Influence of a Ceiling on Fire Plume Velocity and Temperature

A series of experiments with a fire impinging onto a ceiling were conducted to quantify the influence of a ceiling on the fire plume centerline gas temperatures and vertical velocities. A 0.3 m square porous burner with propane as the fuel type provided a steady-state diffusion flame. Time averaged gas temperatures and velocities were measured at 76 mm vertical intervals along the centerline of the impinging fire plume for fire heat release rates of 50 kW and 90 kW and flame height to ceiling height ratios of L _f /H = 2, 1.5, 1, and 0.8/0.85. At elevations close to the burner surface, gas temperature and velocity were independent of ceiling height. As the elevation above the burner increased, gas temperatures decreased slightly with increasing ceiling height, while velocities differed greatly across ceiling heights, initially increasing with elevation followed by a decrease toward zero close to the ceiling. Simulation results from fire dynamics simulator (FDS) compared well with measured gas temperature and velocity with their maximum values within 5.7% and 11.6%, respectively. Compared with fire plume correlations, gas temperatures compared well while velocities were in agreement up to 60% of the ceiling above which velocities decreased toward zero close to the ceiling.