Analysis of the Roll-Paper Fire Plume with Application to Suppression

摘要

To enable an increased understanding of fire suppression phenomena for roll-paper storages, fires with convective heat release rates (HRR) of 14-44 MW on a roll-paper array stored under a ceiling were simulated in the presence of automatic sprinkler sprays. Plume strength was identified as a key parameter controlling the suppression effectiveness of sprays. The plume strength was defined as the peak integrated plume thrust force above the array, in a region where the primary interaction between spray and plume occurs. For the specific scenario investigated, the plume strength found for convective HRR beyond 27 MW asymptotes due to excess unburnt fuel not contributing to the plume vertical thrust force and, rather, burning in the ceiling jet. Spray-plume interaction simulations were conducted for this range of convective HRRs. For the selected sprinkler water flow rate, the plume momentum is affected considerably for the lower HRRs. For the higher HRR, the downward spray momentum is overcome by the plume momentum, with the majority of the momentum exchange between the spray and plume occuring close to the ceiling. A height was identified where the spray and plume thrust forces are balanced. If this location is close to the ceiling (meaning the spray is overpowered by the plume), the time-averaged ceiling jet temperatures are greater than sprinkler activation temperatures at significant distances from the plume impingement region.