With the vigorous promotion of the national strategy for hydraulic engineering, a demand for mixed-flow pump in infrastructure has been increasing for years. As a kind of high-performance pump, the high specific speed mixed-flow pump has the advantages of stable performance and wide application area. With the increasing of specific speed, the high specific speed mixed-flow pump has begun to replace the axial-flow pumps in some application areas in recent years. It is necessary to optimize the impeller performance for it affects the pump performance directly. The velocity torque distribution along mixed-flow pump impeller is a significant parameter, which plays an important role in energy conversion between impellers and fluid. In the design of dualistic theory of mixed-flow pump impeller, the regulation of velocity torque distribution should be defined. But, there is no uniform method of expression as well as specific rule for designers to follow, and too much experience is needed to rely on. It has far-reaching meaning for the promotion of the level of mixed-flow pump design and the performance by establishing the optimization parameter model of velocity torque distribution along impeller. In order to further research the hydraulic performance of optimization method for high specific speed mixed-flow pump, a mixed-flow pump whose specific speed is 803 was chosen as the research object, and the commercial software CFX and the shear stress transport turbulence model were applied to compute the interior flow field within the pump. In this paper, the efficiency and the head were chosen as the optimization objectives, and 3 parameters that describe the velocity torque distribution were chosen as the optimization parameters, which were used to parameterize the impellers. The uniform design was adopted to arrange the sample space, the RBF (radial basis function) neural network was used to fit the relationship between the variables and objectives, and finally the NSGA-Ⅱ genetic algorithm was used for multi-objective optimization. Moreover, the difference of the internal flow field was obtained by comparing the initial linear distribution individual with the optimal efficiency individual and the optimal head individual respectively, which were selected from the Pareto solutions. The velocity torque distribution and the change trends of the wrap angel along the axial plane streamline between the initial and optimal individual were analyzed. The wrap angel values of optimal efficiency and optimal head were 75.15° and 67.85°, respectively. The variation trends of the wrap angel of micro-element based on optimal efficiency individual were contrary with the initial one, while the variation trends based on optimal head individual were the same as the initial one, but the change range was enlarged. Compared with the initial linear distribution individual, the efficiency of the optimal efficiency individual was improved by 1.12% through experimental verification. Distribution maps of the relative streamline, velocity and static pressure of the impeller guide vane at 0.5 times blade height and the static pressure of the corresponding chord length at 0.2, 0.5 and 0.8 times blade height were showed. And, the possible reasons for the differences between initial individual and optimal individuals were given. It was found that, utilizing the RBF neural network combined with NSGA-Ⅱ genetic algorithm, the effect of optimizing the impeller hydraulic performance of high specific speed mixed-flow pump was remarkable. The research provides a certain theoretical reference for further improvement of the performance of high specific speed mixed-flow pump.%为进一步探索优化高比转速混流泵水力性能的方法，该文选用比转速为803的高比转速混流泵为研究对象，运用商用软件ANSYS CFX 15.0，选取剪切应力传输（shear stress transport，SST）湍流模型对其内部流动进行计算。以高比转速混流泵的水力效率、扬程为优化目标，采用给定沿叶轮叶片轴面流线的速度矩的分布规律来实现对叶片的间接参数化，以描述该速度矩分布的四次多项式的3个参数为优化变量。采用均匀试验设计安排样本空间，利用径向基函数（radial basis function，RBF）神经网络拟合优化变量与优化目标间的映射关联，最后结合NSGA-Ⅱ遗传算法进行多目标寻优，取效率最优个体和扬程最优个体与初始模型进行分析：得到了上述3个个体的速度矩分布规律与各微元段包角沿轴面流线的变化趋势，效率最优与扬程最优时叶片包角，即各微元段包角之和，分别为75.15°、67.85°。给出了0.5倍叶高处叶轮导叶的相对流线、速度、静压分布以及0.2倍、0.5倍、0.8倍叶高处叶片相对弦长的静压分布。试验证明，效率最优个体的效率较初始个体提高了1.12%，与CFD（计算流体动力学，computational fluid dynamics）计算结果1.33%接近。该优化方法改善了叶轮的水力特性，提高了高比转速混流泵的性能，为高比转速混流泵的优化设计提供了参考。
展开▼
