Investigation of fuel droplet evaporation at supercritical conditions

Document Type

Conference Proceeding

Publication Date

1-1-2026

Abstract

High-speed propulsion systems including modern gas turbine engines, scramjets, detonation engines, and rocket engines, operate at combustor conditions exceeding critical temperature and pressure for injected liquid fuels. Liquid droplets generated by high-pressure fuel atomizers undergo phase transition into vapor form in ways significantly different from well-established subcritical droplet deformation and evaporation models. A sharp liquid-vapor interface with strong surface tension influence is replaced by a single-phase Dense-Fluid Mixing (DFM) layer where transport is diffusion dominated. Species transport and fuel-air mixing have a strong influence on the efficacy and speed of combustion and heat release processes. Thus, obtaining a fundamental understanding of thermodynamics, phase change, and heat transfer at supercritical fuel injection conditions is critically important for high-speed propulsion system design and optimization. Particularly, knowledge is sought for processes involving sub-micrometer (μm)-sized droplets with high spatial (O(μm)) and temporal resolution (O(ns)). This work describes ongoing efforts to study evaporation processes of hydrocarbon fuel droplets at supercritical conditions. An experimental setup has been developed that can reproduce supercritical pressure and temperature conditions for single-and multi-component hydrocarbon fuels. Diagnostic approaches including high-speed backlit imaging, background-oriented schlieren and 2-color laser induced fluorescence for temperature measurement are under development with preliminary results demonstrated. Initial tests have been conducted with a suspended droplet at subcritical conditions. Numerical simulations have also been pursued to evaluate the applicability of standard models used at subcritical conditions for use at supercritical conditions. Overall, the present work documents the development of experimental and computational tools to probe supercritical droplet phase change and transport phenomena, which we will build upon in future work.

Publication Source (Journal or Book title)

AIAA Science and Technology Forum and Exposition AIAA Scitech Forum 2026

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