Fire Safety Science Digital Archive

This work attempts to develop a quantitative understanding of the chemical and physical gas Phase fire suppression mechanisms of water. Small-scale diffusion flame experiments and calculations with detailed kinetics are done to study these gas-phase effects. The experimental results show that there is a significant chemical enhancement effect due to increased water vapor concentration in the flame zone. This effect reduces the soot concentration and oxidizes CO to CO,. Consequently, the combustion becomes more complete and the flame temperature is increased as the water concentration is increased. The actual magnitude of the chemical enhancement, however, depends on the water concentration, the 0, concentration and the flame temperature. Mixing caused by liquid water application and water evaporation may significantly affect the gas composition. In particular it may increase the CO concentration for a low 0, concentration fire environment. It was also found that an increase in the water vapor concentration considerably enhances the radiative heat loss from the flame. This heat loss becomes less significant with increase in the strain rate due to a reduction in the flame zone thickness