Cinema particle imaging velocimetry time history of the propagation velocity of the base of a lifted turbulent jet flame

Upatnieks, Ansis; Driscoll, James F.; Ceccio, Steven L.

doi:10.1016/s1540-7489(02)80230-9

Cited by 42 publications

(21 citation statements)

References 20 publications

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“…The coupling of the bulging turbulent eddy and the entraining flow causes an anticlockwise rotation of the flame and distorts it into a 'hook' structure. Such hook structures have been observed frequently in experimental measurements of lifted flames (for instance figure 7 in Kelman et al Kelman et al (1998), and is consistent with experimental measurements by Upatnieks et al (2002Upatnieks et al ( , 2004 and Boxx et al (2009a,b). In the example shown here, the large eddy is even strong enough to cause an extinction hole above the leading edge location.…”

Section: Time Evolution Of the Flame Basesupporting

confidence: 87%

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Mechanisms of flame stabilisation at low lifted height in a turbulent lifted slot-jet flame

et al. 2015

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A turbulent lifted slot-jet flame is studied using direct numerical simulation (DNS). A one-step chemistry model is employed with a mixture-fraction-dependent activation energy which can reproduce qualitatively the dependence of the laminar burning rate on the equivalence ratio that is typical of hydrocarbon fuels. The basic structure of the flame base is first examined and discussed in the context of earlier experimental studies of lifted flames. Several features previously observed in experiments are noted and clarified. Some other unobserved features are also noted. Comparison with previous DNS modelling of hydrogen flames reveals significant structural differences. The statistics of flow and relative edge-flame propagation velocity components conditioned on the leading edge locations are then examined. The results show that, on average, the streamwise flame propagation and streamwise flow balance, thus demonstrating that edge-flame propagation is the basic stabilisation mechanism. Fluctuations of the edge locations and net edge velocities are, however, significant. It is demonstrated that the edges tend to move in an essentially two-dimensional (2D) elliptical pattern (laterally outwards towards the oxidiser, then upstream, then inwards towards the fuel, then downstream again). It is proposed that this is due to the passage of large eddies, as outlined in Su et al. (Combust. Flame, vol. 144 (3), 2006, pp. 494-512). However, the mechanism is not entirely 2D, and out-of-plane motion is needed to explain how flames escape the high-velocity inner region of the jet. Finally, the time-averaged structure is examined. A budget of terms in the transport equation for the product mass fraction is used to understand the stabilisation from a time-averaged perspective. The result of this analysis is found to be consistent with the instantaneous perspective. The budget reveals a fundamentally 2D structure, involving transport in both the streamwise and transverse directions, as opposed to possible mechanisms involving a dominance of either one direction of transport. It features upstream transport balanced by entrainment into richer conditions, while on the rich side, upstream turbulent transport and entrainment from leaner conditions balance the streamwise convection.

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Section: Time Evolution Of the Flame Basesupporting

confidence: 87%

“…The appearance of flame islands upstream of the main flame has been observed in many experimental studies of lifted flames (Upatnieks et al 2002;Lyons et al 2007;Boxx et al 2009aBoxx et al ,b, 2014Gordon et al 2012). The laser-based diagnostic techniques used in these studies rely on measurements in 2D sheets.…”

Section: Time Evolution Of the Flame Basementioning

confidence: 96%

Mechanisms of flame stabilisation at low lifted height in a turbulent lifted slot-jet flame

et al. 2015

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“…5. Approximately 4,000 point measurements from different radial positions were grouped together to form a probability density map for three axial positions (z/d=8, 11,14). There is a clear progression from a predominantly mixing condition (z/d=8) to vigorous flame burning (z/d=14) that corresponds to the transition from mixing only to mixing combined with ignition and flame stabilization.…”

Section: Combustion Statistics At Flame Stabilizationmentioning

confidence: 99%

“…It hasalso been proposed [8,9] that hot,product containing eddies rotate upstream, entrain preheated reactants, and facilitate reaction. Recent studies using scalar fieldimaging [10]and PIV [11]showed evidence oftheimportance ofsuch recirculation atthestabilization region.…”

mentioning

confidence: 99%

Simultaneous laser raman-rayleigh-lif measurements and numerical modeling results of a lifted turbulent H2/N2 jet flame in a vitiated coflow

Cabra

Myhrvold

Chen

et al. 2002

Proceedings of the Combustion Institute

318

293

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“…Chen and Bilger [6] have investigated the stabilization mechanisms of lifted laminar flames based on the triple flame concept. Experimental measurements on lifted jet flames has been extensively made by advanced laser-based diagnostics techniques, such as particle image velocimetry (PIV), laser doppler velocimetry (LDV), laser-induced fluorescence (LIF) and Raman-Rayleigh scattering [9,14,[20][21][22]24], and the detailed structure included with velocity profiles, temperature and species mass fraction profiles, and images of instantaneous flame cross-sections, were obtained to explore the stabilization mechanisms of lifted jet flames. However, velocity data are limited at the base of the lifted jet flame, especially for the cases with high Reynolds numbers and low Damköhler numbers, which are exemplary of practical burners.…”

Section: Introductionmentioning

confidence: 99%

An Experimental Investigation of the Turbulence Structure of a Lifted H2/N2 Jet Flame in a Vitiated Co-Flow

Masri

Bilger

2006

Flow Turbulence Combust

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Measurements of mean velocity components, turbulent intensity, and Reynolds shear stress are presented in a turbulent lifted H 2 /N 2 jet flame as well as non-reacting air jet issuing into a vitiated co-flow by laser doppler velocimetry (LDV) technique. The objectives of this paper are to obtain a velocity data base missing in the previous experiment data of the Dibble burner and so provide initial and flow field data for evaluating the validity of various numerical codes describing the turbulent partially premixed flames on this burner. It is found that the potential core is shortened due to the high ratio of jet density to co-flow density in the non-reacting cases. However, the existence of flame suppressed turbulence in the upstream region of the jet dominates the length of potential core in the reacting cases. At the centreline, the normalized axial velocities in the reacting cases are higher than the non-reacting cases, and the relative turbulent intensities of the reacting flow are smaller than in the non-reacting flow, where a self-preserving behaviour for the relative turbulent intensities exists at the downstream region. The profiles of mean axial velocity in the lifted flame distribute between the non-reacting jet and non-premixed flame both in the axial and radial distributions. The radial distributions of turbulent kinetic energy in the lifted flames exhibit a change in distributions indicating the difference of stabilisation mechanisms of the two lifted flame. The experimental results presented will guide the development of an improved modelling for such flames. Nomenclature r radial distance (mm) x axial distance from the burner exit (mm) d nozzle exit diameter (mm) u mean local fluid axial velocity (m/s) v mean local fluid radial velocity (m/s) U 1 co-flow velocity (m/s) U 0 jet velocity at nozzle exit (m/s) U excess fluid velocity (U = u − U 1 ) (m/s) U m the maximum value of U (m/s) u axial velocity fluctuation (m/s) 62 Z. WU ET AL. v radial velocity fluctuation (m/s) u vReynolds shear stress (m 2 /s 2 ) k turbulence kinetic energy, k = (u 2 + 2v 2 )/3 T mean local temperature (K) Q fluid flow rate (slm) b radial distance at which excess velocity is half value of U m (mm) s offset distance of U m from the real centre (mm) H liftoff height (mm) Y mole fraction TP thermal power (kJ/s) ρ density (kg/m 3 ) ReReynolds number equivalence ratio

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Cinema particle imaging velocimetry time history of the propagation velocity of the base of a lifted turbulent jet flame

Cited by 42 publications

References 20 publications

Mechanisms of flame stabilisation at low lifted height in a turbulent lifted slot-jet flame

Mechanisms of flame stabilisation at low lifted height in a turbulent lifted slot-jet flame

Simultaneous laser raman-rayleigh-lif measurements and numerical modeling results of a lifted turbulent H2/N2 jet flame in a vitiated coflow

An Experimental Investigation of the Turbulence Structure of a Lifted H2/N2 Jet Flame in a Vitiated Co-Flow

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