Hydrodynamic cavitation of binary liquid mixtures in laminar and turbulent flow regimes

Abstract

Hydrodynamic cavitation of several binary liquid mixtures (diethyl ether – 2-butanol, diethyl ether – ethanol, water – isopropanol) has been performed at different relative mass fractions. Different cavitating flows have been studied downstream two sorts of constrictions: micro-diaphragm profiles, that correspond to shear rate induced cavitation, and micro – venturi profiles, that correspond to sheet cavitation. Using microsystems as ‘labs on chip’ has made possible these investigations, with a low amount of the mixtures. Moreover, these microsystems have also made possible the inception of cavitation from a laminar single phase flow, because of the small hydraulic diameter of the orifices. Characterization of the binary liquid mixtures is presented with the help of σ(Re) diagrams, where σ is the cavitation number and Re is the Reynolds number in the constriction. It has been observed that when the inception of cavitation arises from a laminar single liquid phase regime at a fixed pressure drop, the flow rate is then slightly increased. Moreover, an anomalous behaviour of the pure ethanol liquid has been consistently recorded, with both types of devices. The presence of diethyl ether in the mixture may aid the inception of cavitation because it increases the vapour pressure of the blend and lowers its viscosity. The presence of isopropanol in water increases the viscosity of the blend and shifts the inception of cavitation towards lower Reynolds numbers. The shape of the constriction has also revealed to be a major parameter associated to the two phase flow transition of the mixtures.