Pressure dependence of synergistic soot formation in ethylene/propane co-flow diffusion flames
Bibliographic record
Abstract
This study investigates the influence of pressure on synergistic soot formation in co-flow laminar diffusion flames of ethylene/propane mixtures (1–6 atm). Radially resolved fields of soot volume fraction, temperature, and the soot absorption function, E ( m ) , were obtained using three-color line-of-sight attenuation and spectral soot emission techniques. Synergistic promotion of soot formation was observed at all pressures, but its strength varied with pressure: at 1 atm, the peak soot volume fraction increased from 1.24 ppm in neat ethylene to 1.52 ppm with 5% carbon from propane, whereas at 6 atm it increased only marginally from 86.4 ppm to 90.3 ppm. Normalized soot yield revealed the strongest nonlinearity at 2 atm, followed by 3 atm, then 1 atm, 4 atm, 5 atm, and 6 atm. Temperatures for different mixtures at a given pressure were similar and primarily controlled by soot loading and associated radiative losses. The measurements show that E ( m ) varies both spectrally and spatially; values are notably lower than the commonly assumed 0.26 in nascent soot regions near the flame base and higher elsewhere. This variation demonstrates that a constant E ( m ) can misestimate soot volume fraction depending on location and wavelength. Despite substantial differences in soot concentration among mixtures, soot maturity distributions were broadly similar. These results provide high-fidelity data for model validation and emphasize the need to account for wavelength-dependent optical properties when quantifying soot at elevated pressures. Novelty and significance statement This study provides the first multi-parameter characterization of synergistic soot formation in ethylene/propane diffusion flames at elevated pressures. By introducing a wavelength-dependent absorption function, E ( m ) , it captures spatial variation in soot maturity and improves quantification. The results demonstrate persistent synergistic effects across pressures and yield novel mechanistic insights, including rate-limiting steps, with direct relevance to predictive soot models for high-pressure combustion systems using blended fuels.
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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) | 0.002 | 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".