Experimental Study of Jet Cavitation Erosion Applicable to Oil and Water-Hydraulic Equipment

Hydraulic components, such as valves, pumps, and actuators, include many narrow passages in the form of nozzles, orifices, and gaps. Cavitation can occur when jets flow from high to low pressure through such sections, making it unavoidable for jets containing cavitation bubbles to impinge on the inner walls of hydraulic components. This report summarizes a series of experiments involving erosion tests, flow visualization, and pressure measurements with hydraulic oils and municipal water. For the erosion tests, the ASTM G134, Standard Test Method for Erosion of Solid Materials by a Cavitating Liquid Jet, method of jet cavitation erosion is used to evaluate the eroded mass loss and the specimen's surface damage. The experimental apparatus consists of a stainless steel cylindrical chamber, a high-pressure hydraulic pump, and auxiliary hydraulic components. The main test parameters are the standoff distance, cavitation number, nozzle outlet geometry, specimen surface shape, and liquid type. The specimen mass is measured, and the eroded surfaces are recorded at specific intervals. For the visualization tests, an acrylic chamber and a digital video camera are used. Video frames are extracted as pictures and are processed by superposition. For the pressure measurements, pressure-sensitive films are used to estimate the pressure distributions on the impinged surfaces. The films are bonded on the specimen surface beforehand, exposed to the cavitating jets for a short period, and then analyzed using an image analysis system. Overall, by comparing the mass loss, surface damage, visualization pictures, and pressure mapping, the effects of the experimental parameters on the erosion characteristics are examined. Moreover, design approaches that are applicable to both oil and water-hydraulic components are proposed in order to reduce erosion by cavitating jets.