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Modeling coal particles in turbulent coal flames is a challenging but nonetheless critical step for predicting flame characteristics. Traditional approaches such as Reynolds-Averaged Navier-Stokes (RANS) coupled with Lagrangian solvers are unable to correctly predict particle concentrations and velocities in complex systems. This study shows how Large Eddy Simulations (LES) coupled with an Eulerian solver can address those issues. Previous Direct Numerical Simulations and Stokes number analysis suggest that LES has the capabilities to resolve all the turbulent length scales affecting coal particles in a coal flame and could therefore lead to more accurate simulation. The effects of fluid aerodynamics on the particle motion in the near field region of non-reacting coaxial particle-laden jets were simulated using LES. The Direct Quadrature Method of Moments (DQMOM) was used to track the particle phase in an Eulerian framework. Simulation results were compared to experimental data and accurately modeled a wide range of particle behaviors, such as particle jet waviness, spreading, break up, particle clustering and segregation, in different conditions. Simulations also predicted the mean axial velocity along the centerline for both the gas phase and the solid phase with a maximum error of 12% relative to experimental data. This study therefore provides a solid validation of the LES with DQMOM approach to model particles in turbulent flows and justifies its use for coal flame simulations.

The primary purpose of the study is to obtain physical insight into the stability of an oxy-coal flame as a function of changing primary gas composition ( CO 2 and O 2 ). Flame stability was measured by Zhang et al. using optical measurements of the flame stand-off distance in a 40 kW pilot facility. Large Eddy Simulations (LESs) of the facility were performed using a multi-scale simulation tool and provide additional insight into the experimentally observed data. The importance of factors such as heterogeneous reactions, radiation or wall temperature can be better understood thanks to simulations. The effects of three parameters on the flame stand-off distance were studied. Simulation predictions were compared to experimental data using the data collaboration method. Overall, this study shows that high-fidelity LES simulations combined with experimental data can yield a deeper understanding of very complex coal flames, indicate where experimental uncertainties lie and be a valuable tool for design, retrofit and scale-up of oxy-coal burners.

The goal of this study is to show that large eddy simulation (LES) combined with the direct quadrature method of moments (DQMOM) can accurately predict coal flame ignition mechanisms and more generally be a valuable tool for predicting and understanding coal flame characteristics. A validation study of the ARCHES LES tool is performed. LES is applied to a pulverized coal jet flame ignited by a preheated gas flow. A DQMOM has been developed to track the particle phase in an Eulerian framework. The simulation results are compared qualitatively and quantitatively to experimental observations for different inlet stoichiometric ratios. LESs are able to capture the various combustion regimes observed during flame ignition and to accurately model the flame stand-off distance sensitivity to the stoichiometric ratio. The gas temperature and coal burnout predictions are also examined and show good agreement with experimental data. Overall, this study shows that high-fidelity LESs combined with DQMOM can yield a dee...

A "hemispheres-in-cell" geometry is provided for prediction of colloid retention during transport in porous media. This new geometry preserves the utilities provided in the Happel sphere-in-cell geometry; namely, the ability to predict deposition for a range of porosities, and representation of the influence of neighboring collectors on the fluid flow field. The new geometry, which includes grain to grain contact, is justified by the eventual goal of predicting colloid deposition in the presence of energy barriers, which has been shown in previous literature to involve deposition within grain to grain contacts for colloid:collector ratios greater than approximately 0.005. In order to serve as a platform for predicting deposition in the presence of energy barriers, the model must be shown capable of quantitatively predicting deposition in the absence of energy barriers, which is a requirement that was not met by previous grain to grain contact geometries. This paper describes development of the fluid flow field and particle trajectory simulations for the hemispheres-in-cell geometry in the absence of energy barriers, and demonstrates that the resulting simulations compare favorably to existing models and experiments. A correlation equation for predicting collector efficiencies in the hemispheres-in-cell model in the absence of energy barriers was developed via regression of numerical results to dimensionless parameters.