Experimental study of multiphase flow occurrence caused by cavitation during mineral oil flow

The article focuses on the experimental determination of the amount of released gas due to cavitation using an optical evaluation method. Cavitation is induced by the mineral oil flow through a throttle valve which characterizes commonly used valves in oil hydraulic systems. Cavitation zones are influenced by the defined experimental conditions. The influence of flow velocity, downstream pressure, and valve displacement on the development of gas phase due to cavitation is evaluated. Depending on the defined experimental conditions and the throttle valve displacement, a specific amount of released gas phase is monitored in the assembled observation window. The results give an overview of the amount of gas phase in the form of the bubble size distributions, volume and mass fractions that are released from the mineral oil when cavitation occurs under the defined experimental conditions. With respect to empirically acquired data, it can be said that the volume and mass fraction evolution of released gas phase, depending on the cavitation number, can be suitably described by a power law with an appropriate order of scaling. At the same time, a change in the determined curves during the initial phase of cavitation is found. Based on measured data, it can also be said that depending on the experimental conditions, up to 1 vol. % of air is present in the assembled observation window. It is also determined that up to 8% of air is released from the dissolved state depending on the achieved experimental conditions.