化方法的可行性。粒子图像测速法内流场对比试验说明:优化方案无明显"射流-尾迹"流动结构的存在,其最大速度比原型泵小6.7%,低速区的面积比原型泵大,且由于减小了叶轮外径,叶轮和隔舌间的动静干涉作用也有所减弱;高效率低噪声离心泵叶轮设计的关键是选择合理的叶轮和隔舌间隙,以减弱叶轮出口的尾流脉动。该研究为实现高效、无过载、低噪声离心泵水力设计提供了参考。

Multi-objective optimization on hydraulic design of non-overload centrifugal pumps with high efficiency and low noise

Abstract: In order to improve the hydraulic design level of centrifugal pump, 4 indicators i.e. noise level at BPF (blade passing frequency), efficiency, head and shaft power were taken as criteria, and the matrix method was firstly used in pump design field to finish the multi-target optimization of a model pump. All the indicators were calculated by the combined CFD/CA (computational fluid dynamics and computational acoustics) method, which was based on Lighthill acoustic analogy. Efficiency, head and shaft power of the pump were obtained from the flow field calculation, and sound pressure level of fluid-borne noise was simulated by the computational acoustics from flow noise source. Vibro-acoustic interaction effect between the fluid and solid wall was not taken into account during the process of fluid-borne noise calculation. The effects of the variation of impeller diameter, blade inlet angle, blade outlet angle and blade outlet width on the 4 indicators were well investigated based on the L9 (34) orthographic experiment. Furthermore, the optimum plan was selected according to the weight of each factor from the simulation. After comparing the test results between the optimized impeller and the original one, it was found that the optimum model satisfied all the standards. The head was 2.5% higher than the original model, the efficiency was 3.8% higher than the original one, the shaft power was 3.3% lower than the original model and the sound pressure level at export was 1.2% lower than the original model at nominal flowrate. It was verified that the matrix optimal method combined with the numerical simulation in pump optimization was feasible. Within the reasonable range, the gap between impeller and volute tongue was no longer the most significant factor for flow-induced noise of the pumps. Moreover, the PIV (particle image velocimetry) method was used to compare the inner flow field of the 2 models and analyze the difference to find out why the optimal impeller could supply a better performance with low noise. Non dimensional velocity related to the same volute inlet radius was used to carry out the comparison. The results showed that there was no obvious "jet-wake" flow structure existing inside the optimization mode, the optimized impeller's maximum velocity was 6.7% smaller than that of the original prototype pump, and its range of low velocity area was larger than the original pump model. Besides, due to the decreasing of the diameter of impeller, the impeller-tongue interaction effects were also weakened. All of these were the main exact reasons for the phenomenon that the optimal impeller had a lower noise. The key to design an impeller with high efficiency and low noise was to keep a reasonable gap between impeller and tongue (or diffuser), and form a better control on the flow in the impeller channels by better blade shapes so as to weaken the wake pulsation at impeller trailing edge. The research provides the theoretical and technical references for the hydraulic design of the multi-objective optimization, and especially for the new type of non-overload centrifugal pumps with high efficiency and low noise.