Large-eddy simulations (LES) is a powerful approach that can correctly address the unsteady nature of flows in gas turbine combustion chambers.  While LES becomes affordable for industrial applications, it still requires grid sizes that are larger than the flame thickness. Moreover, the interactions between the flame and small turbulent scales, unresolved in LES,  have to be modeled. The Thickened Flame Model (TFM), initially designed for premixed flames \[1,2\], is an attractive methodology which ensures that the flame front is properly resolved on the LES mesh, and will be considered in the present study. The chemistry in this approach is integrated directly and thus additional assumptions about the flame structure are not required.

It has been shown recently that by coupling TFM with an Adaptive Mesh Refinement (AMR) strategy, high accuracy can be achieved without prohibitive computational costs. The TFM-AMR model has demonstrated a good agreement with experimental data of a gaseous stratified burner \[3\].

In this work, the objective is to extend the TFM-AMR approach to flame simulations involving two-phase flows.  An Eulerian-Lagrangian formalism is here considered for the simulations. A simplified injection model is selected \[4\], where spray parcels are injected in spherical form following a prescribed diameter distribution, thus bypassing the spray atomization stage.

 The CORIA Rouen Spray Burner (CRSB) set-up \[5\] is selected as a validation burner for the present study because of its complete and accurate database which includes droplet’s diameter, velocity, and temperature measurements. This canonical unconfined spray burner has well-defined boundary conditions and consists of a hollow-cone spray injector which is surrounded by an annular non-swirled air co-flow. N-heptane is considered as a liquid fuel. The resulting jet flame is lifted and has a complex structure that includes an inner lean partially premixed wrinkled flame, an outer principally laminar diffusion flame front, and an enclosed in-between region of hot gases, where droplet’s evaporation rates are enhanced and fuel pyrolysis reactions are taking place.

 A reduced 36 species n-heptane mechanism is used for an accurate chemistry description. In the beginning, the TFM-AMR modeling approach is validated for spray conditions on a laminar one-dimensional configuration. Then the performance of the model is assessed on the CRSB burner set-up. In order to validate the numerical set-up as well as the fuel injection strategy, results are first obtained for the non-reacting conditions and compared to the experimental ones. Finally, the results of the reacting configuration are analyzed and discussed. The focus is made on the flame shape and its structure.

Bibliography :

\[1\] T. D. Butler and P. J. O’Rourke. A numerical method for two-dimensional unsteady reacting flows. Symposium (International) on Combustion.

\[2\] O. Colin, F. Ducros, D. Veynante, and T. Poinsot. A thickened flame model for large-eddy simulations of turbulent premixed combustion. Physics of Fluids, 12(7):1843–1863, 2000.

\[3\] C. Mehl, S. Liu, Y.C. See, and O. Colin. Les of a stratified turbulent burner with a thickened flame model coupled to adaptive mesh refinement and detailed chemistry. Joint Propulsion Conference, AIAA Propulsion and Energy Forum, 2018.

\[4\] L. Guedot. Development of numerical methods for the characterization of large scale structures in aeronautical swirl burners. Application to multi-points injectors. Ph.D. thesis, INSA Rouen Normandie, 2015.

\[5\] A. Verdier. Experimental study of dilute spray combustion. Ph.D. thesis, INSA Rouen Normandie, 2017.


Large Eddy Simulation of a Turbulent Spray Burner Using Thickened Flame Model and Adaptive Mesh Refinement

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

Turbo Expo - Virtual Conference

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.