Development of Advanced Optical Diagnostics to Study Cavity Flame Stabilization in a Dual-Mode Scramjet 9 views

Scramjet engines are a promising technology for hypersonic propulsion due to their high specific impulse and ability to operate over a broad range of flight conditions. However, achieving engine stability is difficult in the dual-mode regime, where the flow in the combustor is transonic. Dual-mode scramjets may experience flame blowout or mode transitions due to combustion instabilities and varying inlet conditions. Flame stability in this regime is not well understood, and must be studied for the design of reliable engines. Quantitative measurements of thermodynamic properties are needed to better understand supersonic combustion, aid validation and advancement of numerical models, and expedite development of scramjet technology. Optical diagnostics are particularly useful as they can provide off-body information, are non-intrusive in nature, and can produce spatially- and temporally-resolved quantitative thermodynamic data in reacting flowfields. In this work, optical diagnostics novel to the field of supersonic combustion are developed and implemented to investigate flameholding differences between two fuel injector configurations in a dual-mode scramjet combustor with a cavity flameholder. These diagnostics include reconstructions of the average three-dimensional flame contour in the engine using a dense array of hydroxyl radical planar laser-induced fluorescence (OH PLIF) measurements, visualization of the reaction zone using methylidyne (CH) C-X PLIF, measurements of temperature and relative species concentration throughout the combustor using hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering (fs/ps CARS), and joint statistics of simultaneous fs/ps CARS and OH PLIF measurements.

PHD (Doctor of Philosophy)

Scramjet; Laser diagnostics; Supersonic combustion

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2026-04-23