Abstract:

To analyze the spread characteristics of spill fires in narrow and confined spaces, a reduced-scale tunnel model with dimensions of 6 m × 1 m × 1 m was established, and a series of spill fire tests were conducted under six different leakage rates using methanol as the fuel. Characteristic parameters, including diffusion diameter, flame shape, flame height, flame temperature and radiative heat flux, were analyzed to explore the influence of leakage rate on spill fire spread behavior in narrow and confined spaces. The results show that the spread process of methanol spill fires can be divided into four stages: diffusive combustion, contraction, quasi-steady combustion and extinction. In the quasi-steady combustion stage, the flame shape is dominated by a trapezoid at low leakage rates (50-100 mL/min), while the flame presents a triangular shape with a prominent bifurcation phenomenon at high leakage rates (150-250 mL/min). Both the mass burning rate and flame radiative heat flux of methanol spill fires increase with leakage rate, and their growth rates show a decreasing trend, the mass burning rate of methanol spill fires is approximately 2/5 to 2/3 of that of methanol pool fires at the same scale. The dimensionless flame temperature remains stable within the range of dimensionless height characteristic values of [0.09,0.41), decreases significantly within [0.41,1.03), and declines more rapidly within [1.03,2.49].

Key words: narrow and confined space, continuous-leakage, methanol spill fire, leakage rate, mass burning rate, radiative heat flux