Experimental and Numerical Investigations of Structure and Stability of Premixed Swirl-Stabilized CH<sub>4</sub>/O<sub>2</sub>/CO<sub>2</sub> Flames in a Model Gas Turbine Combustor
Bibliographic record
Abstract
Premixed CH 4 /O 2 /CO 2 flames were studied experimentally and numerically in a swirl-stabilized combustor. The bulk throat velocity of the incoming combustible mixture was maintained constant at 5.2 m/s. The oxygen fraction of the O 2 /CO 2 oxidizer was kept constant at 60 vol %, while the effect of the equivalence ratio was examined from the blowout limit to the flashback one. The LES computational model was successfully validated through comparisons with experimental data in terms of axial and radial temperature profiles, as well as predicted OH* concentration maps versus visual flame appearance. Three different flame structures were observed while varying the equivalence ratio, namely, (I) double conical flame, (II) corner-stabilized flame, and (III) swirl-stabilized (V-shaped) flame. The double conical flame is observed at low equivalence ratios near the blowout limit. This flame stabilizes within both the inner and outer shear layers and has two distinct reaction zones with two inner recirculation zones (IRZs) separated by a colder, reaction-free corner recirculation zone (CRZ). The corner-stabilized flame is observed at higher equivalence ratios. The downstream reaction zone diminishes and merges with the upstream one to form a flame that stabilizes within a reacting CRZ. Increasing the equivalence ratio further induces a transition to the typical V-shape of swirl-stabilized flames with significantly stronger IRZ and weaker CRZ. This flame is thus stabilized by its IRZ. The V-shape prevails until flashback occurs when the hot reaction zone moves closest to the burner throat.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".