Numerical investigation on flame propagation characteristics of non-premixed hydrogen and air in a curved micro-combustor

Abstract

In the present study, propagation characteristics of non-premixed H2/air flames in a curved micro-combustor were numerically investigated. Five distinct flame propagation modes were identified, including the stable flames behind the separating plate and oscillating flames in the curved channel. Analysis showed that the flame sloping direction was determined by local distributions of both equivalence ratio and velocity. In addition, tip opening and tip intensified phenomena of V-shaped flames are attributed to the Lewis number effect. Flame splitting phenomenon occurs when ϕ ≤ 1.0, which is a result of the stretch effect. Moreover, the flame propagation time (i.e., the duration for the flame to reach the separating plate) first decreases and then increases with the increase of nominal equivalence ratio, and the shortest value appears at ϕ = 1.6 and 1.7. Furthermore, the flame propagation limit (i.e., maximum propagable velocity) varies non-monotonically with nominal equivalence ratio, and the peak value is obtained at ϕ = 1.3. In conclusion, the present study revealed more details of the propagation processes for non-premixed H2/air flames which cannot be fully detected through experiments.