Geometric characteristics and radiative heat flux at the downstream centerline and lateral ground for propane and methane diffusion flames under strong wind environments

Abstract

The geometric characteristics and radiative heat flux delivered to the downstream centerline and lateral ground for diffusion flames under wind environments were investigated in the present study. A series of combustion experiments were conducted with a 0.1m square gas burner, using propane and methane as fuel. Under the coupling effect of wind momentum and buoyancy, flame base drag length ($L_{drag}$) and inclination angle ($\theta$) show an opposite trend with increasing wind velocity. In addition, a considerable difference exists between the geometric characteristics of propane and methane flames. Using the specific upward acceleration derived from the centerline trajectories of propane and methane flames, unified correlations to predict the geometric parameters of propane and methane flames were proposed. The radiative heat flux at the downstream centerline and lateral ground peaks at a downstream location ($x$) close to the trailing edge of the flame base drag. The effect of wind velocity and fuel flow rate on the flame radiation at the downstream centerline stems from changes in local flame emissivity. Flame radiation delivered to the lateral ground at $x>L_{drag}$ increases with wind velocity due to the increased view factor. At $x<L_{drag}$, the effect of wind velocity on the flame radiation depends on the fuel flow rate. Based on a simplified flame model, the radiative heat flux at different positions was reasonably predicted.