Stabilisation of Turbulent Concentric and Swirling Flames Based on Flow and Mixing Pattern Investigations

Schmittel, Peter; Prade, Bernd; Hoffmann, Stefan; Lenze, B.

doi:10.1002/3527601996.ch6

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“…Merkle et al [8] and Schmittel et al [9]. They measured concentration, velocity and temperature fields and determined an intersection of favorable conditions as possible areas for flame stabilization.…”

Section: Introductionmentioning

confidence: 99%

Similarity Issues of Kerosene and Methane Confined Flames Stabilized by Swirl in Regard to the Weak Extinction Limit

Marinov

Kern

Zarzalis

et al. 2012

Flow Turbulence Combust

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One of the most promising methods for reducing NO x emissions of jet engines is the lean combustion process. For realization of this concept the percentage of air flowing through the combustor dome has to be drastically increased, which implies high volume fluxes in the primary zone of the combustion chamber and represents a substantial challenge in regard to the flame stabilization. Swirl motion is thus applied to the air flux by the swirl generator and decisively contributes to the flame stabilization. The current paper reviews an atmospheric investigation of a burner configuration in regard to the weak extinction limit, comprising a confined nonpremixed swirl-stabilized flame. The burner can be supplied with either kerosene or after a small adaption with natural gas (methane). Therefore, a comparison of a kerosene-fuelled flame (spray flame) to a natural gas fuelled one (methane flame) can be performed. Both are realized by almost identical burner configuration and at identical conditions. The main idea of this work is to align the stability characteristics of both flames by means of similarity. However, fundamental differences regarding the flame structures of the flames are detected through in-flame measurements. This determines the limits of the current approach and motivates an appropriate choice of flame modeling. Flow Turbulence Combust (2012) 89:73-95 A Area [m 2 ] AFR Air-Fuel Ratio [-] α Thermal diffusivity C Reaction progress [-] Da Damköhler-number [-] Da t turbulent Damköhler-number [-] D Diameter of comb. chamber [m] D/d Flow expansion ratio [-] d Nozzle throat diameter [m] D Angular momentum [kg·m 2 /s] IRZ Inner Recirculation Zonė I Axial momentum [kg·m/s] k turbulent kinetic energy, mass specific Ka Karlowitz-number [-] L t integral length scale [m] L length of contact zone [m] LBO Lean blowout LDA Laser Doppler Anemometrẏ M Mass flow rate [kg/s] ORZ Outer Recirculation Zone PDA Particle Dynamics Analysis PERM Partially Evaporated, Rapidly Mixed Pe Peclet-number [-] p Pressure in the chamber [bar] r radial position [m] R 0 Nozzle exit radius [m] Re t turbulent Reynolds-number S Swirl Number [-] S t turbulent flame velocity [m/s] S lam laminar flame velocity [m/s] SMD Sauter Mean Diameter [m] T Temperature [K] U 0 Nozzle exit volumetric velocity at referenced condition [m/s] U lim Nozzle exit volumetric velocity at LBO [m/s] UHC Unburned hydrocarbons [-] u mean axial velocity [m/s] u', v', w' velocity fluctuations [m/s] u 2 , v 2 , w 2 normal Reynolds stresses [m 2 /s 2 ] x Axial position [m] p/p normalized pressure loss [%] 3D Three dimensional Flow Turbulence Combust (2012) 89:73-95 75 2D Two dimensional χ, Mass flow rate split [-] φ Equivalence ratio [-] ν kinematic viscosity [m 2 /s] λ 1/φ τ time scale [s]

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Section: Introductionmentioning

confidence: 99%