3-D Simulation of Ignition in the Head Vortex of a Reactive Hot Jet Injected into Flammable Mixture

A practical way to ignite a flammable mixture is the use of a sudden jet or puff of hot combustion product of a pre-chamber that is injected into a relatively cold reactive mixture of fuel and air. Rapid mixing of hot reactive gas with fuel and air can allow ignition at distributed ignition sites. Two primary regions comprise the puff, the near-field region, which consists of the high velocity trailing jet, and the head-vortex ring in the far-field region which is the main objective of this research. The leading vortex's entrainment process is presumed to occur by engulfing the surrounding gases and then undergoing a slow diffusion of mass. The ignition process is significantly different in these two regions due to the considerably distinct mixing processes. Given universal vortex behaviors, empirical correlations are to be used to characterize the vortex ring's initiation, development, and separation. In the present study, the large-eddy simulation (LES) is employed to study the composition and ignition of the head vortex ring for CH4-H2-Air mixture with varied fuel reactivity blends and equivalence ratios. The computational domain is comprised of a circular orifice with D = 6 mm coupling to an enclosure with side and length ratios of W/D = 4, and L/D = 5, respectively. The turbulent hot jet is issued with the velocity of Uj = 360 m/s in adiabatic flame temperature with various compositions.