Effect of scale and fuel type on the characteristics of pool fires for fire fighting training

This paper examines the effects of pool size and fuel type on the characteristics of pool fires. The fuels studied include hydrocarbon solvents, alcohol and their blends. The large-scale experiments were conducted on 0.445 and 1 m diameter pools in two enclosures: 41 m long×5.4 m wide×2.4 m high and 25 m long×2.7 m wide×2.4 m high, under a ventilation rate of 1–1.2 m/s. In these tests, measurements of the fuel pyrolysis mass loss rate, heat release rate (from CO₂ and CO concentrations as well as oxygen depletion), smoke extinction area (from laser attenuation), total heat flux emanating from the flame, and the yields of CO₂ and CO were made. Bench-scale tests were conducted using the same fuels and fuel blends on 100 mm× 100 mm pool fires in a Cone Calorimeter—a well-known fire test method.

The hydrocarbon+alcohol fuel blends are used to create large pool fires for fire fighting training. The aim of this study was to: (1) Formulate a fuel blend which will produce a “hot” fire for realistic fire fighting training while generating a minimal quantity of smoke to comply with the pollution regulations. (2) Investigate the effect of fuel type and scale on the properties of the pool fires. (3) Make comprehensive measurements on pool fires in tunnels which can be used for validating mathematical fire models.

This study has resulted in the formulation of a fuel blend which satisfies the requirements of fire fighting training as well as Environment Protection Authority of New South Wales. The bench and the large-scale results correlate well showing good agreement between the heat of combustion, smoke extinction area (SEA) and the yields of CO₂ and CO. The SEA increases with the CO and CO₂ yields which in turn increase with the carbon fraction and the aromatic content of the fuel/fuel blend. The SEA correlates strongly with the CO and CO₂ yields and in both the correlations, the entire data collapse on a single curve. These correlations indicate that the SEA and the CO₂ and CO yields vary mainly with the fuel type, and not so much with the pool size. The flame heat flux increases with the carbon content in the fuel.