Large-Eddy Simulation of Light-Round in an Annular Combustor With Liquid Spray Injection and Comparison With Experiments

Abstract

The light-round is defined as the process by which the flame initiated by an ignition spark propagates from burner to burner in an annular combustor, eventually leading to a stable combustion. Combining experiments and numerical simulation, it was recently demonstrated that under perfectly premixed conditions this process could be suitably described by large eddy simulation (LES) using massively parallel computations. The present investigation aims at developing light-round simulations in a configuration that is closer to that found in aero-engines by considering liquid nheptane injection. The large-eddy simulation of the ignition sequence of a laboratory scale annular combustion chamber comprising sixteen swirled spray injectors is carried out with a mono-disperse Eulerian approach for the description of the liquid phase. The objective is to assess this modeling approach of the two-phase reactive flow during the ignition process. The simulation results are compared in terms of flame structure and light-round duration to the corresponding experimental images of the flame front recorded by a high-speed intensified CCD camera and to the corresponding experimental delays. The dynamics of the flow is also analyzed to identify and characterize mechanisms controlling flame propagation during the light-round process.

Impact of dynamic modelling of the flame subgrid scale wrinkling in large-Eddy simulation of light-round in an annular combustor

“…The main characteristics of the numerical setup are given in this section. Several numerical details were already discussed in [18,19]. Hence, the relevant aspects are summarized in what follows, and then the attention is mainly focused on the dynamic approach for subgridscale wrinkling, which is the objective of the present study.…”

“…The liquid phase is modeled through a mono-disperse Eulerian-Eulerian approach. This simplified methodol- ogy has been shown to provide a good compromise between accuracy and CPU cost [18,19], and the same numerical setup is retained in the present calculations.…”

“…Boileau et al [15] were the first able to investigate the full ignition of a helicopter engine through LES. More recently, massively parallel LES were employed in the premixed gaseous injection case [16,17] and with liquid fuel [18,19] to analyze the MICCA-Spray chamber. Similarly, Xia et al [20] carried out LES on the annular chamber studied in [14] employing Automatic Mesh Refinement (AMR) and a Perfectly Stirred Reactor (PSR) approach for chemistry description.…”

“…However, several modelling hypotheses were included in the various numerical setups that deserve further investigations. Among them, most numerical simulations [15][16][17][18][19] relied on an algebraic model formulation for the flame subgrid-scale wrinkling factor. This assumption may, however, not be adapted for transient and timedependent phenomena such as ignition and flame propagation [21].…”

Simulations of flame propagation during the ignition process in an annular multiple-injector combustor

“…This investigation confirmed that LES is a promising method in studying ignition process in the annular combustor. Lancien et al (2017) studied flame propagation initialized by an ignition spark from burner to burner. In this investigation, the light-round simulation was developed in a configuration that was closer to aero engines with the liquid fuel of n -heptane.…”