Abstract
This chapter discusses the role of swirling jet systems in combustion control. An axisymmetric swirl combustor configuration is described in the chapter. It involves a primary fuel nozzle, within which air is passed through a swirler arrangement to mix and atomize the fuel. Coupling swirling flow motion with sudden expansion to the full combustor diameter provides an effective way of enhancing the fuel-air mixing and stabilizing combustion. A hybrid simulation approach is used in the chapter to investigate the flow patterns in an axisymmetric swirl combustor configuration. Effective inlet boundary conditions are based on the velocity data obtained from solving Reynolds-averaged Navier–Stokes (RANS) equations or actual laboratory measurements at the outlet of a fuel-injector nozzle. Large-eddy simulation (LES) is used to study the unsteady nonreactive swirl flow dynamics downstream. The initial inlet conditions are important in regulating the behavior of the swirling flow entering a sudden expansion area, including swirl and radial numbers, inlet length, and characteristic velocity profiles. The swirl of sufficient strength produces an adverse pressure gradient that can promote flow reversal or vortex breakdown and the coupling between swirl and sudden expansion instabilities depends on the relative length of the inlet. The flow is found to be very sensitive to the detailed nature of the radial velocity profiles.
Published Version
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