Large Eddy Simulation of Lean Blow-Off in a Premixed Swirl Stabilized Flame

Nassini, Pier Carlo; Pampaloni, Daniele; Andreini, Antonio; Meloni, Roberto

doi:10.1115/gt2019-90856

Cited by 10 publications

(6 citation statements)

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“…In any case, this analysis suggests that, despite the flame profile is wrinkled by the identified vortices, there is still a strong anchoring region represented by the high temperature core sustaining the heat release inside the IRZ. As clearly visible from Figure 8 and differently from the operating conditions far from the LBO limits characterized by the presence of hot products also in the ORZ, 3,13,[21][22][23][24][25][26][27][28][29][30] in this case the operability of the flame is ensured exclusively by the IRZ. So, in order to retrieve some clues of the destabilizing mechanism leading to the loss of flame, the discussion will be focused on the analysis of the IRZ and its interaction with the velocity field.…”

Section: Analysis Of the H1 Conditionmentioning

confidence: 77%

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E-POD investigations of turbulent premixed flame dynamics approaching lean blow-out conditions

Meloni¹,

Chiarizia

Nassini

et al. 2023

International Journal of Spray and Combustion Dynamics

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Thanks to the continuous computational power increase, the use of high-fidelity computational fluid dynamics (CFD) simulations is nowadays customary, especially in the gas turbines design process. The extraordinary temporal and spatial detail of such analyses generate large datasets, which must be carefully studied to correlate different quantities and gain information to characterize the behavior of combustor designs. Several advanced post-processing tools have been proposed; however, the Extended-POD (E-POD) holds the greatest potential for turbulent combustion applications when the mutual influence of different quantities is the main goal of the investigation. The present work investigates the application of the E-POD to an LES model of a perfectly-premixed, swirl-stabilized, methane-air flame approaching Lean-Blow-Out. Leveraging the validation against the experimental data at two different operating conditions on a laboratory test case, the numerical model has been used to collect several quantities of interest for shedding light on the flow-flame interaction near the blow-out. The post-processing algorithm has been used to highlight the differences between two conditions approaching the extinction at distinct air-flow velocities. It has been found that, when the burner is operated with a higher velocity, the flame is subjected to a cyclic low-frequency breakdown around the internal recirculation zone, leading to an ingestion of cold products from the external parts of the combustor toward the center. Although other local effects acting on the flame brush have been found in both conditions, they are related mainly to higher order coherent structures with a lower energy content. As a result, their impact onto flame stability is found to be of secondary importance since their limited interaction with flame stabilization. The work shows that E-POD represents a powerful tool for investigating the key features of flame dynamics even at near-blow-out conditions, constituting a valid algorithm for interpreting the results of CFD analyses on gas turbines combustors.

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Section: Analysis Of the H1 Conditionmentioning

confidence: 77%

“…Experimental LBO curve and the results of the numerical model presented in 21,30 (Top). Main test conditions characterizing the H1 and P3 test points used for the numerical investigation (Bottom).…”

Section: Experimental Test Rigmentioning

confidence: 99%

E-POD investigations of turbulent premixed flame dynamics approaching lean blow-out conditions

Meloni¹,

Chiarizia

Nassini

et al. 2023

International Journal of Spray and Combustion Dynamics

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“…Despite the model was originally proposed in RANS framework, the rationale behind it can be extended to LES without particular modifications. However, the two approaches deeply differ in the flame stretch modelling, which was here inspired by previous works focused on the Turbulent Flame Closure [33][34][35]. The present work represents the extension of the Klarmann's model [27] to Large Eddy Simulation, adopting and improving the quenching effects formulation in [33][34][35] thanks to the modelling of the front curvature contribution on the flame stretch.…”

Section: Stretch and Heat Loss Modellingmentioning

confidence: 99%

“…Nevertheless, the flame stretch definition requires the calculation of the front curvature σ c . Despite in previous LES studies it was not modelled [33][34][35]37], in this work this contribution was included by filtering its definition:…”

Section: Stretch and Heat Loss Modellingmentioning

confidence: 99%

Numerical Modeling of Gaseous Partially Premixed Low-Swirl Lifted Flame at Elevated Pressure

Langone

Sedlmaier

Nassini

et al. 2020

Volume 4B: Combustion, Fuels, and Emissions

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Lifted flames have been investigated in the past years for their benefits in terms of NOx emissions reduction for gas turbine applications. In a lifted flame, the flame front stabilized on a position that is significantly detached from the nozzle exit, improving the premixing process before the reaction zone. The distance between the flame front and the nozzle exit is called lift-off height and it represents the main parameter that characterize this type of flame. In the present work, a partially premixed lifted flame employing air-methane mixture is investigated through numerical simulation. Indeed, even if lifted jet flames have been widely studied in the literature, there are only a few examples of lifted partially premixed flames. Nevertheless, this kind of flames assumes an important role considering the current gas turbine applications, since their benefits in terms of stability and low pollutant emissions. This study has been performed with LES calculations using a commercial software suite and the numerical results are compared with experimental data coming from a dedicated campaign held at Karlsruher Institute für Technologie (KIT) on a novel low-swirl injector nozzle. Quenching effects due to strain, curvature and heat loss have been introduced into the combustion model thanks to a correction of the source term in the progress variable equation within the FGM model. The comparison between numerical results and experimental data have been performed in terms of lift-off height and OH* chemiluminescence maps, showing the capability to properly predict the overall flow and to catch flame lift-off even if with an underpredicted height. This points out promising capability of the numerical model in the representation of lifted flames, allowing further investigations of the flame structure otherwise not available from experimental techniques.

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“…In this paper, in order to represent the flame blush, the FGM combustion model with an extended turbulent flame speed closure for the progress variable source term is used. The mathematical implementation of this customized model can be found in Nassini et al [38,39] and Romano et al [40]. The approach implements the heat loss on the flame propagation and the combined effect of the strain rate, resulting in a improvement of the prediction of the flame front position and morphology with benefits in terms of accuracy for both emissions [41,42] and combustion dynamic [43].…”

Section: Numerical Setting Combustion and Turbulence Modelsmentioning

confidence: 99%

Numerical Study of Combustor-Turbine Interaction by Using Hybrid RANS-LES Approach

Tomasello

Andreini

Meloni³

et al. 2022

Volume 6A: Heat Transfer — Combustors; Film Cooling

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The complex flow field of gas turbine lean combustors is meant to reduce NOx emissions and maintain a stable flame by controlling the local temperature and promoting high turbulent mixing. Still, this may produce large flow and temperature unsteady distortions capable of disrupting the aerodynamics and heat transfer of the first high-pressure-turbine cooled nozzle. Therefore, the interaction between the combustion chamber and the turbine nozzle is analyzed first with the help of scale-resolving simulations that notably also include a realistic turbine nozzle cooling system. To determine the nature and severity of the interaction, and the risks associated to performing decoupled simulation, the results of the coupled computer simulation are analyzed and compared with those of decoupled simulations. In this case, the combustor is computed by replacing the turbine nozzle with a discharge convergent with the same throat area, and the conditions at the interface plane are used as inlet boundary conditions for a conventional RANS of the nozzle. The analyses of the coupled and decoupled simulation reveal that the combustion chamber is weakly affected by the presence of the nozzle, whereas the two thermal fields of the nozzle surface differ considerably, as well as the disruption of the film cooling by the incoming flow distortions.

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Large Eddy Simulation of Lean Blow-Off in a Premixed Swirl Stabilized Flame

Cited by 10 publications

References 0 publications

E-POD investigations of turbulent premixed flame dynamics approaching lean blow-out conditions

E-POD investigations of turbulent premixed flame dynamics approaching lean blow-out conditions

Numerical Modeling of Gaseous Partially Premixed Low-Swirl Lifted Flame at Elevated Pressure

Numerical Study of Combustor-Turbine Interaction by Using Hybrid RANS-LES Approach

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