Reduction of Partial-Load Rattling Noise of an Oil-Injected Screw Compressor.

Abstract

This paper describes a study of partial-load rattling noise of an oil-injected air screw compressor and its reduction method. Rotational vibrations of the male and female rotors were measured to detect the noise source. Relative rotational angle between the rotors greatly oscilated in a sharp sawtooth wave form of tooth-meshing frequency, corresponding to the rattling noise emission. The observations indicate that the rattling noise comes from the tooth separating vibration of the rotors due to decrease in the transmission torque. A rotor profile was so selected that the transmission torque never became negative even at a no-load operation, and this profile was applied to the compressor. As the result, neither rattling noise nor abnormal rotational vibrations were generated at partial load, as well as at full load.