NTB型陶瓷多级泵内部流动的三维数值模拟

3D numerical simulation of internal flow in NTB multi-stage ceramic pump

根据CAD水力设计对NTB型陶瓷多级泵进行三维造型及网格划分,应用CFX软件,基于雷诺时均N-S方程,采用标准k-ε湍流模型和多重参考坐标系,对该泵包括额定工况点在内的9个工况点下的内部流动进行了数值模拟,得到了静压分布图、速度矢量图、流线图等,定性分析了大、小流量和额定工况点下的内部流动规律,并预测了泵的性能曲线,模拟结果表明:设计工况下绝对速度分布较合理,蜗壳出口未发现回流,反导叶出口流速相差不大且方向基本相同,但其内部发现较大的轴向旋涡;由于叶轮与径向导叶、蜗壳隔舌的相互作用,两级叶轮中间截面流线均呈现局部非对称性,3种工况下首级叶轮均存在不同程度的射流-尾迹现象,且在小流量工况下叶片工作面处发现轴向旋涡.在此基础上于某厂试制了NTB型陶瓷多级模型泵,进行外特性试验,并将试验结果与模拟结果对比,发现试验结果与数值计算结果基本吻合,模型泵满足设计要求,NTB型陶瓷多级泵研制成功,同时,模拟结果可为今后的优化设计提供依据.

The 3D modeling and grid meshing of the NTB multi-stage ceramic pump were achieved referring to the CAD hydraulic design. Based on the Reynolds Time-Averaged N- S equations with the standard k- ε turbulence model in the multiple reference frame,the internal flow in the multi-stage ceramic pump under nine different working conditions including design point were simulated by using CFX software. The static pressure contours,velocity vectors and streamlines were obtained. The principles of the internal flow under large flow rates,small flow rates and design condition were qualitatively analyzed,meanwhile,the performance curves of the pump were drawn. The simulation results show that the distribution of absolute velocity vector under design working condition is reasonable. No backflow is found in the outlet of the volute. The velocity in the outlet of reverse diffuser changes little and the velocity vector is uniform,but axial vortex occurs there. The streamlines in the middle sections of both impellers are asymmetric. There are different scales of jet-wake structures in the first-stage impeller under three working conditions and axial vortex is found under small flow rate conditions. Based on the simulation,the model of the NTB multi-stage ceramic pump was manufactured,and the hydraulic characteristics were tested. The results of simulation and experiment were compared. The computational and experimental results present good agreement and the model pump satisfies the design requirements which show that the NTB multi-stage ceramic pump is successfully developed. Meanwhile,the results of simulation can provide foundation for optimization design.