MODEL COMPARISONS WITH DROP TUBE COMBUSTION DATA FOR VARIOUS DEVOLATILIZATION SUBMODELS

Predictions of a two-dimensional, axisymmetric combustion model, using various devolatilization submodel options, are compared with new expe rimental data from a near-laminar, drop-tube furnace. Included in the devolatilization submodels that were tested are the commonly used empi rical one- and two-step models and a chemical, coal network model with parameters based on coal structure. The goals of this work were to ev aluate the latter approach as compared with the simple, empirical appr oach usually used-in such calculations and to assess the role of turbu lence in a near-laminar reacting flow. Comparisons were made for carbo n conversion, radially averaged oxygen and near-effluent NOx concentra tions, for a range of coal types and equivalence ratios. The predictio ns quantify an ignition delay which is consistent with the measurement s. Computations with the fundamental, chemical devolatilization submod el gave superior predictions of mass loss when the coal type was withi n the interpolation range of the submodel parameter database. Accuracy declined significantly when the coal type was outside the interpolati on range. Inclusion of the effects of turbulence was required to accou nt for the observations. Near-effluent NO predictions with the chemica l submodel agreed with measured NOx values to within an average of abo ut 20 percent.