Experimental study on flame height and heat release rate estimation of diesel-wetted wood powder fire

Abstract

This paper experimentally studied the temperature profile and flame height variation of diesel-wetted wood powder fire. Fuel component ratio (the mass ratio of diesel to wood powder) and burner diameter were considered. Results show that due to difference of flash/ignition point between diesel and wood powder, main combustion component changes gradually from diesel to wood powder. Hence, the axial temperature rises sharply first and then decreases gradually. According to axial temperature, combustion is generally divided into three stages: (1) rapid burning, (2) transition and (3) steady burning. In rapid burning stage, lateral temperature profile conforms to Yokoi profile above the flame height and to ‘Top-hat’ profile below the flame height. Heat release rate (HRR) is estimated using axial temperature profile based on McCaffrey's model. HRR of this kind of fire is much lower than that of pool fire with the same burner size. Due to decrease of fuel feed rate, flame height decreases constantly and was correlated with mass loss rate per unit area. Flame transits into ‘mass fire’ when dimensionless flame height decrease to about 0.3. The work is expected to help evaluate the thermal hazard and facilitate the detection of this kind of fire.