Nonpremixed Flamelet Statistics at Flame Base of Lifted Turbulent Jet Nonpremixed Flames

Noda, Susumu; Mori, Hisaya; Hongo, Yusuke; Nishioka, Makihito

doi:10.1299/jsmeb.48.75

Cited by 6 publications

(6 citation statements)

References 28 publications

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“…This data supports the idea that the premixed propagation is what dictates flame stabilization rather than the extinction of the diffusion flame [1], and since some recent experiments are still investigating scalar dissipation as the controlling parameter [20], hybrid approaches may still be viable [10]. A related study by Ahmed and Mastorakos [22] also focuses on ignition and subsequent upstream propagation of lifted flames.…”

Section: Discussionsupporting

confidence: 73%

Observations on Upstream Flame Propagation in the Ignition of Hydrocarbon Jets

McCraw

Moore

Lyons

2007

Flow Turbulence Combust

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A variety of investigators have attempted to characterize the mechanisms of how reaction zones stabilize, or propagate, against incoming reactants, particularly in stable lifted jet flames both laminar and turbulent. In this paper, experiments are described that investigate the characteristics of upstream flame propagation in turbulent hydrocarbon jet flames. An axisymmetric, gaseous turbulent jet mixing in air has been selectively ignited at downstream positions to assess the upstream propagation of the bulk reaction zone. The farthest axial position that permitted the reaction zone to propagate upstream after application of the ignition source, referred to as the "upper propagation limit", or UPL, is determined for a variety of jet and air co-flow parameters. There is an inverse relationship between the upper propagation limit position and the jet Reynolds number. Conversely, there is a direct relationship between the upper propagation limit and the co-flow velocity. Interpretation of the results is related to the velocity at the stoichiometric surface. Global discussion is made as to what these results imply about the stabilization and propagation of turbulent lifted jet flames.

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Section: Discussionsupporting

confidence: 73%

Observations on Upstream Flame Propagation in the Ignition of Hydrocarbon Jets

McCraw

Moore

Lyons

2007

Flow Turbulence Combust

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“…In reacting flows D can vary substantially in different regions of the flow owing to its dependence on temperature. Experimental investigations of the behaviour of the statistics of χ include, for example, Namazian, Schefer & Kelly (1988); Gladnick, LaRue & Samuelsen (1990); Boyer & Queiroz (1991) ;Nandula, Brown & Pitz (1994); Everest et al (1995); Chen & Mansour (1996); Buch & Dahm (1998) ;Fielding, Schaffer & Long (1998); Karpetis & Barlow (2002); Tsurikov & Clemens (2002) ;Su & Clemens (2003); Barlow & Karpetis (2004); Noda et al (2005); Wang, Clemens & Varghese (2005); and Markides & Mastorakos (2006). Complementary numerical studies, primarily using direct numerical simulations (DNS), have also verified some of the experimental findings, e.g.…”

Section: Introductionmentioning

confidence: 80%

On the effect of heat release in turbulence spectra of non-premixed reacting shear layers

Knaus

Pantano

2009

J. Fluid Mech.

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Velocity, mixture fraction and temperature spectra obtained from five direct numerical simulations of non-reacting and reacting shear layers, using the infinitely fast chemistry approximation, are analysed. Two different global chemical reactions corresponding to methane and hydrogen combustion with air, respectively, are considered. The effect of heat release, i.e. density variation, on the inertial and dissipation turbulence subrange of the spectra is investigated. Analysis of the database supports the experimentally available measurements of spectra in turbulent reacting flows showing that heat release effects can be scaled out by utilizing Favre-averaged (density-weighted) largescale turbulence quantities. This is supported by the simulation results for velocity and mixture fraction in our moderate-Reynolds-number flows but it appears to be less supported in the dissipation subrange of the temperature spectra. The departure from universal scaling using Favre-averaged quantities in the temperature spectrum, which is evident in the dissipation subrange, appears to be caused by the strong nonlinearity of the state relationship relating the mixture fraction to the temperature, as has been suggested previously. These effects are less pronounced at intermediate wavenumbers.Analysis suggests that the nonlinear state relationship and the spectra of mixture fraction moments can be used to reconstruct the temperature spectrum across the flow. Moreover, the governing equation for the temperature variance is analysed to identify a possible surrogate for the overall rate of dissipation of temperature fluctuations and their corresponding dissipation length scale. This scaling analysis is then used to separate planes across the shear layer where the temperature dissipation length scale is alike that of the mixture fraction from regions where smaller length scales are present, and are evidenced in the dissipation subrange using Kolmogorov scaling. In our simulations, these regions correspond to the centre of the shear layer and the mean flame location. The new estimate for the temperature dissipation length scale is able to collapse the compensated spectra profiles at all planes across the shear layer for all simulations.

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“…Different approaches have been used for this purpose. In experimental studies of hydrocarbon flames, commencement of chemiluminescence of CH * (Su et al 2006), CH PLIF (Watson et al 2000;Hult et al 2005;Noda et al 2005;Lyons et al 2007) or OH PLIF (Boxx et al 2009a,b;Gordon et al 2012) has frequently been used as the flame-base marker. The excited CH * radical is short-lived and thought to mark the instantaneous reaction zone (Su et al 2006).…”

Section: Normalised Flame Indexmentioning

confidence: 99%

“…Although the presentation here is slightly different, we have verified that the final result is the same edge speed as used first by Pantano (2004) to study extinction holes and later by Hawkes et al (2007a,b) to study extinction and reignition, and also by Chakraborty & Mastorakos (2008) to study ignitions. Tiggelen 1966; Kalghatgi 1984;Namazian et al 1988;Miake-Lye & Hammer 1989;Pitts 1989;Takahashi & Schmoll 1991;Schefer et al 1994a,b;Muniz & Mungal 1997;Schefer 1997a,b;Hasselbrink & Mungal 1998;Kelman, Eltobaji & Masri 1998;Schefer & Goix 1998;Tacke et al 1998;Takahashi, John Schmoll & Katta 1998;Brown, Watson & Lyons 1999;Watson et al 1999Watson et al , 2000Watson et al , 2002Watson et al , 2003Han & Mungal 2000;Maurey et al 2000;Baillot & Demare 2002;Mansour 2003Mansour , 2004Noda et al 2005), and therefore there have been numerous questions raised about out-of-plane motion and its potential role in flame stabilisation. Out-of-plane motion of the flame is the consequence of two effects: flow motion and flame propagation.…”

Section: Normalised Flame Indexmentioning

confidence: 99%

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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Nonpremixed Flamelet Statistics at Flame Base of Lifted Turbulent Jet Nonpremixed Flames

Cited by 6 publications

References 28 publications

Observations on Upstream Flame Propagation in the Ignition of Hydrocarbon Jets

Observations on Upstream Flame Propagation in the Ignition of Hydrocarbon Jets

On the effect of heat release in turbulence spectra of non-premixed reacting shear layers

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

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