Vortex Breakdown in a Swirl-Stabilized Combustor

Umeh, Chukwueloka O. U.; Rusak, Zvi; Gutmark, Ephraim

doi:10.2514/1.59756

Cited by 1 publication

(5 citation statements)

References 27 publications

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“…In all cases computed, the reaction zone is upstream of the leading stagnation point and wraps around the vortex breakdown separation zone. This is similar to flow and reaction zone patterns observed in the experimental study in figures 4 and 5 in Umeh et al (2012). We note that, in realistic situations, the velocity inside the breakdown zone is slightly negative due to viscous diffusion of momentum from the rotating bulk into the breakdown zone.…”

Section: Solid-body Rotationsupporting

confidence: 87%

“…The computed results from the present approach capture the major trends of the nonlinear behaviour predicted in the numerical simulations of Choi et al (2007). The results are also supported by the detailed discussions in Rusak et al (2002) and Umeh et al (2012). These discussions emphasize the interactions between flow dynamics and reaction as manifested by the interaction between flow convection, vorticity stretching and baroclinic effects.…”

supporting

confidence: 68%

“…The case with u x (0, y) = 0 was studied in Rusak (1998) and describes how general azimuthal vorticity profiles at the inlet can be included. The inlet conditions may represent the flow behind a vane guide vortex generator in a fuel injector as found in the experiments of Gupta et al (1984Gupta et al ( , 1998, Paschereit et al (1998) and Umeh et al (2012). They are also common in numerical simulations of reacting flows with swirl (Grinstein & Fureby 2005;Grinstein et al 2006;Choi et al 2007).…”

Section: Mathematical Modelmentioning

confidence: 98%

“…These outlet conditions are appropriate for a sufficiently long open pipe, where the flow downstream of the reaction zone settles naturally on a parallel (columnar) state ahead of the outlet, see experiments of Umeh et al (2012) and numerical simulations of Choi et al (2007). Along the pipe centreline at y = 0, the axisymmetry assumption requires Ψ (x, 0) = 0 for 0 x x 0 .…”

Section: Mathematical Modelmentioning

confidence: 98%

“…Combustion assisted by swirl is a fundamental scientific problem where the interaction of fluid dynamics and reaction heat release forms complicated flow states, see, for example, Gupta, Lilley & Syred (1984), Sivasegaram & Whitelaw (1991), Gutmark et al (1992), Gupta, Lewis & Qi (1998), Paschereit, Gutmark & Weisenstein (1998, 2000, Lieuwen & Yang (2005), Syred (2006), Umeh, Rusak & Gutmark (2012), Durox et al (2013) and Candel et al (2014). These states include a reaction zone and a central recirculation (breakdown) zone (CRZ) around the domain centreline, at high flow swirl levels above a certain critical value, that serves as a non-invasive flame stabilizer.…”

Section: Introductionmentioning

confidence: 99%

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Vortex breakdown in premixed reacting flows with swirl in a finite-length circular open pipe

et al. 2016

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A global analysis of steady states of low Mach number inviscid premixed reacting swirling flows in a straight circular finite-length open pipe is developed. We focus on modelling the basic interaction between the swirl and heat release of the reaction. For analytic simplicity, a one-step first-order Arrhenious reaction kinetics is considered in the limit of high activation energy and infinite Peclet number. Assuming a complete reaction with chemical equilibrium upstream and downstream of the reaction zone, a nonlinear partial differential equation is derived for the solution of the flow stream function downstream of the reaction zone in terms of the specific total enthalpy, specific entropy and circulation functions prescribed at the inlet. Several types of solutions of the nonlinear ordinary differential equation for the columnar flow case describe the outlet states of the flow in a long pipe. These solutions are used to form the bifurcation diagram of steady reacting flows with swirl as the inlet swirl level is increased at a fixed heat release from the reaction. The approach is applied to two profiles of inlet flows, the solid-body rotation and the Lamb-Oseen vortex, both with constant profiles of the axial velocity, temperature and mixture reactant mass fraction. The computed results provide theoretical predictions of the critical inlet swirl levels for the appearance of vortex breakdown states and for the size of the breakdown zone as a function of the inlet flow swirl level, Mach number and heat release of the reaction. For the inlet solid-body rotation, flow is decelerated to breakdown as the inlet swirl is increased above the critical swirl level, and there is a delay in the appearance of breakdown with the increase of the heat release of the reaction. For the inlet Lamb-Oseen vortex at low values of heat release, the critical swirl for breakdown is decreased with the increase of heat release while, at high values of heat release, the appearance of breakdown is delayed to higher incoming flow swirl levels with the increase of heat release. The analysis sheds light on the global dynamics of low Mach number reacting flows with swirl and vortex breakdown and on the interaction between vortex breakdown and heat release that affects the shape of the reaction zone in the domain.

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Section: Solid-body Rotationsupporting

confidence: 87%

supporting

confidence: 68%