Mean and Fluctuating Radiation Properties of Nonpremixed Turbulent Carbon Monoxide/Air Flames

Mean and fluctuating spectral radiation intensities were measured for horizontal chordlike paths through turbulent nonpremixed carbon monoxide/air flames. Measurements in the 2700 nm radiation band of carbon dioxide revealed radiation fluctuations exceeding 50 percent in some locations even though mean radiation levels were not strongly influenced by turbulence/radiation interactions. Both time-independent and time-dependent stochastic simulations were developed to treat turbulence/radiation interactions as well as the temporal properties of flame radiation. The stochastic simulations were based on the laminar flamelet concept to relate scalar properties to mixture fracture, methods analogous to statistical time-series techniques to treat the probability density functions and spatial and temporal correlations of mixture fraction along the radiation path, and a narrow-band radiation model. The simulations yielded encouraging predictions of mean and fluctuating values, probability density functions, and temporal power spectra of spectral radiation intensities.