Experimental and numerical study on flame morphology, plume flow and air entrainment of pool fire under the influence of the built-in obstacle

In the chemical industry park, leaking and burning liquid energy fuel may surround equipment such as unburned oil tanks, forming a fire scene under the influence of the built-in obstacle. A series of experiments and simulations were conducted to study the influence of the built-in obstacle with different sizes on flame morphology, plume flow and air entrainment for methanol and n-heptane. The results show that there are two horizontal high-speed zones under the influence of the high obstacle. One is caused by more fresh air need to be entrained quickly to maintain combustion. And the other is caused by upward developing vortices getting rid of the obstacle inhibition and promoting air entrainment. Then, through the force analysis of plume flow, the equivalent hydraulic diameter of pool fire in the existence of the obstacle was introduced, and the relationship between dimensionless flame height and dimensionless heat release rate was deduced. Furthermore, the influence of the obstacle size on air entrainment was quantitatively analyzed by introducing the relative air entrainment coefficient (α∗). Finally, through theoretical derivation, a prediction correlation of α∗ was established, which can well predict the asymptotic value of α∗ under the influence of the obstacle.