אתר החוקר

A centrifugal pump of high specific speed with a diagonal type of impeller flow is studied experimentally and numerically. 2D and 3D numerical methods are used with applying acoustics - vortex equations. Measurements show that in the beginning of the volute, in the pseudo-sound zone, the amplitude of the Blade Passing Frequency (BPF) spectral component is higher than the one at the pump's outlet by an order of magnitude. The 3-Dimensional analysis gives a good agreement with experimental data while the 2D prediction underestimate the BPF amplitude in the beginning of volute but provides the correct value at the outlet of the pump. The flow patterns in the impeller and volute of such a pump have essentially 3D pattern. A strong unsteady 3D spiral motion of the fluid takes place in the beginning of the volute. It produces powerful pseudo-sound perturbations. The amplitude of pressure pulsation reduces rapidly downstream to the level of acoustical oscillation in the form of plane wave. It is concluded that experimental validation confirms that 2-Dimensional method can be used for prediction of propagating acoustical oscillation but it underestimates the amplitude of pseudo-sound oscillation in the volute. In this zone the new 3-Dimensional method must be used for centrifugal pumps with high specific speed level.