Experimental study on n-heptane pool fire behavior under dynamic pressure in an altitude chamber

Abstract

The objective of this work is to examine the effect of dynamic pressure on the behavior of a horizontally burning flame based on experimental approach. The experiments were conducted in a large-scale altitude chamber of size 2 m × 3 m × 4.65 m under three different dynamic pressures with various depressurization rates. Two round steel fuel pans of 20 or 30 cm in diameter were chosen for the pool fire tests. The fuel pan was filled with 99% pure liquid n-heptane. Cold water was added beneath the fuel layer to cool the pan and minimize the temperature rise in the fuel. The experimental result that the average burning rate for the 30-cm-diameter pan is approximately triple to that for the 20-cm-diameter pan implies the significant influence of pan size on mass burning rate, while the depressurization rate shows minor influence on the mass burning rate. Mass burning rate \(\dot{m}\) during quasi-steady burning stage increases with pressure P as a power exponent function \(P^{\alpha }\), and the power exponent factor α increases with the pool size and is lower under higher depressurization rate. The peak radiative heat flux in 30-cm-diameter cases is approximately 1.5 times higher than that in 20-cm-diameter cases. But there is little impact on the peak radiative heat flux from the depressurization rate. Additionally, the flame temperature at the flame root in 20-cm-diameter pan fire tests is more stable and higher than that in 30-cm-diameter pan fire tests. But at flame front, the flame temperature in 20-cm-diameter pan fire tests falls rapidly and is apparently lower than that in the 30-cm-diameter pan fire tests.