Experimental study of the effect of delayed ignition on ethanol spill fire behavior on inclined surfaces

Different ignition time leads to different spread and prior evaporation processes of the leaked liquid fuels before being ignited. Under the coupling effect of the kinetic characteristics of the spread fuels in inclined substrates and the heat transfer mechanisms to the fuel layer from fire plumes, the spill fire behavior with different ignition time on inclined substrates in confined space is more complex. The relevant experimental tests and theoretical analysis can provide significant theoretical and technical support for the risk control of spill fire. Tests were conducted with ethanol at a spill rate of 39 ml/min on inclined steel trenches with different slopes of 0°, 1°, 3°, 5°, with instantaneous ignition and different delayed ignition time such as 10 s, 20 s, 30 s. Based on the thermocouple test data and MATLAB image processing, parameters such as burning area, spread rate, burning rate and flame height were analysed. The maximum burning area is increased with increasing delayed ignition time for spill fires on the same sloped substrate. The quasi-steady burning area is independent of the delayed ignition time, but increases with the increasing of the substrate slope. Considering the different absorption of the radiative heat feedback by the fuel layer in confined space, a modification is proposed in the existing burning rate model of spill fires. It was found that the spread rate of spill fire increases with increasing slope, which increases along with the increasing delayed ignition time on the substrate of the same slope. By integrating the effects of burning rate, burning radius, combustion heat of the fuel, and the inclination angle, etc., an equation for fitting the flame height is derived. It is found that the flame height in the quasi-steady burning phase decreases with increasing substrate slope and is independent of the delayed ignition time.