Heat release rate prediction for high-altitude gasoline pool fires based on field tests of combustion characteristics

Abstract

The heat release rate is of great significance for fire protection design, whether in highway tunnel, building, oil depot and aircraft. Simply, the heat release rate can be estimated by multiplying the mass loss rate by the effective heat of combustion, which can be investigated via pool fire test, because of its wide applicability in various fire scenarios. In fact, both mass loss rate and effective heat of combustion are affected by the high-altitude environment, including the low atmospheric pressure and low ambient temperature. Thus, to obtain the mass loss rate and effective heat of combustion, field tests of gasoline pool fire were conducted at 4 altitudes. The test environments of 4 altitudes were consistent with that of real fires at high altitudes, especially the atmospheric pressure and ambient temperature, to ensure that the measuring data were correct. The heat release rate at high altitudes were calculated by using the fitting formulas of mass loss rate and effective heat of combustion, which were presented in this paper. The results revealed the following: (1) Both the atmospheric pressure and ambient temperature were important factors for the mass loss rate and effective heat of combustion. (2) Based on a global model and flame temperature correlation, a mass loss rate estimation method was established. After analysis, a linear relationship between lnm˙ and lnP∞ was identified for temperature greater than 0 °C, otherwise, there was a logarithmic relationship between lnm˙ and lnP∞. In addition, the fitting formula of mass loss rate was obtained. (3) A theoretical method of effective heat of combustion based on the Gibbs energy minimization approach was established. For simplification, the effects of atmospheric pressure and ambient temperature were approximately independent. The effective heat of combustion increased linearly with both atmospheric pressure and ambient temperature, and the fitting formula was gained by considering above two factors. (4) The heat release rates of gasoline pool fire at high altitudes were calculated, which varied with ambient temperature as the Gaussian function. And the relationship between heat release rate and atmospheric pressure was power function. The atmospheric pressure effect on heat release rate was more significant at temperatures lower than 10 °C. The results in this work could provide a basis for heat release rate prediction studies and subsequent research on smoke diffusion, whether in aircraft, highway tunnel, building and oil depot at high altitudes.