Electronic-Resonance-Enhanced CARS for Quantitative in-situ Nitric-Oxide Measurements in High-Pressure Combustors

The primary objective of this Phase-II research effort will be to complete the development of the electronic-resonance-enhanced coherent anti-Stokes Raman scattering (ERE-CARS) technique for quantitative in-situ concentration measurements of nitric oxide (NO) in high-pressure flames. The research effort will be focused 1) on investigating the pressure-scaling laws for NO ERE-CARS at pressures up to 50 atm and at flame temperatures, 2) on demonstrating single-shot NO-concentration measurements using a broadband optical parametric oscillator (OPO), and 3) on investigating the feasibility of ERE-CARS using picosecond lasers. The development of two theoretical codes will be completed, one based on perturbation theory for the extraction of quantitative NO concentrations and the other based on the density-matrix theory for the investigation of saturation behavior of ERE-CARS. The density-matrix-based theory will also aid modeling of the picosecond ERE-CARS signal for which the standard perturbation-theory-based CARS models are not sufficient because of the transient nature of the signal. The development in the Phase-II research effort will pave the way for performing spatially and temporally resolved quantitative in-situ NO-concentration measurements in the JP8-fueled 20-atm combustor rig located at Wright-Patterson Air Force Base.