Combustion and Mixing of Liquid Hydrocarbon Fuel in a Scramjet Model Combustor
| This research work investigates liquid-fueled scramjet combustion and mixing with a focus on injection strategy and the development of diagnostics to interrogate mixing fields. Reliable characterization of fuel distribution is crucial, as mixing directly governs the ability to stabilize flames in supersonic crossflows.
The work is divided into two parts. Part I evaluates wall-based injection relative to strut-assisted injection with a backward-swept strut in a cavity-based combustor. Using qualitative filtered infrared imaging and chemiluminescence diagnostics, the objective was to assess strut injection as a means of enhancing fuel–air mixing and extending the stability envelope. The results show that strut-assistance promotes lateral dispersion of the plume, and enables flame stabilization beyond what can be achieved with conventional wall-based injection upstream of the cavity. Part II was carried out in an updated combustor configuration and focuses on the development of a quantitative infrared imaging method tailored to liquid fuels. This approach, which has not previously been applied to liquid-fueled scramjets, addresses challenges associated with radiance absorption and incomplete vaporization. By employing fuel surrogates at reduced enthalpy, time-averaged path density maps were obtained to characterize plume penetration, entrainment into the cavity, and downstream spreading across multiple strut injection schemes. These mixing measurements were directly related to combustion experiments, showing how entrainment characteristics explain the observed differences in flameholding capability. Together, this work demonstrates a novel application of quantitative infrared diagnostics to liquid-fueled systems and systematically evaluates fueling strategies, contributing both methodology and physical insight to the design of advanced liquid-fueled scramjet combustors. |
