Investigating the Performance of Smoke Cooling during Compartment Firefighting

Compartment firefighting introduces various unique hazards. Many of these hazards relate to the smoke layer and the fuel contained within it. A method to manage the smoke layer is to pulse water into this layer to generate steam and absorb thermal energy, thereby significantly reducing the likelihood of ignition of the volatile gaseous within the smoke layer. This technique is referred to as “smoke cooling”. The development of smoke cooling techniques has been primarily driven by operators. There has not been an in-depth parametric analysis of the effects of the discharged water droplets upon the thermal response of the smoke layer. The research described in this thesis addresses this knowledge gap by investigating factors influencing smoke cooling performance. The analyses highlight 10 critical droplet parameters that determine whether smoke cooling occurs. These are: • flow from the discharge (l); • average discharge angle (°); • average discharge velocity (m/s); • DV,10 (microns); • DV,50 (microns); • DV,90 (microns); • relaxation time, DV,90 (s); • stokes number, DV,90; • group momentum (kg.m/s); and • group kinetic energy (J). Five fire scenarios were used based on five different fuel sources. Droplet parameters were generated for 78 different nozzle configurations where each configuration is defined as a specific nozzle at a specific pressure. These nozzle configurations were then discharged in three different smoke cooling techniques based on the angle of attack, plus a continuous Fig-8 discharge technique. Overall, around 2700 tests where undertaken. Besides significant experimental work, several of the test scenarios were numerically modelled using the Fire Dynamic Simulator software and the results compared to the physical tests to ascertain its ability to model the complex processes involved in smoke cooling. Overall, the novel smoke cooling operational envelopes developed in this thesis can be used to select suitable hand-held nozzles, over a range of pressures, to support smoke cooling within a compartment fire. Such critical information will provide firefighters with significant tactical guidance to ensure effective application of this technique, thereby allowing firefighters to not only quickly advance towards the seat of the fire to extinguish it, but also conduct victim searches with reduced risk to their own safety