Correlations for the laminar-burning velocity of methane/diluent/air mixtures obtained in free-fall experiments

The laminar-burning velocity of methane/air/diluent mixtures has been correlated for variations in unburnt gas temperature (within the range of 293 K to 454 K) and pressures (within the range of 0.5 to 10.4 bar), for as wide a range of mixtures as could he accommodated. The laminar-burning velocity measurements have been deduced from pressure time measurements made in near toro-gravity conditions in a spherical constant volume chamber. The correlations were obtained by a least squares fit of the data to an equation with 12 degrees of freedom. Carbon dioxide, nitrogen, and a 15% carbon dioxide/85% nitrogen mixture were diluents. The mixture of carbon dioxide and nitrogen was used to simulate the products of combustion, thus enabling measurements of the burning velocity to he made that correspond to when exhaust gas residuals (including those arising from exhaust gas recirculation) are present. The data presented here cover higher levels of diluents than previously reported, with up to 60% of either nitrogen or carbon dioxide as part of the fuel. (C) 1998 by The Combustion Institute.