Active Control of Pressure, Sound and Velocity of Centrifugal Pumps
Abstract
Measurements of velocity, pressure and sound have been obtained in a centrifugal pump with a four blade impeller rotating at speeds between 1470 rpm and 3510 rpm to improve understanding of noise generation and to investigate the feasibility of reducing fluid dynamic noise with active control. The velocity results show flow separation in the region near the shroud wall and at the suction surface of the blades with the flow driven inward by the adverse pressure gradient near the shroud wall. The frequency spectra of the pressure distributions obtained inside the pump casing at 3510 rpm showed a dominant frequency of 50 to 60 dB above the background level associated with the blade passing frequency of approximately 240 Hz. However, the saw-tooth waveform observed in the pressure characteristic also comprised of second and third harmonics of 45 to 55 dB and 35 to 45 dB above the background level and another 8 higher harmonics with diminishing amplitude as the frequency increased. The pressure distribution underwent a circumferential variation which was believed to stem from resonance or suppression of the 11 harmonic frequencies due to circumferential variation of the geometry of the scroll. All the waveforms inside the pump were generated by 11 sinusoids of different amplitudes. Only the first three harmonics contained sufficient energy to produce a detectable signature in the air-borne noise characteristics. Consequently, there were some difference between the waveforms of the pressure and air-borne noise distributions. Intermediate maxima and minima were evident in air-borne noise characteristics but not in pressure distributions. This was due to the absence of the low amplitude high harmonic frequencies which had an effect of smoothing the waveform.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1992
- Accession Number
- ADA249446
Entities
People
- D. G. Tse
- H. Mcdonald
- J. S. Sabnis
- James H. Whitelaw