Flame attachment effect on the distributions of flow, temperature and heat flux of inclined fire plume

Abstract

The flame attachment behaviors over an inclined surface were investigated by a gas burner, and its effects on the temperature, heat flux, and the velocity distribution were explored by the heat flux meter, infrared thermography and particle image velocimetry (PIV) systems. The results showed that a sudden increase in flame attachment length occurred when the inclination angle of the surface increased from 15 to 20o, which caused the sharp increase of the temperature, the heat flux as well as the flame spread parameter ψ. Combined with PIV, it was found that a large velocity difference appeared between the upstream and downstream of the flame when the inclination angle increased from 15 to 20o. The vortexes induced by the velocity difference moved upward periodically along the edge of the flame, increased the turbulence intensity and accelerated flame attachment greatly. By introducing the local Richardson number (Rix) and the dimensionless local total heat flux, it was found that the plume was dominated by the momentum near the burner while dominated by the buoyancy in the distance. The turning point of the two regimes occurred at the ratio between the flame length to the burner hydraulic diameter of 0.5 and Rix ≈10, and the local heat flux distribution of downstream fire was further obtained.