Experimental and numerical study on the occurrence of off-stagnation peak in heat flux for laminar methane/air flame impinging on a flat surface

A combined experimental and numerical study has been conducted to investigate the occurrence of off-stagnation peak for laminar methane/air flame impinging on a flat surface. Experiments were conducted for three tube burners of internal diameter 8 mm, 9.7 mm and 12 mm. Radial heat flux distributions were compared (experimentally) for different burner diameters under identical operating conditions (with firing rates of 0.25 kW, 0.40 kW and 0.50 kW, ϕ = 1 and H = 40 mm). An off-stagnation point peak in heat flux was observed for some of the configurations in the present study which is in accordance with the previous findings. This off-stagnation point peak is a function of stand-off distance between the exit plane of the burner and the plate and also the distance between flame-tip and the plate. A satisfactory explanation is presented to explain the existence of this off-stagnation peak with the help of results of numerical simulation carried out with commercial CFD code FLUENT. It is concluded that this off-stagnation peak in heat flux is primarily due to the peak in the axial velocity profile close to the impingement surface.