Experimental investigation of combustion instability in a centrally staged combustor under self-excited oscillation conditions
Bibliographic record
Abstract
This paper presents an experimental investigation of combustion instability and flame dynamics in a laboratory-scale lean premixed prevaporized centrally staged combustor under self-excited oscillations. The macrostructure of the flame is captured by CH* chemiluminescence images using a high-speed camera, and the two-dimensional flow field of the combustor center plane is obtained by using particle image velocimetry. The effects of the pilot stage swirl number and main stage equivalent ratio on the thermoacoustic oscillations and flame dynamics are analyzed. The results indicate that there are intermittent oscillations, limit cycle oscillations, and mode switching in the combustor. As the pilot stage swirl number increases, the system transitions from intermittent oscillation to limit cycle oscillation. Additionally, the case with a pilot stage swirl number of 0.5 also occurs mode switching. Based on dynamic mode decomposition, the heat release fluctuation is primarily concentrated in the shear layers under different operating conditions. Furthermore, the intensity of thermoacoustic oscillations in a system is determined by the coupling strength between pressure and heat release fluctuations. From the results of the flow field, it is observed that as the pilot stage swirl number increases, the time-averaged axial strain rates and vorticities increase, but the time-averaged axial velocity is generally lower for the swirl number of 0.7 compared to the other two cases. On the other hand, the time-averaged axial strain rates and vorticities for the case with a swirl number of 0.5 decrease with the increase in the main stage equivalence ratio before and after the mode switching.
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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 | 0.001 |
| 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".