ELEMENTARY REACTION MODELS AND CORRELATIONS FOR BURNING VELOCITIES OFMULTICOMPONENT ORGANIC FUEL MIXTURES

This computational study uses elementary reaction mechanisms to interp ret the trends in a database of burning velocities for multicomponent organic fuel mixtures derived from coal. These mixtures contain CO, H- 2, CH4, C2H2, oils, and, in some cases, appreciable amounts of C2H4, C 2H6, C3H6, and C3H8 The database represents fuel equivalence ratios fr om 0.5 to 1.5, two unburned gas temperatures, and two diluent: O-2 rat ios. Predicted burning velocities are based on a one-dimensional lamin ar flame code with the Miller-Bowman mechanism without nitrogen conver sion chemistry or oxidative pyrolysis of any higher hydrocarbons. The initial amounts of oils and higher hydrocarbons are expressed as addit ional amounts of C2H4 and C2H6 and reduced levels of H-2. Burning velo cities of multicomponent fuel mixtures at high temperatures can be int erpreted with only oxyhydrogen and C-1/C-2 chemistry without any fuel decomposition steps for the higher hydrocarbons. This approach rationa lizes the trends due to higher extents of secondary volatiles pyrolysi s, which means increasing CO and H-2 levels and diminishing hydrocarbo n Levels in the fuel mixtures. It also rationalizes the variations wit h coals of higher rank, which means diminishing CO levels and H-2 and hydrocarbon levels that pass through maxima. Predictions from the elem entary reaction mechanism are quantiatively accurate for nearly all le an mixtures, but discrepancies are substantial for rich mixtures, espe cially those with abundant CO and H-2. Systematic overpredictions for rich mixtures are probably due to defects in steps for the attack of C -1 or C-2 species by O-2 or H atoms.