Numerical modelling of liquid fuel fire whirl

This work presents the numerical modelling of a fire whirl generated from the liquid fuel. Fire Dynamics Simulator (FDS) was used as a CFD tool to simulate a fire whirl under predefined boundary conditions. A pyrolysis model is utilized to model the evaporation of liquid fuel. Numerical results of the Mass Burning Rate (MBR), flame height (Hf), temperature profiles, velocity contours, and velocity profiles are described. The comparison between a fire whirl (hot flow) and an air whirl (cold flow) reveals an up to 40% increase in the centreline axial velocity due to the buoyancy generated from fires. The predicted MBR and flame height agreed with the experimental data, with an uncertainty of ±14% and ±11%, respectively. It was found that the swirling flame exhibits a higher length and more concentrated regions of Heat Release Rate (HRR) than the non-swirling flame. They contribute to enhanced combustion, higher HRR, faster flame propagation, turbulence enhancement, complex flow patterns, and potential flame instabilities. The evolution of the fire whirl was studied using velocity vectors across the fire whirl, and precise tangential and axial velocity profiles were predicted through numerical analysis. The measured and predicted flow fields were found to be in agreement. The study shows that FDS is an efficient and capable CFD tool for studying various aspects of fire whirls.