Flame Blowoff Studies Using Large-Scale Flameholders

Abstract

Experimental and theoretical studies are made of the factors governing the blowoff velocities of stabilized flames supplied with flowing gaseous combustible mixtures. The test program includes wide variations in effective pressure, obtained using the water injection technique, and also covers wide ranges of velocity, flameholder size, and flameholder blockage. An equation is derived for predicting blowoff velocities which shows good agreement with the experimental data.

Lean blowoff of bluff body stabilized flames: Scaling and dynamics

“…These include bluff body width, boundary layer thickness, Taylor micro or macroscales, width of the wake, and time averaged recirculation zone length. As pointed out by Rao and Lefebvre [90], these scalings are all proportional to the geometric width of the bluff body and will often lead to similar conclusions. Boundary layer momentum thickness scaling was determined using the relationship:…”

A Model for Bluff Body Flame Stabilization

“…F(g) = C g (1 -B de ) D Although most parameters are defined in the nomenclature, C g and BHe need to be calculated from an expression given [22] and the parameters E', a and AT, which have been experimentally determined, can be evaluated from given values of T o and [12,15]. The agreement between measured and calculated values is quite good (Fig.…”

“…In fact, the operating conditions in afterburners at high altitude can vary from one regime to the other. Current modelling of afterburner combustion states that blow off occurs when chemical time is equal to residence time with the restriction that it should apply to a a turbulent regime only [1,6,22]. The point is, even if the approaching gas is in a laminar regime, because of the blockage effect, the flow will remain in a turbulent regime in the shear layer: otherwise mixing will be insufficient and blow off would occur.…”

Performance Characteristics of Controllable Flat-Plate Flameholders

“…However, a significant reduction in the weight of the flameholder could be achieved. Rao and Lefebvre (1982) further showed the better stabilizing characteristics of the single vortex flow pattern (the so-called single-sided flameholder) compared to the conventional V-gutter type flameholder. However, Rizk and Lefebvre (1986) found that the improved stability performance of the single-sided flameholder was subject to the sacrifice of a higher drag coefficient.…”