Large eddy simulation of a semi-industrial scale coal furnace using non-adiabatic three-stream flamelet/progress variable model

Abstract

To describe the combustion process in the burners with complicated configuration used in the industrial applications, a non-adiabatic three-stream flamelet/progress variable (FPV) model for simulating pulverized coal combustion (PCC) is proposed in the context of large eddy simulation (LES). A conserved scalar associated with oxidizer split is introduced to characterize mixing of different oxidizer streams while the manifold of enthalpy defect is incorporated to account for heat losses. As a first step towards real industrial applications, the present model is evaluated by simulating a semi-industrial swirl-stabilized pulverized coal flame. Qualitative analyses are first carried out to explore the details of the coal combustion behaviors in this complicated configuration burner. We find that the coal particle reaction is closely related to the distribution of the oxidizer split. In addition, the results show that the reaction in the swirl induced internal recirculation zone is mainly generated by homogeneous combustion while the heterogeneous reaction dominates in the downstream region. Quantitative comparisons among the present model, the eddy break up model and the experiments are also conducted. The results from the flamelet model agree well with the experimental data and outperform those from the eddy break up model. However, discrepancies still exist in species concentrations at certain area, which may be further improved by high-fidelity devolatilization model in the future study.