Fluctuating Hydraulic Force Around a Centrifugal Impeller Due to Inlet Flow Distortin and Whirling Motion

研究了泵吸壳体和离心式叶轮侧罩之间的非定常流动行为，以了解由于进口流动扭曲和旋转运动而产生的水动力脉动。主要研究结果如下：(1)进口旋流的非定常核心使叶轮发生旋转运动。(2)进口变形对叶轮出口流动影响较大。当旋流方向与叶轮自转方向相反时，其影响最大，且叶片数给出的周期性流量脉动在出口段变大。(3)它的脉动较短地传导到吸气壳与叶轮侧之间的空间，不仅引起非定常的轴向推力，还会引起旋流运动。(4)空间内的脉动压力值随着泵送流量的增大而沿周向变化。这一现象使叶轮自转发生颤振运动。(5)上述波动是由叶轮的旋转运动引起的另一种波动。后者在靠近叶轮环的位置波动较大。(6)圆柱体内的平均压力分布可以用定常转盘模型进行粗略的预测。

Unsteady flow behavior in the space between the pump suction casing and the centrifugal impeller side shroud was investigated, to know the fluctuating hydraulic force due to inlet flow distortion and whirling motion. The following results were mainly carried out.(1)The unsteady core of the inlet swirling flow makes the impeller whirling motion.(2)The inlet distortion affects strongly the impeller outlet flow. Its effect is extreamly when the swirling direction is negative to the impeller rotation, and the periodical flow fluctuation given by the blade number becomes heavy at the outlet section.(3)Its fluctuation is conducted to the space between the suction casing and the impeller side shoroud, and causes not only the unsteady axial thrust but also the swirling motion.(4)The fluctuating pressure value in the space becomes to change in the peripheral direction with increasing the pumping discharge. This penomenon makes the impeller rotation flutter motion.(5)Above fluctuation lies on another fluctuation induced from the whirling motion of the impeller. The latter fluctuation is sharp in close to the impeller ring.(6)The avaraged pressure distribution in the radial direction can be predicted roughly with the steady rotating disk model in the cylinder.