Experimental and numerical studies of premixed methane‐hydrogen/air mixtures flame propagation in closed duct
Bibliographic record
Abstract
Abstract In order to reveal flame propagation behaviour and the mechanism of premixed methane‐hydrogen/air mixtures (PMHAM), a pressure recording device was used for testing explosion pressure with different volume fractions of methane‐hydrogen in a closed duct. Results showed that the explosion pressure and pressure rise rate increased with volume fraction up to an optimum fraction of 10 % for a maximum explosion pressure (Pmax) of 0.60 MPa and a pressure rise rate ((dP/dt)max) of 54.93 MPa/s. Meanwhile, a high‐speed video camera was used for testing flame propagation behaviour with the optimum fraction. Results showed that the flame propagation process consisted four dynamic stages—spherical flame, finger‐shape flame, flame touching sidewalls, and tulip flame. Comparison of the numerical and experimental results showed reasonable qualitative and quantitative agreement. Additionally, the numerical simulation was used for addressing technical difficulties of understanding the mechanism of flame propagation. The simulated results confirmed the existence of two large‐scale vortices nearby sidewalls generated by the gas‐flow reflection and back‐streaming; these increased vortices made speed of the flame front touching sidewalls exceed that of the middle, which ultimately resulted in reversal of flame front. This meant that the interactions of gas‐flow reflection, back‐streaming, and vortex motions were the immediate reason of tulip flame.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 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 | 0.001 |
| 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".