Experimental assessment of the lean blow-off in a fully premixed annular combustor

Ciardiello, Roberto; Skiba, A.; Gordon, Robert L.; Mastorakos, Epaminondas

doi:10.1016/j.expthermflusci.2019.109994

Cited by 18 publications

(8 citation statements)

References 26 publications

(44 reference statements)

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“…Figure 1 shows a picture of the premixed annular combustor (d) , along with a schematic of the top view (a), the side view (b), and of an individual burner (c). The apparatus was adapted and developed from the one from Worth and Dawson [21,22] and Allison et al [23] and it was previously employed for an investigation of the LBO behaviour of a multi-burner configuration [24]. All details of the setup can be found in these references, thus a shorter description is provided in this paper.…”

Section: Premixed Annular Combustormentioning

confidence: 99%

“…A detailed description of the flame shape and characteristics at stable conditions can be found in Ref. [24]. The stable flame appeared attached to the bluff bodies and the individual flames seemed to merge in the inter-burner region, suggesting high level of interaction, especially for the 18-burner case.…”

Section: Lean Ignition Limitsmentioning

confidence: 99%

“…Figures 3a and 3b report the graphs with the lean ignition limits for the 12-and 18-burner configurations, compared to the LBO stability limits (retrieved from Ref. [24]). The stability curves are presented in terms of equivalence ratio vs mixture velocity, as commonly reported for flames stabilised in the presence of a flameholder [1].…”

Section: Lean Ignition Limitsmentioning

confidence: 99%

“…Thus, there is lack of information on the lean ignition transient and ignition probability when the fourth phase of flame propagation (light-round) is involved. The aim of this work is to fill this gap by carrying out an experimental investigation in a premixed annular combustor, previously employed in study on thermoacoustic instabilities [21][22][23], stable ignition [7] and, recently, lean blow-off [24]. Two configurations were employed, composed of 12 and 18 burners respectively, to assess the effect of inter-burner distance on the ignition transient.…”

Section: Introductionmentioning

confidence: 99%

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Ignition Probability and Lean Ignition Behavior of a Swirled Premixed Bluff Body Stabilized Annular Combustor

Ciardiello

Pathania

Allison

et al. 2021

Journal of Engineering for Gas Turbines and Power

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An experimental investigation was performed in a premixed annular combustor equipped with multiple swirl, bluff body burners to assess ignition probability and provide insights into the mechanisms of failure and of successful flame propagation. Two configurations were employed, with 12 and 18 burners, mixture velocity was varied between 10 and 30 m/s, and equivalence ratio between 0.58 and 0.68. Ignition was initiated by a sequence of sparks and "ignition" is defined as successful ignition of the whole annular combustor. Mechanism of success and failure of the ignition process was investigated via high-speed imaging of OH*chemiluminescence. Lean ignition limits were evaluated and compared to the lean blow-off limits. It was found that failure is linked to the trapping of the flame kernel inside the inner recirculation zone (IRZ) of a single burner, followed by localised quenching on the bluff body due to heat losses. In contrast, for a successful ignition, it was necessary for the flame kernel to propagate to the adjacent burner. Finally, the ignition probability(Pign) was obtained for different spark locations. It was found that sparking inside the recirculation zone resulted in Pign~0 for most conditions, while Pign increased moving the spark away from the bluff body or placing it between two burners and peaked to Pign~1 when the spark was located downstream in the combustion chamber. The results provide information on the most favorable conditions for achieving ignition and could help design and optimization of realistic gas turbine combustors.

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Section: Premixed Annular Combustormentioning

confidence: 99%

Section: Lean Ignition Limitsmentioning

confidence: 99%

Section: Lean Ignition Limitsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Ignition Probability and Lean Ignition Behavior of a Swirled Premixed Bluff Body Stabilized Annular Combustor

Ciardiello

Pathania

Allison

et al. 2021

Journal of Engineering for Gas Turbines and Power

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show abstract

“…Thus, there is lack of information on the lean ignition transient and ignition probability when the fourth phase of flame propagation (light-round) is involved. The aim of this work is to fill this gap by carrying out an experimental investigation in a premixed annular combustor, previously employed in studies on thermoacoustic instabilities [21][22][23], stable ignition [7] and, recently, lean blow-off [24]. Two configurations were employed, composed of 12 and 18 burners respectively, to assess the effect of inter-burner distance on the ignition transient.…”

Section: Introductionmentioning

confidence: 99%

Ignition Probability and Lean Ignition Behaviour of a Swirled Premixed Bluff Body Stabilised Annular Combustor

Ciardiello¹,

Pathania²,

Allison³

et al. 2021

Preprint

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An experimental investigation was performed in a premixed annular combustor equipped with multiple swirl, bluff body burners to assess the ignition probability and to provide insights into the mechanisms of failure and of successful flame propagation. The experiments are done at conditions that are close to the lean blow-off limit (LBO) and hence the ignition is difficult and close to the limiting condition when ignition is not possible. Two configurations were employed, with 12 and 18 burners, the mixture velocity was varied between 10 and 30 m/s, and the equivalence ratio (φ) between 0.58 and 0.68. Ignition was initiated by a sequence of sparks (2 mm gap, 10 sparks of 10 ms each) and "ignition" is defined as successful ignition of the whole annular combustor. The mechanism of success and failure of the ignition process and the flame propagation patterns were investigated via high-speed imaging (10 kHz) of OH * chemiluminescence. The lean ignition limits were evaluated and compared to the lean blow-off limits, finding the 12-burner configuration is more stable than the 18-burner. It was found that failure is linked to the trapping of the initial flame kernel inside the inner recirculation zone (IRZ) of a single burner adjacent to the spark, followed * Address all correspondence to this author.by localised quenching on the bluff body probably due to heat losses. In contrast, for a successful ignition, it was necessary for the flame kernel to propagate to the adjacent burner or for a flame pocket to be convected downstream in the chamber to grow and start propagating upwards. Finally, the ignition probability (P ign ) was obtained for different spark locations. It was found that sparking inside the recirculation zone resulted in P ign ∼ 0 for most conditions, while P ign increased moving the spark away from the bluff body or placing it between two burners and peaked to P ign ∼ 1 when the spark was located downstream in the combustion chamber, where the velocities are lower and the turbulence less intense. The results provide information on the most favourable conditions for achieving ignition in a complex multi-burner geometry and could help the design and optimisation of realistic gas turbine combustors.

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Impact of Flame-Generated Turbulent Intensity and Flame Speed on the Low-Order Modelling of Light-Round

Mesquita

Ciardiello

Mastorakos

2022

Flow Turbulence Combust

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A previously-developed low-order Lagrangian stochastic model for ignition of premixed and non-premixed flames is modified in this paper to improve the numerical prediction of the light-round process in premixed annular combustors. The model refinements take into account Flame-Generated Turbulent Intensity (FGTI) and impose a turbulent flame speed correlation to the flame particles using expressions from the literature. For this, using RANS CFD results as an input, the model was applied to simulate the ignition transient in a premixed, swirled bluff body stabilised annular combustor to characterise the light-round time, both in stable conditions and close to the stability limits. Several cases were analysed, where flame speed and fuel were varied and light-round times were compared to experimental results. The proposed modifications improved the accuracy of the light-round time predictions, suggesting that FGTI may be an important phenomenon to be modelled. This modified model coupled with dilatation and the Peter’s assumption for the turbulent flame speed resulted in considerable improvement for the light-round time calculation for the explored range of parameters. This is an attractive feature considering the low computational cost of these simulations, which can be run in a single core of a local workstation. The improved model can help gas turbine engineers assess the ignition behaviour of annular combustors early in the design process.

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Experimental assessment of the lean blow-off in a fully premixed annular combustor

Cited by 18 publications

References 26 publications

Ignition Probability and Lean Ignition Behavior of a Swirled Premixed Bluff Body Stabilized Annular Combustor

Ignition Probability and Lean Ignition Behavior of a Swirled Premixed Bluff Body Stabilized Annular Combustor

Ignition Probability and Lean Ignition Behaviour of a Swirled Premixed Bluff Body Stabilised Annular Combustor

Impact of Flame-Generated Turbulent Intensity and Flame Speed on the Low-Order Modelling of Light-Round

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