叶轮倾斜出口对长轴消防泵内流特性的影响

Influence of inclined impeller outlet on internal flow characteristics of long shaft fire pump

以XB4.3/240-300LC型立式长轴消防泵为研究对象,在保证叶片包角、进出口安放角、叶轮出口宽度、叶轮出口中间位置到叶轮进口轴向距离以及到旋转轴的径向距离、出口过流断面面积、叶片进口边与前盖板流线交点的径向坐标值均不变的条件下,通过改变叶轮出口倾斜角度设计多种叶轮方案,采用SST湍流模型,对不同方案进行数值模拟和内部流场分析,以寻求泵水力性能最优的叶轮出口倾斜角度.研究结果表明:改变叶轮出口倾斜角度,泵扬程和效率在小流量工况下提升幅度较小,而在大流量工况下,提升幅度相对较大;当叶轮倾斜角度为15°时,泵扬程和效率出现峰值,继续增大倾斜角度,两者反而下降,则倾斜角度为15°视为最优叶轮出口倾斜角度,此时泵扬程和效率相对原始方案分别提高5.95%和1.19%;叶轮出口处绝对速度圆周分量和径向分量在大流量工况下分布有较好的一致性,叶轮出口倾斜角度对其影响较小,而在小流量工况下,各方案的绝对速度分量在流道内分布规律较差;叶轮倾斜出口对环形空间及空间导叶内部湍动能分布有较大影响.

Taking the XB4.3/240-300LC vertical long shaft fire pump as the research object,under the condition that the blade wrap angle,the inlet and outlet placement angles,the width of the impeller outlet,the axial distance from the middle position of the impeller outlet to the impeller inlet and the radial distance from the rotating shaft,cross-sectional area of outlet flow and the radial coordinate value of the intersection of the blade inlet edge and the front cover streamline were constant,various schemes were designed by changing the impeller outlet inclination angle.The shear stress transfer (SST) model was used to carry out numerical simulation and internal flow field analysis for different schemes,so as to find the impeller outlet inclination angle with optimal pump hydraulic characteristics.The results show that by changing the inclination angle of the impeller outlet,the head and efficiency increase slightly under low flow conditions,while the increasing is relatively large under high flow conditions.When the inclination angle of the impeller is 15°,the head and efficiency appear peak values.If the inclination angle continues to increase,both will decrease instead.If the inclination angle is15°,it is considered as the optimal impeller outlet inclination angle,and compared with the original scheme,the head and efficiency are increased by 5.95%and 1.19%,respectively.The circumferential and radial components of the absolute velocity at the outlet of the impeller have good consistency under the large flow conditions,and the inclination angle of the impeller outlet has little effect on it.Both components of the absolute velocity of each scheme have poor distribution regularity in the flow channel under small flow conditions.The inclined outlet of the impeller has great influence on the distribution of turbulent kinetic energy in the annular space and the space guide vane.