INVESTIGATION INTO PRESSURE DISTRIBUTION OF SPOOL VALUE WITH NOTCHES

Abstract

A novel test apparatus used to measure the pressure distribution of spool valve with notches has been designed, thus the mechanism of the noise differences related to the different notches can be investigated. Some small holes used to detecting pressure were arranged on a sleeve that can be shifted and rotated in preset locations. Several ways are introduced to minimize the internal leakage, which include the hydraulic force used to close the gaps between the sleeve and valve body, the large distance between the small holes and a high requirement of small clearances between the body, the spool and the sleeve. The effect of this test apparatus on the flow field inside the valve is limited to the minimum to improve the accuracy of the method proposed. The experimental results of pressure distribution are agreed well with the CFD results as a whole, particularly in diverging flow direction in notch (called ‘FLOWOUT’). In converging flow (call ‘FLOWIN’), the correspondence between the experiment and CFD results is not good as the former due to the numerical errors in CFD. The CFD and experimental results of two typical notches, the sloping notch (V-notch) and the notch with a passage of same cross-section areas (U-notch), was presented in this paper. As a result, it is revealed that the U-notch has a two-stage orifice characteristic that can be helpful to suppress the cavitation noise.