Investigation of interfacial phenomena involved in droplet evaporation at supercritical conditions

Combustor systems in modern high-performance gas turbine engines as well as advanced propulsion systems such as detonation engines operate at fuel injection conditions well above the critical temperature and pressure of conventional hydrocarbon fuels. At these conditions, fuel droplets generated by atomizers undergo evaporation processes significantly different from subcritical conditions marked by significant reduction in fluid surface tension and distinct phase boundary separation. At supercritical states, traditional evaporation no longer occurs; instead, the fuel disperses primarily through molecular diffusion. These phase-change and mixing processes are not well understood. Particularly, the role of interfacial thermal and mass diffusion resistance and scaling of its influence with droplet size needs better understanding.



This research will pursue experimental and analytical approaches to study evaporation of liquid droplets of pure hydrocarbons at supercritical conditions. Experiments are conducted using a custom high-pressure chamber with optical access designed to reproduce supercritical environments. N-decane and n-dodecane droplets are injected into the chamber using a droplet generator, ensuring repeatable and controlled droplet generation and injection with a controlled velocity. Real-time diagnostics included high-speed imaging to capture droplet size evolution and interfacial displacement. A laser-induced fluorescence (LIF)-based approach is used to generate detailed measurements of the droplet surface temperature. Measurements varying droplet size are compared to predictions from an analytical model considering real gas effects, variable thermodynamic properties, and vapor-liquid phase equilibrium. The impact of interfacial thermal and mass diffusion and its role in evaporation rate is investigated through experimental and computational approaches.