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This paper provides a preliminary study of two different methods to handle the limitations of the Lagrangian point-force approach in the context of unstructured LES solvers. Large deviations in mass, momentum, and energy exchanges between the gas and liquid phases may occur if the assumptions of the point-force approach are not verified. In particular, the point-force approach considers the particles to be subgrid-scale phenomena but the use of more and more refined grids for the carrier flow allowed by today's computer power leads to cell sizes of the order or smaller than the particle diameters. Several methods are found in the literature to tackle this problem. However, they are usually suited for structured solvers. In the case of unstructured solvers handling several hundred thousand particles in unsteady flows, such methods are far too expensive. In this work, two original methods adapted for spray calculation in unstructured solvers are implemented and compared: the particle-bursting method, and the multigrid method. In this preliminary study, only the correction on the evaporation model is studied, with drag being neglected. Both methods greatly improve the accuracy of the evaporation model but only the multigrid method is independent of the Eulerian mesh refinement. The results presented show that the two methods are relevant to correct the evaporation source terms when the limits of the point-force model are reached. However, the study should be extended to consider the impact of the methods on the drag model calculation and the effects on the interaction with a reactive gaseous phase. [ABSTRACT FROM AUTHOR]

This paper proposes a method for modeling soot when performing Large Eddy Simulation of complex geometries. To obtain a good trade-off between CPU cost and accuracy, soot chemistry is included via a tabulated flamelet approach, combined to a turbulent combustion model for Large Eddy Simulation based on a simplified description of chemistry. A semi-empirical soot model is chosen and validated on laminar premixed and counterflow diffusion flames. A proposed procedure enables to calculate radiation with a Discrete Ordinates Method approach and optimized spectral models. The developed soot model is applied to a real configuration, being the combustion chamber of a helicopter engine. To evaluate the importance of radiative heat losses, two cases are studied, using either adiabatic conditions or accounting for radiative heat gains/loss. [ABSTRACT FROM AUTHOR]

Because of compressibility criteria, fuel used in aeronautical combustors is liquid. Their numerical simulation therefore requires the modeling of two-phase flames, involving key phenomena such as injection, atomization, polydispersion, drag, evaporation and turbulent combustion. In the present work, particular modeling efforts have been made on spray injection and evaporation, and their coupling to turbulent combustion models in the Large Eddy Simulation (LES) approach. The model developed for fuel injection is validated against measurements in a non-evaporating spray in a quiescent atmosphere, while the evaporation model accuracy is discussed from results obtained in the case of evaporating isolated droplets. These models are finally used in reacting LES of a multipoint burner in take-off conditions, showing the complex two-phase flame structure. [ABSTRACT FROM AUTHOR]