An experimental study on the heating and burning of a binary liquid mixture in a pool fire

Abstract

The paper presents an experimental study on the transient heating and burning of binary mixtures of cyclohexane and methanol in square burners made of steel and with three different side lengths: 8.0, 10.5 and 15.0 cm. Each burner is 5 cm deep, and the initial fuel height is about 4.6–4.8 cm. Experimental measurements of the transient profiles of burning rates and liquid temperatures (at different depths below the surface) are carried out. Prior to ignition, an upper cyclohexane-rich layer settles above a lower methanol-rich layer. During the initial transient and steady-state periods, the burning is slightly lower than that of pure cyclohexane due to the presence of methanol in the upper layer. Then, the expansion of methanol vapor – forming at the interface between the two layers and reaching the surface – causes the phenomenon of boilover, which is characterized in terms of onset time, peak intensity and duration for different initial mixture compositions. After boilover, depending on the initial amount of methanol, there could be either (i) burning of (almost) pure cyclohexane, (ii) azeotropic burning, or (iii) azeotropic burning followed by the burning of (almost) pure cyclohexane. These results provide more insights into phenomena that are relevant to practical applications in fire safety or industrial fire hazard management, such as tank fires.