| Maps of pressure distribution computed from Particle Image Velocimetry (PIV) data, combined with measurements of local pressure and far field noise, are used to identify the primary sources of noise in a centrifugal pump. It is found that severe pressure fluctuations are caused by the non-uniform outflux (the jet-wake phenomena) from the impeller. The pressure also varies depending on the position of the impeller blade relative to the volute tongue. Noise peaks are generated when the pressure difference across the tongue is maximum (due to tongue oscillation) and when the wake impinges on the tip of the tongue. Based on this understanding, modifications to tongue stiffness and geometry and to impeller design are made in an attempt to reduce noise while maintaining performance. Variations in the head-capacity curves, rms noise levels and FFT spectra are examined, and the underlying flow structures and pressure fields are studied. |
