AN EXPERIMENTAL AND NUMERICAL STUDY OF VOLATILE COMBUSTION OF SINGLE COAL PARTICLES IN AN OXYGEN ENRICHED ATMOSPHERE

摘要

The aim of this work is to experimentally investigate the effects of devolatilization after particles have crossed a laminar flame front and to compare the findings with results obtained by a Large Eddy Simulation (LES) modeling strategy based upon tabulated chemistry of volatiles combustion. For this purpose a flat flame burner was designed to provide oxygen enriched CO_2 and N2 environments at elevated temperatures for fundamental studies of the devolatilization, ignition, and volatile combustion processes of single coal particles. In this work one type of coal with different particle size ranges has been investigated in a hot atmosphere of N2 and O_2 downstream of the flat flame front. High-speed laser induced fluorescence of OH at 10 kHz was used to address ignition and the burning of the volatiles.rnA LES has been performed to capture the transient behavior of volatile combustion around single particles. For this, the academic three-dimensional finite volume code FASTEST has been used. The two-phase flow was computed by an Euler-Lagrange approach. The Flamelet Generated Manifolds (FGM) concept has been coupled with a coal devolatilization model. In this approach, the detailed chemical reaction processes were computed prior to the actual CFD simulation and then mapped onto a manifold which was spanned by a reduced set of control variables. These are the mixture fraction, a reaction progress variable, and the enthalpy. To account for devolatilizing gases, source terms have been included in the corresponding transport equations. Numerical data of the reacting particles and the laminar flame are compared with experimental measurements with respect to the onset of volatile combustion.