Large eddy simulation of fuel sensitivity in a realistic spray combustor I. Near blowout analysis

Understanding combustion and flame stabilization of alternate fuels is necessary to establish their use in mainstream aviation. An Eulerian-Lagrangian (EL) large eddy simulation (LES) study is conducted using a fully compressible solver for a Referee Rig combustor, developed within the National Jet Fuel Combustion Program, (NJFCP). The Referee Rig contains multiple swirlers, dilution jets, and effusion holes, mimicking the complex flow-field in a real gas turbine combustor. Conditions as in the experiments for near blowout (NBO) operation are simulated for two fuels identified by NJFCP: a baseline fuel (A2) and an alternate fuel (C1). Time-averaged LES results are shown to provide a reasonable match against the experimental droplet statistics and OH * chemiluminescence data for both the fuels. Several post-processing tools, such as, conditional averaging, flame index, chemically explosive mode analysis (CEMA) are used to understand flame stabilization mechanism and burning behavior under NBO condition. Flame anchor point is shown to be premixed, but most heat release results from fuel pockets burning in the shear layer in a nonpremixed manner. Pressure signatures at various locations and other time-varying properties show fuelsensitive effects, even though the time-averaged behavior is similar between A2 and C1. When compared to A2, C1 shows a higher premixed burning and it is shown to be dependent on the slower burning behavior of C1 at NBO.

Automated summary

Understanding combustion and flame stabilization of alternate fuels is crucial for their use in aviation. This study uses large eddy simulation to simulate a real gas turbine combustor and investigate the burning behavior and flame stabilization mechanism of two fuels. The results show that the flame anchor point is premixed, but most heat release comes from fuel pockets burning in a nonpremixed manner.