Scalar Properties in the Overfire Region of Sooting Turbulent Diffusion Flames
نویسنده
چکیده
The scalar structure of the overfire (fuel-lean) region of sooting turbulent diffusion flames was investigated, considering ethylene and acetylene burning in air. Measurements and predictions are reported of the mean concentrations of major gas species and mean soot volume fractions. Predictions were based on the conserved-scaiar formalism in conjunction with the laminar flamelet approximation. The comparison between predictions and measurements was encouraging, suggesting that state relationships for major gas species, found in laminar diffusion flames, were preserved in the overfire region of the turbulent flames. Measurements also indicated nearly constant soot generation efficiencies from point to point in the overfire region for sufficiently long characteristic residence times to yield nearly universal soot volume fraction state relationships at the same conditions. However, effects attributed to finite-rate chemistry were observed at shorter characteristic residence times, causing spatial variations of soot generation efficiencies in the overfire region, with associated loss of universal soot volume fraction state relationships.
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