The report gives results of a detailed examination of four techniques for practical combustion diagnostics: spontaneous and near-resonant Raman scattering, laser fluorescence, and coherent anti-Stokes Raman scattering (CARS). For diagnosis of highly luminous, particle-laden flames (e.g., in hydrocarbon-fueled primary combustion zones), spontaneous and near-resonant Raman scattering appear to possess a low probability for successful application, even with advanced state-of-the-art laser sources. However, for clean flame diagnostic or probing or environments with modest particulate levels (e.g., some secondary combustion and exhaust/plume regions), spontaneous Raman scattering is very attractive due to its simplicity, high level of understanding, and advanced state of development. Laser fluorescence appears capable of species concentration measurements to 10's of ppm for selected molecules whose absorptions can be saturated. In this way, fluorescence magnitudes do not depend on quenching effects. CARS appears to be capable of sucessful thermometry and majority constituent measurements in practical flame environments, although some jeopardies need to be experimentally investigated. Potential detectivities in the 10-100 ppm range may be possible using sophisticated variants of the CARS technique.

Prepared by United Technologies Research Center under contract no. 68-02-2176, program element no. EHE624 for the Environmental Protection Agency, Office of Research and Development. Issued June 1977. Includes bibliographical references (p. 132-146).