100-kHz Interferometric Rayleigh Scattering for multi-parameter flow measurements.

Simultaneous multi-point multi-parameter flow measurement using Interferometric Rayleigh scattering (IRS) at 100-kHz repetition rate is demonstrated. Using a burst-mode laser and an un-intensified high-speed camera, interferograms are obtained that contain spatial, temporal and scattered light frequency information. The method of analysis of these interferograms to obtain simultaneous multi-point flow velocity and temperature measurements is described.

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.

Development of a dual-pump coherent anti-Stokes Raman spectroscopy system for measurements in supersonic combustion.

This work describes the development of a dual-pump coherent anti-Stokes Raman spectroscopy system for simultaneous measurements of the temperature and the absolute mole fraction of N2, O2, and H2 in supersonic combusting flows. Changes to the experimental setup and the data analysis to improve the quality of the measurements in this turbulent, high-temperature reacting flow are described. The accuracy and precision of the instrument have been determined using data collected in a Hencken burner flame.

Beam shaping for CARS measurements in turbulent environments.

This paper describes a new technique to mitigate the effect of beam steering on CARS measurements in turbulent, variable density environments. The new approach combines planar BOXCARS phase-matching with elliptical shaping of one of the beams to generate a signal robust to beam steering, while keeping the same spatial resolution. Numerical and experimental results are provided to demonstrate the effectiveness of this approach.

Width-increased dual-pump enhanced coherent anti-Stokes Raman spectroscopy.

Width-increased dual-pump enhanced coherent anti-Stokes Raman spectroscopy (WIDECARS) is a technique that is capable of simultaneously measuring temperature and species mole fractions of N(2), O(2), H(2), C(2)H(4), CO, and CO(2). WIDECARS is designed for measurements of all the major species (except water) in supersonic combustion flows fueled with hydrogen and hydrogen/ethylene mixtures. The two lowest rotational energy levels of hydrogen detectable by WIDECARS are H(2) S(3) and H(2) S(4).