Sooting and spray characteristics of swirl-stabilized Jet A-1 flames with secondary air injection
Bibliographic record
Abstract
Modern gas turbine engines have been designed to mitigate high NO X emissions through the implementation of Rich-burn, Quick-quench, Lean-burn (RQL) combustion architecture. This staged-combustion approach incorporates secondary air jets, that maintain an overall low temperature within the combustion chamber and have led to a reduction in thermal NO formation. However, its influence on soot formation remains under-reported. To investigate the effects of secondary air injection on soot formation, a model gas-turbine combustor equipped with secondary air jets was employed. The primary air mass flow rate ( m ̇ p ) and secondary air mass flow rate ( m ̇ s ) were systematically varied while maintaining a constant Jet A-1 fuel mass flow rate. Five cases of secondary air substitution, corresponding to 0%, 15%, 30%, 40% and 45% of m ̇ p , were examined. The size and spatial distribution of spray droplets were characterized using digital inline holography (DIH), and soot volume fraction ( f v ) measurements were conducted using simultaneous two-dimensional, two-color auto-compensating planar laser-induced incandescence (AcPLII). Time-averaged soot volume fraction ( f ̄ v ) results revealed an increasing trend in soot formation at the center plane as the substitution percentage was increased from 0% to 40%. However, subsequent decrease in soot formation was observed when substitution was further increased to 45%. The Sauter mean diameter ( D 32 ) of fuel droplets in reacting flow exhibited an increasing trend with increasing secondary air substitution. At substitution levels of 0% and 15%, D 32 decreased with height, characterized by a linear decrease in droplet diameter. In contrast, substitution levels of 30% to 45% showed an increase in D 32 , implying that high temperatures in the primary zone rapidly evaporate smaller droplets, thereby increasing the relative probability of larger droplets. Additionally, secondary air substitution had negligible effect on droplet clustering; rather, inter-droplet spacing appeared to be governed by the strength of the inner re-circulation zone and the temperature in the primary combustion zone. Novelty and significance statement This study examines the effects of secondary air injection jets on soot formation and spray characteristics in a model gas turbine combustor. A key novelty of this work is the measurement of the three-dimensional spray droplet distribution, including droplet diameter and soot volume fraction, within a reacting flow. The results are expected to enhance numerical modeling of polydisperse sprays in such environments. Furthermore, the observed trends in soot volume fraction provide new insights into how the interaction between spray droplets and degree of secondary air substitution influences soot formation.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 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".