Modelling and effects of fuel radiation in methanol pool fires

Abstract

This article proposes a computationally affordable radiative heat transfer model to predict accurately the feedback toward the fuel surface. It combines the multi-scale full-spectrum k (MSFSK) approach to model accurately the radiative interaction between CO2/H2O and the fuel and the rank correlated (RCFSK) scheme. The model achieves the narrow band correlated-k model accuracy with only five quadrature points for each of the two scales. The predictions are also weakly dependent on the Planck temperature which allows to store efficiently the MSRCFSK parameters in a flamelet library. The model is implemented in a well-validated numerical model to provide large eddy simulations of 30 cm and 1 m diameter methanol pool fires. The heat feedback predictions are improved when methanol radiation is considered. The overall radiative contribution of methanol results from two competitive mechanisms: an increase in emission in the hot part of the fuel dome and an increase in absorption close to the pool surface. For both pool fires, the enhancement in emission overall dominates, leading to higher radiative loss and heat feedback. The contribution of absorption increases with the pool size and, as a result, the effects of methanol radiation are more pronounced for the 30 cm pool than for the 1 m one.