Effect of the volute tongue cut on pressure pulsations of a low specific speed centrifugal pump

Abstract

The volute tongue, as the crucial component inducing rotor-stator interaction, is detrimental to unsteady pressure pulsations of centrifugal pumps. In the present paper, to investigate the effect of the volute tongue cut on pressure pulsations of a low specific speed centrifugal pump, three volute tongues are obtained through twice cuts, named cases 1, 2, 3. Twenty measuring points are evenly mounted on periphery of the volute casing to obtain unsteady pressure signals using high response transducers. Pressure amplitudes at the blade passing frequency fBPF and root mean square (rms) values in 0 Hz-500 Hz frequency band are applied to evaluate the cutting effect. Results show that pressure spectrum is significantly affected by the volute tongue cut, especially for the component at fBPF. For different measuring points, influences of the volute tongue cut on three cases are not identical. From rms values, it is evident that cutting the volute tongue will lead to pressure energy increasing for most of the concerned measuring points, especially for the points at the far away region from the volute tongue. Finally, from comparison with the original shape case 1, the averaged increment of the twenty points is more than 20%. So it is concluded that for this type centrifugal pump, cutting the volute tongue is not reasonable considering low pressure pulsation requirement.