Investigation of the effect of dilution air on soot production and oxidation in a lab scale Rich-Quench-Lean (RQL) burner

Helou, Ingrid El; Skiba, A.; Mastorakos, Epaminondas; Sidey, Jennifer A.

doi:10.2514/6.2019-1436

Cited by 5 publications

(9 citation statements)

References 12 publications

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“…In both cases, the secondary air stream is deactivated, and the height of the dilution jets is h = 47 mm. Previous experimental studies in this burner have shown that these conditions drastically affect soot emission [25,26,27,28]. Similar trends have been observed via numerical investigations in similar conditions with a slightly leaner global equivalence ratio [48].…”

Section: Investigated Burnersupporting

confidence: 85%

“…The investigated burner, developed at the University of Cambridge, is based on a bluff-body swirl-stabilised ethylene/air burner operating at atmospheric pressure [25,26,27]. A picture and a schematic of the rig are given in Ref.…”

Section: Investigated Burnermentioning

confidence: 99%

“…Herein, Large Eddy Simulation (LES) with the Conditional Moment Closure (CMC) combustion model is used to simulate an ethylene lab-scale burner that has been developed at the University of Cambridge and replicates the major features of the RQL concept [25,26,27], similar to the DLR burner [12,13], but with different air-fuel injection systems (axial vs angled annular) and extra degrees of freedom (variable dilution jet location, range of dilution ratios, spray capability). In particular, this work evaluates the reasons why dilution air drastically reduces the overall soot emission in the Cambridge RQL burner, as shown by measurements of soot volume fraction [26,27,28] and PSDs inflame [28] and at the exhaust [25,28]. The experiments reveal that this device is characterised by high soot production in the primary zone and strong oxidation due to dilution.…”

Section: Introductionmentioning

confidence: 99%

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Comprehensive soot particle size distribution modelling of a model Rich-Quench-Lean burner

Gkantonas

Sirignano

Giusti

et al. 2020

Fuel

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Soot particle size distribution (PSD) evolution in an ethylene lab-scale swirl Rich-Quench-Lean (RQL) combustor is investigated using a detailed physicochemical sectional soot model coupled with the Conditional Moment Closure turbulent combustion model and Large Eddy Simulation. The aim is to develop predictive capability for the local soot PSD and to explore differences in soot PSDs with different conditions of a burner configuration widely used in practice for emissions control. Two such conditions are studied by varying the airflow provided in the burner primary and dilution regions, which has a drastic effect on soot emission as shown by previous experiments. The results show a reasonably good agreement with experiments for the mean reaction zone and soot locations and their variations with dilution. The predicted PSDs at the burner exit are fairly well captured for the high-dilution condition but show too few and too small particles for the dilution-free condition, which may be due to an overprediction of the oxidation rates or the unity Lewis number assumption used here that enhances penetration of soot towards the oxidiser stream. The results are analysed to reveal the hierarchy of reaction pathways during soot evolution and indicate how dilution air modifies the soot PSD within the primary zone. In particular, the presence of dilution leads to a broadly sustained uni-modal soot

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Section: Investigated Burnersupporting

confidence: 85%

Section: Investigated Burnermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Comprehensive soot particle size distribution modelling of a model Rich-Quench-Lean burner

Gkantonas

Sirignano

Giusti

et al. 2020

Fuel

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“…A schematic of the burner can be found in Fig. 1, and is identical to the one used in Tracy et al (2018), Giusti et al (2018), El Helou (2019. Gaseous fuel is injected along the axis of the burner through a straight circular channel 4 mm in diameter that passes through the centre of the bluff body.…”

Section: Burner Setupmentioning

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

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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.

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“…However, a low number of ISRs with arbitrary spacing can still be useful as a rough estimate of soot emissions and inexpensive parametric analysis. Preliminary investigations in the ethylene Cambridge Rich-Quench-Lean (RQL) combustor [10,11,21,[45][46][47] [49], which is also a target flame of the International Sooting Flame workshop.…”

Section: Resultsmentioning

confidence: 99%

Soot Emission Simulations of a Single Sector Model Combustor Using Incompletely Stirred Reactor Network Modeling

Gkantonas

Foale

Giusti

et al. 2020

Journal of Engineering for Gas Turbines and Power

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The simulation of soot evolution is a problem of relevance for the development of low-emission aero-engine combustors. Apart from detailed CFD approaches, it is important to also develop models with modest computational cost so a large number of geometries can be explored, especially in view of the need to predict engine-out soot particle size distributions (PSDs) to meet future regulations. This paper presents an approach based on Incompletely Stirred Reactor Network (ISRN) modeling that simplifies calculations, allowing for the use of very complex chemistry and soot models. The method relies on a network of Incompletely Stirred Reactors (ISRs), which are inhomogeneous in terms of mixture fraction but characterized by homogeneous conditional averages, with the conditioning performed on the mixture fraction. The ISRN approach is demonstrated here for a single sector lean-burn model combustor operating on Jet-A1 fuel in pilot-only mode, for which detailed CFD and experimental data are available. Results show that reasonable accuracy is obtained at a significantly reduced computational cost. Real fuel chemistry and a detailed physicochemical sectional soot model are consequently employed to investigate the sensitivity of ISRN predictions to the chemical mechanism chosen and to provide an estimate of the soot particle size distribution at the combustor exit.

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Investigation of the effect of dilution air on soot production and oxidation in a lab scale Rich-Quench-Lean (RQL) burner

Cited by 5 publications

References 12 publications

Comprehensive soot particle size distribution modelling of a model Rich-Quench-Lean burner

Comprehensive soot particle size distribution modelling of a model Rich-Quench-Lean burner

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

Soot Emission Simulations of a Single Sector Model Combustor Using Incompletely Stirred Reactor Network Modeling

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