A mixture fraction formulation is used to numerically simulate the two-dimensional structure of diluted axisymmetric methane-air nonpremixed counterflow flames. The size of the computational domain and the grid spacing are selected based on negligible differences in time-averaged quantities. The temperature and axial velocity profiles for G=0 showed reasonable agreement with the results of the one-dimensional flame code.The method is then exercised to evaluate the effects of varying levels of gravity and local strain rate. It is shown that the numerical method is capable of predicting the structure of counterflow flames in normal and microgravity environments at low and moderate global strain rates. The temperature, and axial velocity are in reasonable agreement with those calculated by the one-dimensional OPPDIF flame code. The computed structure of the zero gravity counterflow flames show large differences with those under normal gravity conditions. The computational results confirm that the peak flame temperature changes little as the ratio of the oxidizer velocity to the fuel velocity is varied.
Citation: NIST Interagency/Internal Report (NISTIR) - 6839
NIST Pub Series: NIST Interagency/Internal Report (NISTIR)
Pub Type: NIST Pubs
direct numerical simulation, flame structure, methane