Computational and experimental study of no in an axisymmetric laminar diffusion flame

In this study, we extend the results of previous combined numerical/experimental investigations of an axisymmetric laminar diffusion flame in which spontaneous Raman spectroscopy, laser-induced fluorescence, and a multidimensional flame model were used to generate profiles of the temperature and major and minor species. We discuss issues related to the computation and measurement of NO in an unconfined laminar flame in which a cylindrical fuel stream is surrounded by a co-flowing oxidizer jet. Computationally, the governing conservation equations of mass, momentum, species, and energy were solved with detailed transport and finite-rate chemistry submodels to predict the velocity, species mass fractions, and temperature fields as functions of the two independent spatial coordinates. A discrete solution was obtained on a two-dimensional grid by employing Newton's method with adaptive mesh refinement. The computations were performed in both serial and parallel using up to 32 processors of an IBM SP2. Experimentally, NO radical concentrations were measured using laser-induced fluorescence. The associated results of the computational study clearly indicate that the prompt production path is the dominant formation route of NO. Thermal NO and the N₂O submechanism play minor roles in total NO production. Excellent agreement was obtained for the structural features of the computed and measured NO. The peak NO mole fractions agreed to within 30% of the experimental value. Additional quantitative CH computations and measurements are essential for further study of this problem.