Influence of stack effect on flame shapes of gas burner fires

Abstract

To study the influence of stack effect on air flow and flame shapes of gas burner fires, a set of experiments was conducted in a 1/3th scale building model. One 0.15m square porous gas burner with propane as fuel was used with 6 different HRRs (heat release rates) of 13.54, 27.08, 40.63, 54.17, 67.71 and 81.25kW. The window at different floors was opened respectively for different HRRs. Results show that the upper average smoke temperatures in the fire room are higher than that in the atria for the smaller HRR. With the increase of HRR, the upper average smoke temperatures in the fire room are lower than that in the atria. The heat pressure induced by smoke in the stairwell increases with the HRR and the height of opened window. The relationships between the non-dimensional air flow velocity, HRR and height from fire source to the centerline of opened window are put forward based on the experimental results. The non-dimensional mean flame length is also proportional to the 2/5 power of non-dimensional HRR, but shows smaller than the Heskestad’s equation. For the propane porous gas burner, whose HRR is independent of the heat feedback to the burner surface, the average flame tilt angle increases with HRR, but the increment becomes relatively small for the larger HRR.