Investigation of Stability Limits of a Premixed Counter Flame

The urgent need to improve premixed combustion processes in industrial furnaces and boilers is a major challenge; to power-increasing and reduces emissions. Many studies investigated the flame structure influences from the local extinctions perspective for different fuels. But, the stability limits for a premixed counter flame haven't been widely studied. In combustion operations, flame fronts are often spread in an irregular way. Therefore, the flame speed and temperature vary alongside the front of flame and rely upon the mixture composition asymmetry and the conditions of the local flow before the flame; especially this behaviour is evident in the double counter flames. The present research describes an analytical study of the stability limits of a premixed counter flame. This study is founded on experiments performed to identify the influence of changing the distance between the 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. The laminar counter flame model by using ANSYS 17.0 Premixed Flamelet Model (PFM) was used for simulating the counter flame of LPG and air mixture, under the influence of the distance between the burner edges. The outcomes experimental data were compared with the numerical and a good agreement was obtained. The experimental data and numerical analysis obtained manifested that the high stability for double flame, fuel-rich premixed flame operate over a narrow range of equivalence ratio (phi) from 0.43 to 1.41. The results elucidated that increasing the distance between the burner edges decreases the flame stability efficiency.