Simulations numériques d'essais expérimentaux de contact aube/carter
Bibliographic record
Abstract
Tightening environmental standards and rising fuel costs are driving engineers to design more efficient, greener aircraft engines. One preferred approach aims to minimize the functional clearance between the fixed and rotating parts of the engine. A higher compression ratio within the low-pressure compressor delivers superior aerodynamic performance. This is achieved by reducing the leakage flow at the blade tip interface. Closing the gap between said blades and the casing causes structural contacts to happen more frequently. These may lead to dangerous vibratory phenomena called rotor/stator interactions. These interactions, yet to be fully understood, combine mechanical contacts, nonlinear vibrations, thermomechanical effects and complex abradable wear mechanisms. The complexity of the latter raises the necessity to determine the origin and the characteristics of these interactions as well as their potential severity. The adoption of numerical tools to simulate vibratory blade behavior after contact is rising as an essential step during the design phase of the blades. Simulations could have the capability to prevent the worst cases of interactions by discriminating certain blade/abradable configurations depending on their propensity to lead to dangerous interactions. However, the efficiency of the numerical tool relies on a proper configuration beforehand. Hence, the calibration of those predictive tools requires the implementation of experimental and original test rigs to reproduce engine like operating conditions. Furthermore, those also help grasping a more complete comprehension of all phenomena involved throughout the interactions. In partnership with Safran Aero Booster, the objective of this master thesis is to calibrate Coros, the tool developed at the Laboratoire d’Analyse Vibratoire et Acoustique (LAVA) of Polytechnique Montreal, by replicating a critical blade/abradable contact scenario observed experimentally. Numerous simulations were performed and analyzed in order to refine the simulation parameters of the tool and to confirm its predictive utility. For the first time, a cutoff criterion, based on the yield stress of the tested blade, is integrated within the results analysis procedure. This new methodology gives us the means to delimit the validity scope of the numerical results evaluated by Coros. The set of parameters, adjusted using a reference test, are then applied to conduct the largest comparative analysis to date. A total of four experiments on four different industrial rotor blades are numerically reproduced using the same set of calibrated parameters. The experimental and numerical results come to agreement and allow us to consider qualitative criteria in order to rank blades relative to their capacity to withstand repetitive contact. For example, based on the predicted wear pattern or the number of angular velocities showing a rotor/stator interaction a blade reacting strongly at several different speeds would be deemed less robust than one with few critical velocities over the analyzed speed range
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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 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.002 | 0.001 |
| Insufficient payload (model declined to judge) | 0.007 | 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".