Experimental investigation of thermal stratification subject to multi-species ullage

Cryogenic fuel tanks are subjected to external thermal loads which raise the temperature of the fluids thereby leading to convection currents of warmer layers of fluid from the wall boundaries to the liquid-vapour interface. The heat in-leak into the tank causes an increase in the mass of high temperature fluid termed as stratified propellant mass. Stratified propellant mass is considered a penalty for launch vehicles. Hence, accurate prediction of formation of stratified propellant mass and methods to nullify it in a cryogenic tank is important. Results indicate lower temperature for liquid layers when a non-condensable gas is used. Some variations in the temperature of top liquid layers with respect to pressurant gases are also observed.