Experimental and Computational Study of Non-Reacting Vortex Breakdown in a Swirl-Stabilized Combustor

Umeh, Chukwueloka O. U.; Rusak, Zvi; Gutmark, Ephraim; Villalva, Rodrigo; Cha, Dong

doi:10.2514/6.2009-643

Cited by 2 publications

(1 citation statement)

References 17 publications

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“…RANS/URANS methods are very effective but require higher spatial discretizations than LES methods [Taglia et al, 2004;Bonaldo, 2007;Umeh et al, 2009]. They have also been proposed by INL for modeling the VHTR LP [Johnson, 2007].…”

Section: Six-equation Rsm Modelsmentioning

confidence: 99%

Swirling jets for the mitigation of hot spots and thermal stratification in the VHTR lower plenum.

Rodríguez¹

2011

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The literature indicates that a prismatic-core very high temperature reactor can experience thermal stratification and hot spot issues in the lower plenum (LP). This research hypothesizes that the complex thermalhydraulic phenomena in the LP requires a sophisticated computational fluid dynamics (CFD) code with state-of-the-art turbulence models and advanced swirling jet technology to mitigate the two issues. The primary research goals were to increase the heat transfer and mixing capacity of swirling jets, extend swirling jet theory, and to apply those advancements for the mitigation of the thermalhydraulic issues. First, it was demonstrated that the Fuego CFD code successfully modeled a set of key LP thermalhydraulic phenomena. Thereafter, a helicoid vortex swirl model was developed to investigate the impact of the swirl number (S) on mixing and heat transfer. The development of azimuthal and axial velocities that are solely functions of S permitted the analysis of the central recirculation zone's (CRZ) impact on the LP flow field. At this point, several characteristics were found in common between the helicoid vortex and other axisymmetric, Newtonian, incompressible vortices found in the literature. This observation resulted in a more fundamental understanding of how vortices behave, and which traits can be exploited for the purpose of maximizing heat transfer and mixing. Because the CRZ is a strong function of the azimuthal and axial velocities, shaping those velocity profiles had a substantial impact. Eventually, this led to the discovery that vortices may be expressed as alternating series that expand geometrically with odd exponents. This helped corroborate that the 15 axisymmetric vortices discussed in this research are part of a vortex family with seven common traits. This also led to the development of new vortices that are based on one or two series terms that satisfy the Navier-Stokes equations and conservation of mass. In addition, the impact of Reynolds number and swirl decay were explored in order to further quantify their impact. Finally, the above theories and modeling insights were applied towards a comprehensive set of LP calculations that showed that the swirling jets mitigated the entrainment and hot spot issues, while resulting in a reasonable pressure drop. Contents

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Section: Six-equation Rsm Modelsmentioning

confidence: 99%

Swirling jets for the mitigation of hot spots and thermal stratification in the VHTR lower plenum.

Rodríguez¹

2011

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Unsteady RANS for Simulation of High Swirling Non-Premixed Methane-Air Flame

Solmaz¹,

Uslu²,

Uzol³

2014

50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference

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Highly swirled non-premixed methane-air combustion is studied using Unsteady RANS. The increased CPU power at present times makes RANS solutions a viable design methodology for industrial applications. LES, Large Eddy Simulation, is still a bit far away from being the routine approach as a design tool in industry. The confined non-premixed TECFLAM S09C flame is investigated because of its similarity with gas turbine engine combustors. A block structured hexahedral computational mesh is used for the whole domain for higher numerical accuracy. A first-order accurate Euler Implicit technique is used for the temporal discretization of the transient terms. Realizable k-ε turbulence model is employed in order to account for the turbulent flow effects on the flow field and chemical reactions. Results of fast and two step reactions are compared with finite rate chemistry. Results show that, the best solution is obtained by using Finite Rate Eddy Dissipation Model.The infinitely fast chemistry approach is not capable of predicting the reaction delay that is clearly observed in the experiments. Instead, the fast chemistry approach show reaction zones in the close vicinity of the swirler where the fuel-air mixing is not well achieved for the reactions to take place in such a short distance. The flow field is directly affected by the heat release rate that is determined by the fuel air mixing and combustion model. Nomenclature S= swirl number ρ = density U = velocity U θ ,W = circumference velocity U r ,u = axial velocity A = area k = kinetic energy ε = eddy dissipation rate R = swirler radius D = swirler diameter r = radial location CRZ = central recirculation zone EDM = eddy dissipation model

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Experimental and Computational Study of Non-Reacting Vortex Breakdown in a Swirl-Stabilized Combustor

Cited by 2 publications

References 17 publications

Swirling jets for the mitigation of hot spots and thermal stratification in the VHTR lower plenum.

Swirling jets for the mitigation of hot spots and thermal stratification in the VHTR lower plenum.

Unsteady RANS for Simulation of High Swirling Non-Premixed Methane-Air Flame

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