Near-Field Characteristics of a Rectangular Jet and Its Effect on the Liftoff of Turbulent Methane Flame
Bibliographic record
Abstract
Understanding the stability of turbulent flames is a key for the design of efficient combustion systems. The present paper reports an experimental study on the effect of the internal geometry of a rectangular orifice on the characteristics/stability of a turbulent methane flame. Three rectangular nozzles with different orifice lengths having an identical exit aspect ratio (AR) of 2 were used. The co-airflow strength was also varied to evaluate its effect on the jet flow emerging from the rectangular nozzle. The experimental data revealed that the jet initial conditions affect both the flow characteristics and the liftoff of turbulent diffusion methane flame. That is, increasing the orifice length of the rectangular nozzle resulted in delaying the occurrence of the axis-switching phenomenon, reducing the length of the jet potential core, and accelerating the liftoff transition of the attached flame. The co-airflow was found to reduce the velocity strain rate in the shear layer, displace the occurrence of axis-switching farther downstream of the jet, and delay flame detachment. The results revealed also that there is a clear interplay between the flame liftoff and the jet near-field molecular mixing and flow characteristics. That is, a rectangular jet which spreads faster and generates higher near-field velocity strain and turbulence intensity causes flame detachment at a lower fuel jet velocity. Based on this, a correlation was found between the flame liftoff velocity, the fuel molecular thermal diffusivity, the stoichiometric laminar flame speed, and the fuel jet strain rate at the nozzle exit. This relationship was shown to successfully predict the liftoff velocity of methane flame as well as other common gaseous hydrocarbons and hydrogen flames.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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) | 0.000 | 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 teacher head, 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".