Development of a Premixed Combustion Capability for Dual-Mode Scramjet Experiments.

Hypersonic air-breathing engines rely on scramjet combustion processes, which involve high-speed, compressible, and highly turbulent reacting flows. The combustion environment and the turbulent flames at the heart of these engines are difficult to simulate and study in the laboratory under well controlled conditions. Typically, wind-tunnel testing is performed that more closely approximates engine development rather than a careful investigation of the underlying physics that drives the combustion process.

Coherent anti-Stokes Raman spectroscopy measurement of ethylene in combustion.

Width-increased dual-pump enhanced coherent anti-Stokes Raman spectroscopy (WIDECARS) has been developed for spatially and temporally resolved simultaneous measurement of temperature and mole fraction of most major species in ethylene-air flames. This paper describes a method to infer coherent anti-Stokes Raman spectroscopy complex susceptibility distributions of the ν band of ethylene from WIDECARS spectra measured in heated mixtures of ethylene and air, and to use such distributions to fit experimental WIDECARS spectra in an ethylene-air flame. The method is used to measure mole fraction ethylene in a dual-mode supersonic combustor burning premixed ethylene and air with single-laser-shot precision (one standard deviation) of ±0.