低比转数离心泵叶轮内流场重构与模态分析

Reconstruction and Modal Analysis for Flow Field of Low Specific Speed Centrifugal Pump Impeller

针对传统离心泵水力性能优化设计的复杂性,提出采用本征正交分解-径向基函数(POD-RBF)混合代理模型方法对离心泵叶轮内流场进行重构分析。由三次Bezier曲线对低比转数离心泵二维叶片型线进行参数化控制,通过对叶片包角、进出口安放角等控制参数进行适量的扰动得到叶片型线的样本集。由叶片型线参数及叶轮CFD内流场数据构成样本的快照矢量集,根据几何相似及网格变形方法插值得到各相似节点的流场参数,依据本征正交分解法(POD)将快照集分解为一系列正交基的线性组合。由径向基函数(RBF)拟合目标叶型所对应的正交基系数,实现了对目标叶轮内流场的重构。采用POD-RBF方法对MH48-12. 5型低比转数离心泵叶轮内流场进行了重构,其压力预测均方根误差为0. 84%,速度预测误差基本在0. 5 m/s以内,流场预测所需时间约为CFD计算的1/240。对样本集进行POD基模态分析,得到了各阶基模态流场特征及能量分布特性。

According to the complexity of traditional hydraulic performance optimization design of centrifugal pump, the hybrid surrogate model method which is the combination of proper orthogonal decomposition and radial basis function was proposed for the flow reconstitution of centrifugal pump impeller. The blade of low specific speed centrifugal pump was parameterized by cubic Bezier curve, and the experiment samples can be designed by introducing small perturbation of control parameters which included wrap angle, inlet and outlet blade angles. The snapshot set consisted of the control parameter for blade shape and the flow field data. According to the geometric similarity of the impeller flow passage and the mesh deformation technology, the flow field data of the similar position were interpolated. The snapshot set can be decomposed as linear combination of orthogonal basis by using proper orthogonal decomposition. The orthogonal basis coefficients for the objective blade were fitted by using radial basis function. The flow field data of the objective impeller were reconstructed. In the calculation case for the type of MH48-12.5 centrifugal pump, the flow field in impeller was reconstructed. The root-mean-square error for pressure prediction was 0.84%, and the velocity prediction error was within 0.5m/s. The computation time for the flow field prediction was less than 1/240 of the CFD. POD base modal analysis was carried out on the sample set. The base modal characteristic of flow field and its energy distribution were analyzed.