An Experimental Investigation on Periodic Characteristics of Gaseous Cavitating Flow in Hydraulic Valve Orifices

A visual experimental model with sheet light is established to study the difference between oil's gaseous cavitation and water's vaporous cavitation in hydraulic valve orifice under a high pressure difference and a high speed transient flow condition and to clarify the shape and periodic behavior of gaseous cavitating flow in hydraulic valve orifice. The experimental model enlarges the structure of V-shaped throttle groove with non-full-cycle opening by 2.8 times, and adopts lapping surface seal to ensure the pressure bearing capacity up to 4.5 MPa. Experimental images obtained by a high-speed camera are grayed and scaled by gray processing, and the cavitation types of valve ports under different pressure gradients and the periodic characteristics of cavitating flow in oil media under different pressure differences are studied based on Bunsen solubility, saturated vapor pressure and Strauhal number. Experimental results show that attached cavitation, cloud cavitation and atomized cavitation concurrently appear in the V-shaped valve orifice when the pressure difference is above 2.0 MPa. When the pressure difference is in the range of 2.0 MPa to 3.0 MPa, the evolution of cavitating flow is dominated by the mechanism of air release. The law that the inertia of cavitation and the period of flow increase with the increase of pressure difference is similar to water cavitation. However, when the pressure difference increases to the range of 3.5 MPa to 4.5 MPa, the gas expansion mechanism plays an important role in the evolution of cavitating flow, and the period of the attached cavitation is basically unchanged, and is different from that of water cavitating flow. © 2019, Editorial Office of Journal of Xi'an Jiaotong University. All right reserved.