Visualization of soot inception in turbulent pressurized flames by simultaneous measurement of laser-induced fluorescence of polycyclic aromatic hydrocarbons and laser-induced incandescence, and correlation to OH distributions

Geigle, Klaus Peter; O'Loughlin, William; Hadef, Redjem; Meier, Wolfgang

doi:10.1007/s00340-015-6075-3

Cited by 44 publications

(32 citation statements)

References 56 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For the same flame, various laser-based measurements with low repetition rates are presented in Refs. [3,5,6].…”

Section: Combustor and Operating Conditionmentioning

confidence: 99%

“…Measurements at other operating conditions indicate that the structure of flow field is representative also of flames with other values of pressure, P and φ, whereas the location and rates of soot formation then change significantly [3,5,6]. The study of transient dynamics of soot in the remainder of this work, however, is limited to the single operating condition specified above.…”

Section: Numerical Simulationmentioning

confidence: 99%

“…The availability of accurate experimental data for technically relevant combustors under well-defined conditions yet still remains limited. Recently our group has reported measurements of velocity field, temperature and soot concentration as well as visualization of OH and PAH for an aero-engine model combustor at elevated presssure [3,5,6]. The data is available on request and has since been used for improvement and validation of large eddy simulation (LES) calculations [7][8][9].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Time-resolved study of transient soot formation in an aero-engine model combustor at elevated pressure

Stöhr

Geigle

Hadef

et al. 2019

Proceedings of the Combustion Institute

View full text Add to dashboard Cite

The mechanisms of transient formation and oxidation of soot in an aero-engine model combustor at elevated pressure are studied for the first time using a combination of high-speed simultaneous stereo-PIV and OH-PLIF and results from a recent detailed LES. A combined analysis of experiment and LES shows that the highly transient and intermittent evolution of soot in this combustor is governed by an unsteady interplay of distinct pockets of burned gas in the inner recirculation zone (IRZ) with either relatively rich or relatively lean composition. The former originate from reaction of fuel-rich unburned gas, whereas the latter result from additional admixture of secondary air further downstream. The analysis further enables distinction and localization of premixed and diffusion-type flame fronts within the flame zone. The time-resolved complementary measurements of velocity field and flame structure allow accurate tracking of both the burned gas pockets and soot filaments. It is seen that soot generally forms in the rich pockets if their residence time in the IRZ is sufficient, whereas oxidation occurs in the lean zones carrying OH. Correlating the dynamics of flow field and soot indicates that the intermittency of soot is driven by an intermittent flow of lean burned gas into the IRZ that affects the residence time of rich pockets. The results suggest that the formation of soot might be further reduced by a proper adjustment of secondary air injection aiming at a sufficient and more constant recirculation of lean burned gas. A remarkably good agreement of measured and simulated instantaneous flame structures is observed, indicating that flow field and gas-phase reactions are well predicted by the LES. The experimental insights into the transient mechanisms of soot formation and oxidation, on the other hand, may provide useful input for LES soot models where deviations from measurements are generally larger.

show abstract

“…For the same flame, various laser-based measurements with low repetition rates are presented in Refs. [3,5,6].…”

Section: Combustor and Operating Conditionmentioning

confidence: 99%

Section: Numerical Simulationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Time-resolved study of transient soot formation in an aero-engine model combustor at elevated pressure

Stöhr

Geigle

Hadef

et al. 2019

Proceedings of the Combustion Institute

View full text Add to dashboard Cite

show abstract

“…Simultaneous measurements revealed that the distribution of soot and OH changes with the addition of dilution air. Soot no longer propagates downstream in the central recirculation zone (CRZ) where the OH is dispersed due to the dilution air (Geigle et al 2015b). Recently, their work has focused on soot-turbulence interactions, revealing that soot forms in rich pockets when residence times are favorable, while soot is oxidized by the OH present in the lean zones (Stöhr et al 2019).…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation of Soot Production and Oxidation in a Lab-Scale Rich–Quench–Lean (RQL) Burner

Helou

Skiba

Mastorakos

2020

Flow Turbulence Combust

View full text Add to dashboard Cite

Swirl-stabilized, turbulent, non-premixed ethylene-air flames at atmospheric pressure with downstream radially-injected dilution air were investigated from the perspective of soot emissions. The velocity and location of the dilution air jets were systematically varied while the global equivalence ratio was kept constant at 0.3. The employed laser diagnostics included 5 kHz planar laser-induced fluorescence (PLIF) of OH, 10 Hz PAH-PLIF, and 10 Hz laser-induced incandescence (LII) imaging of soot particles. OH-PLIF images showed that the reaction zone widens with dilution, and that regions with high OH-LIF signal shift from the shear layer to the axis of the burner as dilution increases. Dilution is effective at mitigating soot formation within the central recirculation zone (CRZ), as evident by the smaller PAH-containing regions and the much weaker LII signal. Dilution is also effective at halting PAH and soot propagation downstream of the dilution air injection point. The high momentum dilution air circulates upstream to the root of the flame and reduces fuel penetration lengths, induces fast mixing, and increases velocities within the CRZ. Soot intermittency increased with high dilution velocities and dilution jet distances up to two bluff body diameters from the burner inlet, with detection probabilities of < 5% compared to 50% without dilution. These results reveal that soot formation and oxidation within the RQL are dependant on the amount and location of dilution air injected. This data can be used to validate turbulent combustion models for soot.

show abstract

“…The example of flame extinction will be discussed in greater detail later when we compare Large-Eddy Simulations used for finite-rate kinetic effects against local flame extinction inferred from fast OH-PLIF, which has allowed very thorough validation of the sub-grid turbulent combustion model. Recent developments in PLIF include the imaging of NO [61], soot precursors like Poly-cyclic Aromatic Hydrocarbons (PAH) [62], H atom [63] and HCO [64]. The technical difficulties, resolution issues, lasers and cameras needed are discussed in the original papers.…”

Section: Experimental Diagnosticsmentioning

confidence: 99%

Turbulent Combustion Modelling and Experiments: Recent Trends and Developments

Giusti

Mastorakos

2019

Flow Turbulence Combust

View full text Add to dashboard Cite

The development of better laser-based experimental methods and the fast rise in computer power has created an unprecedented shift in turbulent combustion research. The range of species and quantities measured and the advent of kHz-level planar diagnostics are now providing great insights in important phenomena and applications such as local and global extinction, pollutants, and spray combustion that were hitherto unavailable. In simulations, the shift to LES allows better representation of the turbulent flow in complex geometries, but despite the fact that the grid size is smaller than in RANS, the push towards realistic conditions and the need to include more detailed chemistry that includes very fast species and thin reaction zones emphasize the necessity of a sub-grid turbulent combustion model. The paper discusses examples from current research with experiments and modelling that focus on flame transients (self-excited oscillations, local extinction), sprays, soot emissions, and on practical applications. These demonstrate how current models are being validated by experimental data and the concerted efforts the community is taking to promote the modelling tools to industry. In addition, the various coordinated International Workshops on non-premixed, premixed, and spray flames, and on soot are discussed and some of their target flames are explored. These comprise flames that are relatively simple to describe from a fluid mechanics perspective but contain difficult-to-model combustion problems such as extinction, pollutants and multi-mode reaction zones. Recently, swirl spray flames, which are more representative of industrial devices, have been added to the target flames. Typically, good agreement is found with LES and some combustion models such as the progress variable-mixture fraction flamelet model, the Conditional Moment Closure, and the Transported PDF method, but predicting soot emissions and the condition of complete extinction in complex geometries is still elusive.

show abstract

Visualization of soot inception in turbulent pressurized flames by simultaneous measurement of laser-induced fluorescence of polycyclic aromatic hydrocarbons and laser-induced incandescence, and correlation to OH distributions

Abstract: Visualization of soot inception in turbulent pressurized flames by simultaneous measurement of laserinduced fluorescence of polycyclic aromatic hydrocarbons and laser-induced incandescence, and correlation to OH distributions, Appl. Phys. B 119 (2015) 717-730.

Cited by 44 publications

References 56 publications

Time-resolved study of transient soot formation in an aero-engine model combustor at elevated pressure

Time-resolved study of transient soot formation in an aero-engine model combustor at elevated pressure

Experimental Investigation of Soot Production and Oxidation in a Lab-Scale Rich–Quench–Lean (RQL) Burner

Turbulent Combustion Modelling and Experiments: Recent Trends and Developments

Contact Info

Product

Resources

About