What is the function of the inducer wheel? Under what conditions should it be used?

Horizontal multi-stage centrifugal pumps use the head generated by the impeller to boost the pressure of the subsequent centrifugal impellers. The inducer wheel requires only a very low suction head, but this improves the overall suction performance of the pump. In centrifugal impellers, when bubbles develop to a certain extent, they affect the external characteristics and lead to a decline in performance. This is because within the flow channels of the centrifugal wheel, the liquid flows from axial to radial directions (primarily radially). Since the density of liquid is higher than that of gas, under the effect of centrifugal force, bubbles in the liquid stream can easily separate and expand rapidly, thereby blocking the flow channels and causing a sharp deterioration in the pump’s suction capacity. In a centrifugal pump, the flow channels between the impeller blades are relatively long and axial in nature; the relative flow velocity is highest at the outer edge of the impeller. As a result, cavitation occurs first at the outer edge of the impeller. The liquid near the center of the impeller, under the effect of centrifugal force, compresses the cavities at the outer edge, forcing them to move axially along that edge. Once they reach the high-pressure area, they collapse, thereby **limiting the development of cavitation**. The pump’s operating condition is disrupted only when all the flow channels in the impeller are filled with bubbles (at which point the centrifugal impeller also develops bubbles and the flow is interrupted).

Simply put, the inducer theory refers to the mechanism used by high-speed pumps to prevent vacuum formation and cavitation.

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The function of the inducer wheel is to prevent cavitation and improve the suction performance of the pump! When the liquid flows through the inducer wheel, work is done on the liquid, thereby increasing its energy; this is equivalent to doing work on the liquid that enters the subsequent impeller, increasing its energy as well, and thus serving to increase the suction performance of the pump.