Pressure pulsation characteristics and its impact on flow-induced noise in mixed-flow pump

Abstract: As a kind of pump with low head and large capacity, the mixed-flow pump is widely used in large quantities of fields including water conservancy and sewage system of municipal works and so on. The pressure pulsation and flow-induced noise of pump have become two of the most important issues which have negative effect on reliability. The pressure pulsation is the interior performance of the unsteady flow in the pump and the flow-induced noise and vibration are the exterior performance of the unsteady flow in the pump. In order to study the rules of pressure pulsation and flow-induced noise change under different flow rate conditions in a mixed-flow pump and to find the relationship between pressure pulsation and flow-induced noise, the flow field and sound field were numerical simulated. This paper used the PRO/E software to build the pump model and to use the ICEM CFD to conduct the mesh division of the calculated domain. The mixed-flow pump mainly consisted of inlet pipe, impeller, volute and discharge pipe. The unsteady flow was numerical simulated based on RANS solver and SST turbulence model. During the unsteady simulation, the mixed-flow pump rotated for 18 cycles so as to improve the simulation stability. The simulation results of the last 2 periods were used to analyze the time domain characteristics and frequency domain characteristics of pressure pulsation in the pump. And by using the pressure pulsation on the blade as noise source, acoustic Boundary Element Method (BEM) was applied to simulate the flow-induced noise of the mixed-flow pump. The simulation results show that the pressure pulsation amplitude decreases from shroud to hub both at the inlet and outlet of the impeller, and the maximum pressure pulsation appears at the inlet of impeller. So it is crucial to conduct some optimal design for the shroud location in order to weaken the pressure pulsation. Along the circumferential direction in the volute, the pressure pulsation amplitude appears to be the largest near the tongue, the pressure pulsation decreases with the increase of circular angles. And at the outlet of volute, the pressure pulsation appears approximately to be nothing which indicates the flow at this location is steady. The dominant frequency of pressure pulsation in each monitoring point of the mixed-flow pump is always the blade passing frequency under different flow rate conditions. The rotor-stator interaction between the rotating blades and the stationary volute may be the major source of flow-induced noise in the mixed-flow pump. The dominant frequency of flow-induced noise is integral effected by the pressure pulsation and the structure mode of the pump. It is easy to occur resonate between fluid domain and structure domain when the domain frequency of pressure pulsation is closely equal to the domain frequency of the structure mode. The stronger the pressure pulsation is, the more intense the radiation level of corresponding flow-induced noise will produce under the same condition. Weakening the pressure pulsation in the mixed-flow pump is an effective way to reduce the flow-induced noise. This paper has reference value for study on pressure pulsation and flow-induced noise in fluid machinery.