Numerical study of non-reacting flowfields of a swirling trapped vortex ramjet combustor

In this work, 3D numerical investigations of a trapped vortex combustor operated in different swirling flow conditions are performed by solving Reynolds-averaged Navier-Stokes equations with Reynolds-stress model. Emphasis is placed on the non-reacting flowfield characteristics and the stability of the locked vortex. Validation is performed first by comparing the present results with experimental data available. It shows that the Reynolds-stress model can provide good predictions for flows with a swirl number up to 0.98. It is also found that the cavity vortex can be trapped well in flows with different swirl numbers. To further study the "locked" vortices, flow disturbances are introduced to the trapped vortex combustor via suddenly increasing swirl number from 0.6 to 0.98. The transient simulation results reveal that the cavity vortex is highly resistant to the flow disturbances and is still well trapped in the cavity, while vortex shedding of the conventional breakdown vortex is observed in the presence of the flow disturbances. Turbulence intensity and kinetic energy are found to be significantly increased by approximately 300%, which indicates that the fuel-air mixing can be dramatically improved. This study shows that the swirling trapped vortex combustor is an alternative promising robust and efficient combustor concept. (C) 2018 Elsevier Masson SAS. All rights reserved.