Investigation of Stability Limits of a Premixed Counter Flame
In combustion operations, flame fronts are often spread in an irregular. Therefore, the temperature and flame speed varies along the flame's front and depend on the asymmetry of the composition of the mixture and the conditions of the local flow before the flame, especially this behavior is evident in double counter flames. This paper describes an analytical study of stability limits of premixed counter flame. The investigation is based on experiments carried out to identify the effect of varying the distance between upper and lower burner edges on the stability limits at different equivalence ratio values; liquid petroleum gas (LPG) was used as fuel in experiments. The blow-off limit, disc flame limit, and double flame limit were investigated. Under the change of fuel gas-air flow velocity, in this type of flames, the conical flame is transformed into mushroom-shaped tented flame attached to the widened convex apex in the medial distance between the upper and lower burner edges. The experimental data and numerical analysis obtained show that high-stability for double flame, fuel-rich premixed flame operate over narrow range of equivalence ratio φ from 0.43 to 1.41. The ANSYS 17.0 FLUENT Premixed Flamelet Module with pre-processing was used. The results appear that increasing distance between burner edges decreases the flame stability efficiency.