Investigation of the Noise Induced by Unstable Flow in a Centrifugal Pump

Abstract

In order to investigate the mechanism and the characteristics of the noise induced by unstable flow in a centrifugal pump, the internal flow characteristics in the pump were numerically researched, and the acoustic pressure fluctuations at the pump inlet and outlet were experimentally investigated. Obvious corresponding relationships between the flow instabilities, the cavitation and the noise were established. It was found that the rotating stall, the backflow, the hump, the occurrence of unstable flow and the cavitation in such a centrifugal pump were effectively detected through the noise, which could help to provide fundamental information on flow instabilities and guarantee safe and steady operating conditions for the system. The recirculation and prewhirl regions in the pump upstream pipe, which were caused by the backflow and the rotation of the impeller, presented the circumferential movement with a spiral shape, causing apparent broadband fluctuations at low frequency band of the acoustic pressure. The backflow and rotating stall could also result in broadband fluctuations of the pump outlet noise, which was distributed from 100 Hz to 150 Hz. Meanwhile, the broadband fluctuations of the pump outlet acoustic pressure distributed in the low frequency range, which was produced by the occurrence of cavitation, moved to the lower frequency band as the flow rate increased. The enhanced broadband fluctuations of the pump inlet and outlet noise distributed from 1 kHz to 6 kHz were caused by the coupling between the cavitation-induced noise and the system-produced noise. The broadband fluctuations of the pump inlet noise distributed between 6 kHz and 9 kHz were regarded as the typical frequency band of cavitation in the centrifugal pump.

Numerical Study of the Effect of Splitter Blades on the Flow-Induced Noise of Hydraulic Turbine

“…Cheng et al [10] improved the noise of a centrifugal pump by cutting the outlet side of the impeller, and found that there exists an optimal cutting width to weaken the rotorstator interaction between the impeller and the volute, which effectively reduces its internal and external sound field. To study the mechanism of noise induced by unstable flow inside a centrifugal pump, Lu et al [11] analyzed it through a combination of experiments and numerical simulations and found that the noise could effectively react to the phenomena of flow stall and instability inside the pumps. Paramasivam et al [12] through studying the effect of guide vanes on centrifugal fans found that centrifugal fans with conical guide vanes radiated lower noise sound pressure levels as compared to the original model.…”

Effect of Tip Clearance Size on the Cavitation Flow and Noise Characteristics of the NACA0009 Hydrofoil

“…In the naval ship, submarine and water conservancy and hydropower engineering industry [1], TLV cavitation and the noise caused by it, especially the cavitation and vibration of hydraulic machinery [2], seriously endanger the safe operation of hydraulic machinery, and have received more and more attention and concern. When cavitation occurs, cavitation noise will significantly reduce the hiding characteristics of underwater targets, and even become an extremely important noise source for the overall underwater targets [3]. Therefore, the study of TLV, cavitation and noise plays a vital role.…”

Study on the flow pattern and pressure fluctuation in a vertical volute centrifugal pump with vaned diffuser under near stall conditions

“…At the same time, it was found that the type of stall depends on the number of impeller blades. Lu et al [17] used noise to detect instability such as stall and backflow in the centrifugal pumps and established the relationship between flow instability and noise. Shibata et al [18] found that the vortex at the trailing edge of the diffuser vanes of the multi-stage centrifugal pump hinders the flow of fluid and induces flow separation at the leading edge, and it causes the stall phenomenon.…”