Numerical and experimental investigations on the acoustic characteristics of a single-stage centrifugal pump

Authors

Christian Lehr - TU dortmund university, Germany
Pascal Munsch - Ruhr university bochum, Germany
Romuald Skoda - Ruhr university bochum, Germany
Andreas Brümmer - TU dortmund university, Germany

Abstract

The acoustic properties of a single-stage centrifugal pump with low specific speed are investigated by means of compressible 3D CFD simulations (URANS) and experiments. In order to determine the pump’s acoustic transmission and excitation characteristics, a fourpole approach in the frequency domain is used. By simulation determined transmission parameters are compared to experiments in water and air as functions of the Helmholtz number. Results indicate that the acoustic transmission characteristics within the experiments are significantly influenced by the structural compliance of the volute casing in terms of a fluid-structure interaction (FSI). A modeling approach for a one-dimensional representation of the centrifugal pump’s acoustic transmission characteristics in the time and frequency domain is applied to the current pump. As one model parameter, the effective speed of sound in the 1D model needs to be reduced to 600 m s^(−1) to account for the FSI. The agreement of simulation results and the experiments underlines the above statement about the influence of FSI. In a last step, the acoustic excitation parameter, depicted as monopole and dipole amplitudes, at two different blade-passing frequencies (fBP ≈ [111; 169] Hz) are determined for several operating points. Especially for dipole amplitudes, a good agreement between experiments and simulations can be seen. The monopole amplitudes are also in similar orders of magnitude, but show stronger deviations. The cause of discrepancies between 3D simulations and experiments is believed to be the neglected influence of FSI and surface roughness as well as the simplified reproduction of flow separation at the volute’s tongue due to the use of wall functions. A final important observation made during the numerical investigations is that the excitation mechanisms at blade-passing frequency are probably independent of the piping system’s acoustic impedance.