Influence of gas–liquid ratio on the fire-extinguishing efficiency of compressed gas protein foam in diesel pool fire

The fire-extinguishing efficiency of compressed gas protein foam with different gas–liquid ratio on diesel pool fire was studied by a laboratory-scale fire suppression experiment. The 25% drainage time, expansion ratio and fire-extinguishing efficiency of 6% protein foams (PF) with the gas–liquid ratio in the range of 5–24 were tested. The results show that as gas–liquid ratio increases, both the 25% drainage time and expansion ratio increase. In the fire-extinguishing process, the temperature drop rate increases at the beginning and then decreases with the increase of gas–liquid ratio. When the gas–liquid ratio is 20, the foam shows the optimal equilibrium between the fluidity and stability, thus exerting the maximum temperature drop rate of 6.86 K s −1 corresponding to the best fire-extinguishing efficiency. The main fire-extinguishing mechanism of PF in pool fire is ascribed to the combined actions of cooling effect and barrier effect. By adjusting the gas–liquid ratio in the range of 16–24, the PF can exert excellent fire-extinguishing efficiency in pool fire by diluting the combustible gases and isolating the transmission of heat and oxygen between combustion zone and fuel.