Abstract: A novel test apparatus used to measure the pressure distribution of the non-circular opening spool is proposed. Thus the mechanism of the noise differences related to the different spools can be investigated. A method using this test apparatus is also developed to measure the pressure distributions on the grooves and the walls of return chamber. This method being developed is named as “the method of the sleeve shift”. The key point of this method is to stop the leakage among these small holes. Several ways are introduced, which include the hydraulic force used to close the gaps between the sleeve and valve body, the expansion effect of the sleeve wall in the return chamber on the gaps between holes to minimize the internal leakage 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 experiment-al results are agreed well with the CFD results. The test appara-tus and correspondence methods to measure the pressure distri-bution are easy to be standardized and used for other hydraulic components with the grooves.

Key words: Flow field simulation, Non-circular opening spool valve, Pressure distribution measurement, Throttling grooves