2011 Volume 53 Issue 166 Pages 271-283
Numerical simulation on the counterflow flame of methane-air rich-premixed gas with opposing high-temperature air is carried out by using rather complex chemistry. A sinusoidal fluctuation is added to the spout velocity in order to investigate unsteady flame behavior and to clarify the effects of various parameters on flame structure. First, the influences of average velocity and the fluctuation frequency of the spout velocity on flame structure are examined with Smooke's Skeletal chemical kinetics model. It is shown that both premixed and diffusion flames exist together and the phase lag increases with the increase in the fluctuation frequency of the spout velocity. Second, the effects of premixed flame and diffusion flame on unsteady behavior are examined by using “extended IYH-Skeletal chemical kinetics model” proposed in the present study. This novel model discriminates premixed-gas-originated oxygen atom X from opposing- air-originated oxygen atom Y, so that the consumption rates of oxygen molecules X2 and Y2 correspond to premixed and diffusion flames. It is found that the strength of diffusion flame monotonically changes corresponding to the increase of flame stretch, but the strength and location of premixed flame intricately changes corresponding to the change of spout velocity.
