Research On Hydrodynamic Noise Of Multistage Centrifugal Pump

Pump is an important fluid machinery. The multistage centrifugal pump studied in this paper is mainly used for urban water supply and residential water, which not only achieves excellent hydraulic performance, but also has higher requirements for noise reduction.Aiming at the hydrodynamic noise of multistage centrifugal pump, four-stage centrifugal pump was selected as the research object to analyze the internal flow, pressure pulsation,modal and acoustic field. The main research contents and conclusions are outlined as follows:(1)The research situation pump noise was summarized to determine research contents of the topic. A hybrid algorithm combination computational fluid dynamics with computational acoustics was adopted to analyze and study the hydrodynamic noise of multistage centrifugal pump(2)A computational fluid dynamics(CFD) code was employed to simulate the three-dimensional internal steady flow. It is shown that the predicted pump performance curves present good agreement with the experimental ones, indicating the numerical prediction of performance is correct and reliable. Static pressure and turbulent energy distribution in the pump were analyzed. It shows the head of first stage is higher than that of other stages and rotor-stator interaction has a significant influence on the hydraulic performance.(3)Based on the steady simulation, unsteady simulation was carried out to analyze pressure pulsation. The basic frequency in the channel of impeller is relevant to diffuser blades number and it is the strongest near the impeller outlet, while the basic frequency in the channel of diffuser is relevant to impeller blade number. In the channel of diffuser, the pressure pulsation close to the diffuser inlet is more intensive and the amplitude in front channel is higher than that in rear channel. In addition, the amplitude of frequency which is least common multiple of impeller’s frequency and diffuser’s frequency was found to be enhanced.(4)The finite element method(FEM) was adopted to calculate the modal of impellerand multistage centrifugal pump, which acquired natural frequencies and vibration modes.(5) The direct boundary element method(DBEM) was adopted to calculate the sound field in the interior pump. The blade rotating dipole and diffuser dipole were conducted as the noise source. Then, sound pressure level distribution under different quantities of flow was compared to analyze the characteristics. In addition, the monitoring points were set in the pump inlet and outlet to analyze frequency response curves. It shows the basic frequency is impeller’s frequency and triple impeller’s frequency. Otherwise, the double impeller’s frequency has a high amplitude. The triple impeller’s frequency is also double diffuser’s frequency, so the amplitude of this frequency is strengthened.(6)The finite element method(FEM) was adopted to calculate vibro-acoustic field in the exterior pump. Directivity field points, plane filed points and spherical field points were set outside the multistage centrifugal pump to analyze sound pressure distribution under different quantities of flow. The basic frequency is impeller’s frequency,while the second basic is double and triple impeller’s frequency.(7)According to the simulated result, impeller structure has a significant to the hydrodynamic noise of multistage centrifugal pump. In order to improve the hydrodynamic performance and reduce noise, experiments were compared as a reference. In the case of acquiring high hydrodynamic performance, reducing impeller diameter or blade diameter appropriately can reduce noise.