THE IMPACT OF COMBINED AIR ON THE ACOUSTIC PARAMETERS OF CENTRIFUGAL PUMPSOleg Milman, Nikolay Pribaturin and Aleksey KirjukhinAbstract The paper deals with the effect of the concentration of undissolved air in the working environment of the pump on its vibration levels at various operational modes. The hydrodynamic noise (HDN) and vibronoise characteristics (VNC) of centrifugal pump during the flow of water-air mixture with finely divided air bubbles with volumetric air concentrations up to ε = 1.3% at the entrance was investigated on the experimental stand. It is shown that the concentration of ε > 1% of the pump head decreases sharply when ε ≈ 0,2 ÷ 0.22% significantly by 15 ÷ 20 dB falls hydrodynamic noise in the frequency range f ≥ 500 ÷ 625 Hz. A further increase of the volume concentration in the range of ε = 0,22 ÷ 1.2% virtually has no change of the HDN and VNC. Evaluation of natural frequencies of gas bubbles oscillations with a diameter about 1 mm lies in the region of f = 3 kHz and in this area of frequency the noise and vibration of the gas-liquid mixtures flow is significantly reduced.
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