Conditional moment closure in a bagasse-fired boiler

First order conditional moment closure (CMC) is applied in a two-phase, three-dimensional model of a bagasse-fired boiler to obtain predictions of CO and NO in the flue gas which are compared to experiment. The system being solved is essentially gas phase and sources from solid particles are included in the governing instantaneous equations, which yields a new form of the CMC equation differing from previous applications of CMC to the analogous problem of turbulent sprays. The sources of fuel and moisture have magnitudes specified by CFD submodels for evaporation, devolatilization and char burnout, and are given presumed forms in mixture fraction space. A combination of CMC with the steady laminar flamelet model (SLFM) is explored to reduce the computational expense of the model. Flexible handling of arrays of conditional quantities based on efficiency criteria is also proposed in the regions of the spatial grid solved by CMC.