Heat Transfer Characteristics of Methane–Air-Premixed Jet Flames With Flat/Hemispherical Walls

Abstract

The in-depth study of the mutual coupling between the flame and the wall can significantly enhance the efficiency of actual combustion devices. A two-dimensional numerical model of the heat transfer characteristics of methane-air premixed jet flames with flat/hemispherical walls has been developed. An examination of the effects of wall shape on the heat transfer characteristics of methane/air flames was conducted as a function of the equivalence ratio (ϕ=0.9-1.5), the mixture Reynolds number (Re=300-800), and the burner-to-plate distance (H/d=1-6). As the equivalence ratio and Reynolds number increase, the flame temperature increases on the surface near the wall, and the temperature near the flame centerline is higher under the influence of a hemispherical wall than it is under the influence of a plate. In addition, the wall's heat flux increases as both the equivalence ratio and the Reynolds number increase. It is observed that the heat flux of the hemispherical wall is greater than that of the flat plate near the stagnation point, whereas it is smaller at a distance from the stagnation point. Due to the burner-to-plate distance, thermal efficiency is maximized when the flame premixed cone contacts the impact surface, which is the desired condition for optimal performance. Due to different operating conditions, the efficiency of heat transfer is always higher under the action of a flat plate than under the action of a hemispherical wall.