Numerical simulation of combustion in fire plumes

Abstract

Combustion in buoyancy-driven fire plumes is assumed to be diffusion controlled and described by a mixture fraction variable. Experimental data for a 10-cm methanol pool fire was compared to numerical results obtained by assuming the plume was axially symmetric. No turbulence model was used. The influence of imposing axial symmetry independent of the approximations made in the combustion model was tested by comparing simulated and experimental helium plumes. Simulated helium plume results agreed well with the experimental data at sufficiently small heights where most combustion occurs. At larger heights, predictions from the helium simulations were increasingly in error within a volume surrounding the centerline. Prediction error in the pool fire simulations behaved largely in a similar manner, with some error present due to inadequacies in the mixture-fraction-based combustion model. Overall, within the limitations of an axially-symmetric calculation, the behavior of flame flickering and the time-averaged temperature field were reasonably well predicted.