Dynamic response of a rotating structure during start and stopsequences
Bibliographic record
Abstract
With the advent of new renewable energy sources, such as wind and solar, hydraulic turbines that usually operated at the best efficient point in the past, are now undergoing more and more start and stop sequences.Many studies focusing on Francis turbines have shown that significant mechanical stress can be induced during these start and stop sequences.The rotor-stator interaction (RSI) is one of the main excitations that can cause significant mechanical stress if, for instance, one of the natural modes of the runner is excited.In fact, when the angular velocity of the runner increases during the start-up, the runner is excited by the RSI which then corresponds to a sweep excitation.To our knowledge, the exact conditions that lead to significant stress during the speed variation of the runner, during start and stop sequences, are still not well known.An experimental set-up was designed to investigate the mechanical behaviour of a rotating structure under RSI excitation during speed variations.The rotating structure is similar to a Francis runner and was designed, with the help of FEA, to be specifically excited by the RSI fundamental frequency and its second harmonic.To simplify the structure for CFD simulation purposes, seven rods mimicking traditional runner blades were used.Considering the particular design of the rotating structure, a flow straightener was also designed to prevent a large backflow near the structure and high swirl in the draft tube.The rotating structure is driven by a 3hp AC electric motor that controls the acceleration rate with a variable frequency drive.A total of 14 strain gages located on the rods and the band are used to measure the vibration of the rotating structure.
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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".