Features of Measurement of Local Parameters of Near-Wall Liquid Films in Supersonic Nozzles

The work presents development of a technique for measurement of the local parameters of a near-wall liquid film (film thickness, leading edge velocity, and wave velocity on the film surface) under conditions of a co-current supersonic gradient gas flow. The parameters of an ethanol film with a co-current air flow inside a supersonic conical nozzle with the Mach number M = 2.75 were measured. The decisive role of the gas flow on the parameters of the near-wall film has been shown. It has been established that phase transitions appear in the liquid film within the nozzle because the static pressure in the gas flow over the film drops below the saturated vapor pressure of the liquid.