Shape design of the bottom plug used in a 3-way reversing valve to minimize the cavitation effect

Abstract

In the washing machines used for the pressure-cleaning of automotive parts, a pair of 2-way valves frequently reverses the flow direction of the water to spray high-pressurized clean water to remove all oil and dirt from machined engine and transmission blocks. Although this valve system is widely used due to its competitive price, its application can be restricted by the surging effect of a pressure ripple caused by inaccurate valve control during the rapid changes in water flow. As an alternative, a 3-way reversing valve can be used to replace the valve system, to provide rapid and accurate changes in water flow direction without the need of a precise control device. During the use of this alternative valve, however, a cavitation effect often occurs due to a complicated bottom plug shape. In this study, the cavitation index and POC (percent of cavitation) were introduced to numerically evaluate the cavitation effect. To minimize the cavitation effect, an optimal shape design was carried out via parametric study, in which a simple CAE-model was applied in order to avoid time-consuming multi-phase fluid-flow analysis and also to avoid the need for convergence, which is difficult to achieve. A full-factorial DOE and an artificial neural network model provided the optimal values required for a status of nocavitation occurrence: waist length, tail length and POC at 6.50 mm, 6.69 mm and 27%, respectively.