Experimental prediction on the performance and propagation of ceiling jets under the influence of wall confinement

Characteristics of ceiling jets propagation are very significant for energy detecting and controlling once an undesirable energy source releasing flame and toxic pollutant emissions is erupted in a building. In many cases, the impinging ceiling jet flame will be affected by the nearby wall, especially for the energy source very close to or immediately against a wall. Four sets of experiments were conducted with energy source in open space, confined by an unbounded ceiling, confined by a wall-ceiling configuration and confined by two parallel walls (a corridor-like structure). Results show that the impinging ceiling jet-flame behaves very differently in different wall-ceiling configurations, the ceiling flame extension and the heat flux to nearby field increases dramatically with increasing confinement strength, from unbounded ceiling to narrow confined corridor-like structure. Based on the limits of flame extension, the temperature distribution under the ceiling can be divided into the near-field region within the ceiling flame and the far-field region beyond the ceiling flame. Predictive correlations of ceiling flame and temperature distribution are proposed to account for different wall-ceiling configurations. The results of this study have implications to optimize the design and arrangement of the ceiling-mounted heat and energy detection, protection and controlling systems.