Experimental study of the effect of delayed ignition on the ethanol spill fire behaviour with different channel width in tunnel environment

Tanker trucks are susceptible to combustible liquid spill fire after an accident in the transport process. When the spill fire accident occurs in a road tunnel, the coupling of the kinetic properties of the diffused fuel and the heat transfer mechanism of the fire plume to the fuel layer is more complicated under the constraints of the tunnel environment, which can cause serious hazards to the surrounding environment. In this paper, instantaneous ignition and different delayed ignition time such as 10 s, 20 s, and 30 s were tested using ethanol at a spill rate of 78 ml/min on 10 cm, 15 cm, 20 cm, and 30 cm width steel channels in a model tunnel. Parameters such as burning area, spread rate and burning rate were analysed based on electronic balance data, thermocouple data and MATLAB image processing data. The findings show that an increase in substrate width and delayed ignition time results in an increase in the maximum burning area. The flame spread rate decreases with increasing substrate width at the same ignition time and increases with increasing delayed ignition time at the same width substrate. A spread rate prediction model was developed by analysing the forces on the fuel layer during the spread phase. A model for predicting the average burning rate during the spread phase was developed by taking into account the different absorption rates of radiant heat feedback by different fuel layer thicknesses during the spread phase in the tunnel space. A model for predicting the maximum burning area of delayed ignition ethanol spill fire on substrate of different width in tunnel was developed by combining the spread rate model and the burning rate model in the spreading phase. The results of this study are important reference for understanding the spreading and burning characteristics of spill fire accidents during road transport and the associated risk assessment.