Experimental investigation on the stabilization mechanism of jet diffusion flames

Large eddy simulation of spark ignition in a turbulent methane jet

“…29) so that the flame sensor S (constructed as a reaction rate) is not activated in this zone. This shows that mixing is not affected by the combustion model upstream of the flame front, a necessary condition to capture the stabilization processes [82,83]. Figure 30 presents the values of the thickening factor F and of the efficiency function E (cf.…”

Effects of fuel cetane number on the structure of diesel spray combustion: An accelerated Eulerian stochastic fields method

“…These mechanisms are: (1) fuel and oxidizer are premixed within the liftoff height such that the base of a lifted flame burns as a turbulent premixed-flame [1], which implies that a lifted flame is stabilized where the turbulent flame speed is balanced by the incoming reactant velocity [2]; (2) fuel and oxidizer remain non-premixed within the liftoff height such that the base of a lifted-flame burns as a diffusion-flame [3], which implies that a lifted-flame is stabilized at the location where the local scalar dissipation rate is equal to the critical dissipation rate at extinction; and (3) fuel and oxidizer are partially premixed within the liftoff height such that a lifted-flame at its base burns as an edge-flame [4] which is made up of a lean premixed branch, a rich premixed branch and a diffusion flame (the so-called triple-flame) that intersect at the triple-point. The main difference between propagation of an edge-flame and that of a stoichiometric premixed-flame is that the incoming reactant stream diverges significantly due to the heat release from the edge-flame; therefore, the effective flame-front-normal component of the incoming velocity at the base of an edge-flame is smaller than that of the main stream velocity further upstream in the flow [5].…”

Nonpremixed Flamelet Statistics at Flame Base of Lifted Turbulent Jet Nonpremixed Flames

“…Pitts (3) reviewed important theories proposed in terms of the flame stabilization mechanism. The problem of whether flame stability is determined by flame stretch (4) or the balance between premixed turbulent burning velocity and average flow velocity (5), (6) remains unclear. Recent laser measurements may have revealed the existence of each triple flame, consisting of a nonpremixed flame, a rich premixed flame, and a lean premixed flame at the bases of lifted tur-bulent nonpremixed flames (7) - (9) , providing evidence that lifted turbulent nonpremixed flames have the characteristics of premixed combustion, such as flame propagation at the flame base.…”