环量分布对基于反问题设计的混流泵优化结果的影响

Influence of circulation distribution on the optimization results of mixed-flow pump based on inverse design

为定量研究叶轮出口环量分布对导叶式混流泵优化结果的影响,该研究在试验验证数值模拟准确性的基础上,以反问题设计为基础,结合最优拉丁超立方抽样法,径向基神经网络模型和多岛遗传算法,以0.8Q_(des)、1.0Q_(des)和1.2Q_(des)处泵段加权效率为优化目标(Q_(des)表示设计流量),以1.0Q_(des)处扬程变化小于3%为约束条件,在自由涡设计(叶轮出口环量恒定分布)和强迫涡设计(叶轮出口环量线性变化)两种不同方案下分别对比转速为511的导叶式混流泵叶轮进行参数化优化,并对优化结果进行对比分析。研究结果表明:以轮毂处环量值作为翼展方向环量分布控制参数,结合连续性方程、能量方程和径向平衡方程,对叶轮出口处环量分布进行计算是可行的;局部敏感性分析表明环量控制参数对优化结果具有较大影响,在优化设计中应该被考虑;自由涡设计优化结果的加权效率为84.14%,而在强迫涡设计中该加权效率为85.08%,且两者扬程均满足约束条件,内流分析表明强迫涡设计中效率的提升主要由叶轮出口附近流态的改善引起。研究结果可为同类型涡轮机械的优化设计提供参考。

To quantitatively study the influence of the impeller outlet circulation distribution on the optimization results of the mixed flow pump,the mixed flow pump with a specific speed of 511 was selected as the baseline model.A comprehensive optimization system was used to optimize under two different conditions,and the performance of the optimization results were compared with the baseline model.In the first case,the influence of the distribution form of the impeller outlet circulation on the optimization result of the mixed flow pump impeller was not considered,that is,the free vortex design(constant distribution of impeller outlet spanwise circulation)was adopted,while in the second case,the effect of circulation distribution was considered,and the forced vortex design(linear distribution of impeller outlet spanwise circulation)was adopted.The optimization system consists of an inverse design method,an optimal latin hypercube sampling method,a radial basis function neural network model and a multi-island genetic algorithm.The optimization objective is the weighted efficiency at 0.8Q_(des),1.0Q_(des) and 1.2Q_(des) with weighting factors of 0.2,0.5,and 0.3(Q_(des) means design flow rate).The constraints are the head change of the optimized mixed flow pump at 1.0Q_(des) less than 3%compared to the baseline model design point,and the pump section efficiency at 0.8Q_(des),1.0Q_(des) and 1.2Q_(des) is greater than the baseline model.The research results showed that in the forced vortex design,when the circulation value at the hub was selected as the design parameter,it is feasible to combinedly use the continuity equation,the energy conservation equation and the radial balance equation to calculate the spanwise distribution of impeller outlet circulation.Which can ensure that the pump section head changes of the sampling points under the design condition are within a reasonable range(the range of head variation is less than 10%of the baseline model design head),and there is no need to add new sample points.In addition,the comparison of the predicted head and calculated head of the optimal solution also shows the same result.The results of local sensitivity analysis showed that the impeller outlet spanwise circulation distribution control parameters has a greater impact on the pump section weighted efficiency,and it can influence the other design parameters effect on the weighted efficiency.Therefore,it is necessary to consider the influence of the impeller outlet circulation in the optimal design of the mixed flow pump.The internal flow analysis showed that the forced vortex design can more effectively control the flow regime near the impeller outlet than the free vortex design.This is not only conductive to the improvement of the efficiency of the impeller,but also to the reduction of the hydraulic loss of the downstream components of the impeller,thereby further improving the overall optimization effect of the mixed flow pump.In the free vortex design,the weighted efficiency of the optimization result is 84.14%,while in the forced vortex design,the weighted efficiency of the optimization result is 85.08%,and the heads of both all meet the constraint conditions.This study can provide reference for the optimization design of turbomachinery,so as to maximize the optimization effect.