轴流泵变转速性能试验及内部流场数值计算

研制比转速550 r/min、转速2 900 r/min型QY90-4.4-1.5潜水轴流泵样机。通过型式及变转速外特性试验,得出轴流泵qV-H、qV-Pa和qV-η性能曲线变化规律;验证qV-H、qV-Pa曲线及各转速最优工况之间换算均不满足相似定律,泵综合特性曲线等效曲线与相似抛物线差别较大;采用计算流体力学(Computational fluid dynamics,CFD)方法进行转速对流场影响数值计算,得到不同转速下最优工况叶片表面速度和静压分布,阐明外特性变化规律内在原因;泵转速提高,叶片表面速度增大,内部流动基本符合圆柱层流面无关性假设;同时叶片所受升力增大,叶片背面所承受的负压强进一步降低,易发汽蚀的可能性增大,可以推测汽蚀是制约轴流泵高速化发展的主要因素之一。轴流泵内部液流轴向运动雷诺数较小,难以达到尼古拉兹试验粘性力相似的自动模型化区,且叶栅与单翼型升力系数的差异,也难以保持变转速工况之间升力的相似,这是不满足相似定律的主要原因。

Experiments and Numerical Simulation on Variable Speed Performance and Internal Flow of Axial Flow Pump

The QY90-4.4-1.5 submersible axial flow pump with specific speed 550 r/min and rotate velocity 2 900 r/min is developed.Through the experiment of type and the external characteristics of the variable rotational speed,performance curves such as qV-H、qV-Pa and qV-η are obtained.The conversion for qV-H、qV-Pa and the optimal condition among the variable rotational speed does not meet the proportion law of similar theory,and the affect between similar parabola of general characteristics and efficiency contour is larger.The internal flow fields on effect of the variable rotational speed are numerically simulated by computational fluid dynamics and both velocity distribution and static pressure distribution of blade surface at the various pump rotational speed are obtained.By analyzing the test data,the relation between the external characteristic and the internal flow is discussed,also the investigation results prove that the speed around the blade surface are improved with the increasing of rotational speed and the internal flow of pump can satisfy the assumptions of cylindrical flows without interference.Meanwhile it is showed that lift on the blade increases,the negative pressure on the blade suction surface further reduces and where the cavitation is prone to take place.A fact is demonstrated that viscous force and lift is changing irregularly among variable rotational speed conditions.