Abstract: The mechanism of the noise differences related to the groove-type orifices in spool valve is investigated. The experiment approaches of the pressure distribution measurement and noise measurement as well as the numerical approach of CFD analysis are used to study the noise characteristics of the groove-type orifices. The measurements of the pressure distribution are achieved by a unique designed valve unit with the sleeve shift. The study shows the noise level of groove-type orifice is mainly determined by the geometry of the groove, the direction of oil flow in grooves and the value of backpressure in the valve return chamber. Both the experimental and the numerical results of pressure distributions reveal that the noise of the groove-type orifices has close relationship with the pattern of the pressure distributions in the groove. In converging flow direction of the groove, the groove with increasing cross-section area tend to cause quite higher noise at a certain value of the backpressure, while the groove with constant cross-section can restrain the air-release inside the groove passage and shows much quiet. In diverging flow direction, the noise characteristics of the grooves are almost same, and the noise level is considerably low.

Key words: Cavitation, Experimental study, Groove-type orifice, Noise characteristics, Pressure distribution, Smooth tread, Tγ/A-wear rate, Wear prediction, Wheel wear model