Thermal and Stress State of the Steam Turbine Control Valve Casing, with the Turbine Operation in the Stationary Modes
Bibliographic record
Abstract
The purpose of this paper is to determine the most stressful zones and assess the possibility of plastic deformations of the control valve casing in its crack forma-tion zones, with the K-325 steam turbine operation in the stationary modes. The problem is solved in two stages. First, the steam flow characteristics in the steam distribution system and the casing temperature are determined. Then, the elastic stress-strain state of the casing of one of the two valve units (through which the steam consumption is always greater than through the other) is esti-mated using the values of the casing temperature field. The characteristics of steam flow in the steam distribution system and the thermal state of the control valve casing are determined numerically by the finite element method. The steam flow rates, temperature and pressure on the casing wall are determined based on the solution to the Navier-Stokes equation in a three-dimensional for-mulation. It is established that the steam temperature before the turbine control valves is practically the same as the one before the stop valve. In the casing itself, after the control valves, with the valves partially open, a significant drop in steam temperature may occur due to throttling. A significant decrease in the steam temperature in the control valve (by 100 °C) is observed at low power with a nominal vapor pressure after the boiler. The calculation of the elastic stress-strain state of the control unit casing was carried out using the finite element method based on the three-dimensional mathematical model for casing deformation. As a result, the stress state of the valve casing was obtained for the different operating modes of the turbine. It is shown that differences in stresses for different modes are associated with changes in the thermal state of the valve casing and the distribution of pressure on its walls. Zones of possible plastic deformations of the valve casing are established. In those zones, the elastic stresses exceed the yield strength of the material. The obtained results clearly show that the most dangerous mode in terms of the control valve casing static strength is not the turbine nominal mode of operation at a power of 320 MW, but a part-load operation mode, at 180 MW.
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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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".