Investigation on the flow-induced noise propagation mechanism of centrifugal pump based on flow and sound fields synergy concept

This paper explores the flow-induced noise propagation mechanism of centrifugal pump from the view of flow and sound field synergy concept. First, the unsteady synergetic relationship between flow and sound fields is deduced, and the synergy angle is defined to describe the synergy degree. It is shown that the domain-averaged synergy angle (theta(ave)) changes little with flow time, which implies that the synergy degree is basically unchanged with flow time. With increasing rotational speed or flow rate, the time-averaged theta(ave) (theta(tave)) in the impeller and the volute moves far away from 90 degrees gradually, i.e., the synergy degree increases. Meanwhile, the noise outside the pump increases, and the variation of both the noise outside the pump and theta(tave) tends to be gradual. The results manifested that the flow-induced noise propagation mechanism of the centrifugal pump can be well described by the change in synergy degree and the increase in synergy degree can cause the noise tending to propagate outside. In addition, the impact of the blade outlet angle on the noise propagation characteristics is investigated. Considering the synergy degree in the impeller and the volute comprehensively, the deviation of theta(tave) from 90 degrees decreases from 6.48 degrees to 4.74 degrees as the angle increases from 15 degrees to 35 degrees, i.e., theta(tave) tends to approach 90 degrees, and the synergy degree decreases gradually, indicating that increasing the blade outlet angle can weaken the tendency of noise propagating outside by decreasing the synergy degree. These conclusions can guide noise control research and engineering design.