The influence of high pressure on mass burning rates and flame height of ethanol square pool fires

The study of fire under high pressure is of great significance for the designing safety protection systems of submarines and underground space stations under high-pressure environment. To investigate the influence of high-pressure on mass burning rate and flame characteristics of square pool fires, three sizes square pools with the length of 2 cm, 4 cm, and 6 cm were carried under high pressure ranged from 1 to 3 atm, and mass burning rate and morphological characteristics of the flame were analyzed. Results showed that the mass burning rates gradually increased as pressure increased, which could be explained by different conduction thermal feedback affected by pressure. The mass burning rates of 4 cm- and 6 cm-length square pool fires were mainly dominated by conduction and convection heat feedback and were proportional to \({P}^{\text{n}}\), and the exponents were 0.25 and 0.32. But the change of 2 cm-length square pool fire was barely affected by the pressure. As the pressure increasing, the flame oscillation frequency was increased, and the shapes were transformed into relatively unstable because of the enhancement of buoyancy. The color of flame was found to be bright yellow totally owing to the incandescence of soot particles. Moreover, the flame height of 2 cm-length square pool fire increased with pressure increasing and could be expressed as \({h}_{\text{f}}/\dot{m}\propto {P}^{0.23}\), while the flame height of other pool fires decreased, which could be demonstrated as \({h}_{\text{f}}/{\dot{m}}^{2/5}\propto {P}^{-0.27}\) and \({h}_{\text{f}}/{\dot{m}}^{2/5}\propto {P}^{-0.35}\), respectively. Finally, Froude number and Strouhal number were used to characterize the flame pulsation frequency under high pressure. The method presented in this study can provide key scientific data and models to assess fire risk under high pressure.