Features of the Flow of a Model Liquid Into a Medium With a Variable Degree of Rarefaction

Abstract

Experimental results of observing ethanol microjets expiring into a highly rarefied medium (vacuum) through a nozzle are presented. The study of the process was carried out both at the horizontal and vertical liquid stream from the source compared to the direction of gravity The residual background gas pressure in the vacuum chamber was maintained at a level much lower than the saturated vapor pressure of the working fluid at a given outlet temperature. The possibility of modeling complex processes of microfluids expiring into a medium with a given rarefied atmosphere on a compact vacuum gas-dynamic stand is shown. It is established that the long-term flow from a thin capillary or a small-diameter hole into a vacuum or a highly rarefied gas medium differs significantly from the well-studied flow modes into a dense gas medium, as well as from the pulsed flow modes into a vacuum. The paper describes the main features of the flow and the conditions for the occurrence of instability. It is shown that the long-term flow of a liquid microjet in a vacuum has a high degree of surface instability, with a large number of sudden changes in the direction, structure, and observed density. An explanation of the reasons for the destruction of the microjet (due to the combination of capillary instability and intense evaporation of superheated liquid from the surface of the jet) is proposed. The formation of surface gas caverns causing explosive destruction of the microjet with the release of vapor–liquid droplets is established.