This paper describes a new, efficient technique for computing first-order spatial dependence of a furnace flame. The technique, called the moving boundary flame model, creates dynamic state variables that track the size of the flame within the furnace. The approximation is appropriate for full plant training simulators, control system analysis, and engineering analyses in which a higher fidelity model than a point reactor model is needed. In comparison to the point reactor models, the one dimensional spatial dependence should improve the accuracy of distributed quantities such as heat transfer and reaction rates over the range fuel and air flow conditions that exist in normal and abnormal operation. The model is not intended to replace detailed multi-dimension flow models of the furnace. Although the flame model is a first principles model, the accuracy depends on data from a more detailed combustion simulation or experimental data for volume-averaged parameters such as the turbulent mixing coefficient for fuel and air, radiative and conductive heat transfer coefficients, and ignition and extinction conditions. These inputs can be viewed as tuning parameters used normalize the moving boundary model to a more accurate model at a particular operating point. The expected application for the model is dynamic system analysis for burner diagnostics and controls. Burner diagnostics and controls are expected to be areas for major development to reduce emissions and improve efficiency of commercial fossil fuel power plants
