Investigation of NH 3 -H 2 Counterflow Diffusion Flames Using Dual-Pump Coherent Anti-Stokes Raman Scattering (DPCARS)

Temperature and XH2/XN2 concentration ratio measurements of non-premixed flames consisting of H2, NH3 and air within a counterflow diffusion burner using dual-pump coherent anti-Stokes Raman scattering (DPCARS) spectroscopy are reported. Experimental measurements are compared to the results of one-dimensional numerical simulations employing four different chemical kinetics mechanisms. Experimental parameters were varied to compare the kinetic mechanisms over a wider range of conditions. NH3 mole fractions of 0.26, 0.15, and 0.07 were used with varying fuel mixture flow rates. The mixture flow rates affect the flame strain rates, which are useful in determining flame stability and extinction. A majority of the experimental and simulated temperature and XH2/XN2 measurements agreed well. Discrepancies in H2 concentration occurred in four of the five flames tested. The simulated H2 concentration was overestimated in the preheat region up to 3 mm past the fuel inlet of the counterflow burner as compared to experimental results. The remaining 7 mm of flame region measured agreed well between all simulations and experimental measurements. Mean error for peak temperatures ranged between 1.5-3.2% for the four simulated measurements, which are within the same accuracy expected for the DPCARS system. Therefore, all mechanisms were comparable to experimental data. The flame with the most agreement had the lowest NH3 mole fraction, 0.07, and lowest fuel velocity.