CARS Diagnostics of High Pressure Combustion - 2. Measurements of NO, H2O and High Pressure Flames

Spectroscopic investigations into the coherent anti-Stokes Raman spectroscopy (CARS) spectra of N0 and H20 and were conducted the capability of CARS for diagnostics of high pressure flames. CARS is a remote laser diagnostic technique for temperature and species measurements in hostile combustion environments. As such it possesses considerable relevance to the Army in the general areas of ballistics and propulsion. This report describes the results of investigations conducted into the effects of high pressure, specifically the phenomenon of collisional narrowing, on CARS spectra from which temperature and density information derive. Experimental studies of CARS spectra were conducted in NO in a heated, high pressure cell over the range 300K-800K, 1-33 atm, in H2O from 500K-1000K, 5-30 atm and in a high pressure, premixed C0/air flame from 1-15 atm. The CARS spectra obtained were used to evaluate the CARS computer code. in addition, a new technique, termed dual broadband CARS, was developed which permits the simultaneous detection of a multiplicity of chemical species. This approach removes the nominal limitation on CARS of interrogating just a single constituent at a time. This technique should prove invaluable in the transient environments of combustion p High pressure combustion diagnostics; Collisional narrowing; Water vapor; Nitric oxide; High pressure premixed flame; and Polarization suppression.