Mathematical Modeling of Swirling Flames of Pulverized Coal: What Can Combustion Engineers Expect From Modeling?

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Abstract
The present study is concerned with mathematical modeling of swirling pulverized coal flames. The attention is focused on the near burner zone properties of high-and low-NOx flames issued from an Aerodynamically Air Staged Burner of 3.4 MW thermal input. The swirling combusting flows are calculated using the k–ε model and second-order models of turbulence. The Eulerian balance equations for enthalpy and mass fractions of oxygen, volatiles, carbon monoxide and final combustion products (CO2 + H2O) are solved. The Lagrangian particle tracking is accompanied by appropriate models of coal devolatilization and char combustion. Nitric oxide emissions are calculated using a NOx post-processor for thermal-, prompt- and fuel-NO. The objective of this paper is to examine whether the engineering information required for designing industrial burners is obtainable through the mathematical modeling. To this end, the flame computations, including NO emissions, are compared with the measured in-flame data. The guidelines as to the combination of physical submodels and model parameters needed for quality predictions of different flame types are given. The paper is a shorter version of our recent ASME publication (Weber et al., 1993).