CFD modelling of confined jet fires under ventilation-controlled conditions

Abstract

This paper presents field predictions for two confined jet fires under ventilation-controlled conditions. Three different combustion models, namely the laminar flamelet model, the constrained equilibrium (CE) method and the eddy break-up (EBU) model, are used and compared. The laminar flamelet model and the CE method are coupled with Lindstedt's soot model, while the EDU model is coupled with the soot model of Magnussen. The global radiative heat exchange is considered by using the discrete transfer radiation method (DTRM) and the calculation of the microscopic radiative heat exchange within the flamelet is embeded in RUN-1DL. For both the flamelet and CE methods, the energy equation is solved so that the radiation calculation is coupled with the computation of the turbulent combustion processes. Comparisons are made between the experimental data and the predictions of different sub-model combinations for two propane jet fires in enclosures of 135 and 415 m 3. It is found that all the sub-model combinations predict the correct trends of distributions for field variables such as velocity, temperature, soot, and CO. The predicted temperature distributions from the flamelet approach, which includes both the microscopic and global radiative heat losses, are found to be in close agreement with the experimental data. Modifications are made to the convective heat transfer coefficients between the wall and the gaseous products in the impinging region and this is found to have improved the predictions for the wall heat fluxes.