Flow of Ethanol into a Medium with Varying Degrees of Rarefaction
Experimental results of observation of ethanol microjets flowing into a highly rarefied medium (vacuum) through a nozzle are presented. The investigation of the outflow process was carried out both horizontally and vertically in the direction of gravity, when the liquid was expelled from the source. The condition of keeping constant the residual background pressure in the vacuum chamber is much lower than the saturated vapour pressure of the working liquid at a given temperature of the blast. The possibility of simulation of complex processes of the flow of micro-liquids in a space with a given rarefied atmosphere on a compact vacuum gas-dynamic test bench is shown. It is found that the continuous efflux from a thin capillary or a hole of small diameter into a vacuum or a strongly rarefied gaseous medium differs significantly from the well-studied modes of efflux into a dense gaseous medium, as well as from the pulse modes of efflux into a vacuum. The paper describes the main features of the flow and the conditions of the instability emergence. 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 direction, structure and observed density. An explanation for the causes of microjet failure, caused mainly by a 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 collapse of the microjet with ejection of vapor-liquid droplets is established.