499 / 2018-12-31 15:36:20

THE INFLUENCE OF SHAFT SEAL STEAM SUPPLY PARAMETERS ON HOLDING SHAFT PHENOMENON

steam turbine, seal steam, holding shaft

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With the rapid development of national economy, ultra-supercritical coal-fired steam turbine, as the representative of the high efficiency and energy saving power generation technology, have taken over an important portion in the global market. It is significant to ensure safe and stable operation of the units. However, the phenomenon of holding shaft often occurs during abnormal shut-down for several units. The preliminary analysis found that this phenomenon is due to the unit suffering the sudden cold or thermal shock, and then thermal expansion mismatch has been caused between the rotor and cylinder. Improper handling may cause serious influence on the following operation.
The operation data of several Ultra-supercritical turbine has been Investigated and analyzed at the time of gland seal shaft seizing, which revealed that lower gland steam temperature is the main reason for the accident of gland seal shaft seizing. A steady and transient FE model was generated to predict the temperature field and displacement under different seal steam temperature. Clearance variations between rotor and casing in gland sealing region during an actual sharp shutdown process was investigated by FE analysis. And then, operating data of a cold-start duration from a power plant was used to validate the thermal FE model. In conclusion, calculations and the accident data analysis based on different shaft seal steam temperature shows that the wear of the shaft sealing and holding shaft accidents are closely related to the switching temperature and speed of the shaft seal steam supply. This study also establish a base of future clearance design during turbine transient operation.