The Tip Clearance Flow Resonance Behind Axial Compressor Nonsynchronous Vibration
Bibliographic record
Abstract
Nonsynchronous vibration (NSV) is a particular type of aero-elastic phenomenon, where the rotor blades vibrate at nonintegral multiples of the shaft rotational frequencies. NSV behavior appears similar to off-design stall flutter but with a particular blade tip flow evolution. This paper demonstrates the link between NSV and the resonance induced by the tip clearance flow based on a proposed hypothesis and experimental confirmation. At off-design operating conditions, the rotor blade tip clearance shear layer flow can evolve tangentially. It is proposed that this tangential flow becomes a support for an acoustic feedback wave that settles between rotor blades. The feedback wave is driven by the blade vibratory motion and synchronizes the shear layer vortical structures with the blade vibration frequency. Depending on the blade tip local temperature, and when the feedback wavelength matches within one or two blade pitches, the system becomes resonant and very high vibrations can occur on the blade. An axial stage compressor test rig is set-up to look into the underlying mechanism behind NSV through targeted measurements using both static and rotating instrumentation. The experimental apparatus consists of the first stage of a high pressure compressor driven by an electric motor. The test-section is built to minimize the effects of the adjacent stator blade rows in order to isolate the role of rotor blade tip clearance flow on NSV. Sensitivity studies are carried out to assess and demonstrate the effects of the rotor blade tip clearance and inlet temperature on NSV and validate the predicted resonance for NSV occurrence under various conditions. Vibrations and surface pressure data from adjacent blades are collected to demonstrate the predicted interactions between neighboring rotor blades. Finally, evidence of the staging phenomenon, inherent to the proposed NSV mechanism, is experimentally obtained. All the data obtained are consistent with and thus in support of the proposed mechanism for NSV.
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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".