Effect on flow field characteristics in methane-air non-premixed flame with steam addition

The present paper reports on an experimental study to determine the effect of humidity on the flow field and the flame stability limit in turbulent nonpremixed flame, and examines the dynamical behavior of the unsteady aerodynamic flow structures observed on a bluff-body burner at both humid and non-humid air combustion states. Particle image velocimetry (PIV) is used to capture the instantaneous appearance of vortex structures and obtain the quantitative velocity field. Streamlines and velocity contours analysis are used to identify specific flame structures and reveal the effect of steam added on the vortex structure. The results show both central fuel penetration limit and partially quenching limit in the humid air case reduce. The decrease in the critical penetration limit is primarily attributed to a reduction in momentum of the humid air. The flamelet concepts are applied to discuss the partially quenching limit in the blue neck region. The analysis reveals that the large decrease in the partially quenching limit is due to the increase in chemical reaction time of the humid air combustion.