Experimental Investigation on the Variation in Solid Fuel Fire Whirl Properties with Imposed and Fuel Rotation

This work presents a study on the formation of laboratory- scale fire whirls using forest fuels to replicate real-world fire whirls. A total of 48 experiments are conducted using three distinct types of forest fuels, namely Pinus Roxburghii, Shorea Robusta, and Grevillea Robusta, with three fuel pans of diameter 0.2 m, 0.3 m, and 0.4 m, respectively. Different characteristics such as Mass Burning Rate (MBR), Heat Release Rate (HRR), flame height, flame temperature, radiative heat flux and fire effluents are measured for a range of HRRs 40-346 kW and correlations are developed in terms of circulation and diameter. In comparison to free burning, the HRR was found to be increased by 300% with imposed rotation which was further increased up to 65% with fuel rotation. The flame heights are  also increased by 30% in the case of imposed rotation and 40% with both imposed and fuel rotation. A detailed measurement of fire effluents revealed that their concentrations for fire whirls were reduced in the range of 50% to 400% compared to free burning fires. Furthermore, the developed correlations were applied to fire whirls of HRRs (up to ∼ 1900 kW) and their validity in predicting the characteristics was ensured.