Search

Abstract The development of a new standard for soot emissions proposed by ICAO-CAEP to reduce the environmental impact of civil aviation is moving increasingly research effort on the investigation of sooting flames. Formation and oxidation of the particulate matter are strongly affected by gas temperature, requiring an accurate prediction of the flow field from a numerical point of view. On the other hand, the temperature distribution within the combustor is modified by radiation, which depends on the soot concentration, leading to a very challenging coupled problem. In this work, a series of sensitivity analyses in RANS context are performed on soot, radiation and heat transfer modelling to assess their impact on the prediction of soot emission, gas temperature as well as wall heat fluxes distribution in the context of a high pressure sooting flame which is representative of a RQL combustor. These results are employed to set up a CHT (Conjugate Heat Transfer) simulation, using the multiphysics THERM3D procedure in a loosely-coupled manner where reactive CFD, radiation and heat conduction calculations are computed sequentially with a separate solver in a dedicated framework. These sensitivities can provide useful information for the numerical setup in high-fidelity simulations, as Scale Resolving Simulations. [ABSTRACT FROM AUTHOR]

Incoming standards on NOx emissions are motivating many aero-engines manufacturers to adopt the lean burn combustion concept. However, several technological issues have to be faced in this transition, among which limited availability of air for cooling purpose and thermoacoustics phenomena. In this scenario, standard numerical design tools are not often capable of characterizing such devices. Thus, considering also the difficulties of experimental investigations in a highly pressurized and reactive environment, unsteady scale-resolved CFD methods are required to correctly understand the combustor performances. In this work, a set of scale-resolved simulations have been carried out on the Deutsches Zentrum für Luft- und Raumfahrt (DLR) generic single-sector combustor spray flame for which measurements both in nonreactive and reactive test conditions are available. Exploiting a two-phase Eulerian-Lagrangian approach combined with a flamelet generated manifold (FGM) combustion model, LES simulations have been performed in order to assess the potential improvements with respect to steady-state solutions. Additional comparisons have also been accomplished with scale-adaptive simulation (SAS) calculations based on eddy dissipation combustion model (EDM). The comparison with experimental results shows that the chosen unsteady strategies lead to a more physical description of reactive processes with respect to Reynolds-averaged Navier-Stokes (RANS) simulations. FGM model showed some limitations in reproducing the partially premixed nature of the flame, whereas SAS-EDM proved to be a robust modeling strategy within an industrial perspective. A new set of spray boundary conditions for liquid injection is also proposed whose reliability is proved through a detailed comparison against experimental data. [ABSTRACT FROM AUTHOR]