Interaction of co-current gas flow with near-wall liquid film inside a nozzle (cylindrical channel) under ejection into vacuum is studied experimentally. Local parameters of near-wall films of ethanol, water and their mixtures under interaction with co-current air flow are measured with the help of capacity-type probes. It is shown that under conditions of experiments carried out co-current flow exert strong dynamic impact on near-wall liquid film, leading to intensive wave formation, detachment of droplet and their dispersal by co-current flow. It is found that the amount of liquid entrained from boundary surface can reach over 50 % from the initial flow rate of liquid. Flow structure of gas-droplet jet arising under ejection into vacuum is visualized with the help of laser illumination. Appearance of droplets backflows (at angles over 90 with respect to nozzle axis) is shown. Temperature of the film formed on the nozzle external surface is measured. It is shown that the film of liquid is cooled down to the temperature at which its saturated vapor pressure becomes equal to pressure in vacuum chamber.
Abstract. The problem of joint gas outflow with near-wall liquid film from an axisymmetric cylindrical channel into vacuum is studied experimentally. It is shown that liquid film at the exit edge of the channel not only disintegrates into droplets, but also emerges on the external surface of the channel and starts moving in the opposite direction to the gravitational force. The phenomenon revealed is strongly dependent on physical properties of liquid and pressure in the surrounding space. Temperature of a film formed on the external surface of the channel is measured. It is shown that due to evaporation in vacuum liquid film is cooled to temperature at which the saturated vapor pressure is close to pressure in vacuum chamber.
Outflow of a near-wall liquid film with co-current gas flow from a nozzle (cylindrical channel) into vacuum is studied experimentally. Special features of near-wall liquid films ejection into vacuum are established with the help of the developed measurement techniques (droplet phase flow structure visualization with ordinary and laser illumination, deposition of droplets on paper substrates, spectrophotometry): turn of the film in the opposite direction at the nozzle lip and its rise along the outer surface of the nozzle against gravity, cooling due to evaporation, disintegration into droplets with the formation of the spatial flow structure, which includes two typical areas: central and peripheral. The temperature of the liquid film formed on the outer surface of the nozzle is measured. It is shown that the film is cooled down to a temperature at which the pressure of liquid saturated vapors becomes equal to the pressure in the vacuum chamber. The distribution functions of droplets by size, direction of fly, and velocity in the peripheral area of the flow are obtained.
The results of experimental study on high-velocity co-current gas flow interaction with near-wall liquid film are presented in the paper. Local parameters of near-wall liquid film are measured with the help of capacity-type probes. It is shown that co-current gas flow has strong influence on near-wall liquid film, leading to intensive wave formation, detachment of droplets from the film surface and their entrainment by the gas flow. A model for the film motion with co-current gas flow, linking together thickness and velocity of the film with value of shearing stress at gas-liquid boundary, is suggested.
Abstract. The problem of joint near-wall liquid film ejection with gas flow from a cylindrical channel into vacuum is studied experimentally. A new technique for measuring thickness and velocity of the liquid film inside the channel with the help of capacity-type probes is presented. It is shown that co-current gas flow has strong impact on the near-wall film, leading to intense wave formation, detachment of droplets from the film surface, and formation of dry spots.
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