The low-pressure cylinders of large units have the following characteristics:
The exhaust volume flow of the low-pressure cylinder is large, and the exhaust cylinder is required to be large in size. Therefore, a welded steel plate structure is generally used instead of the cast structure.
Generally, the inlet steam temperature of the low-pressure cylinder of the reheating unit exceeds 230 ° C, and the difference between the temperature and the exhaust steam temperature is 200 ° C. Therefore, a double-layer structure is also adopted. The flow part is subjected to temperature changes in the inner cylinder. The low-pressure inner cylinder is cast with high-strength cast iron, and the entire low-pressure outer cylinder that doubles as the exhaust cylinder is still welded. The huge exhaust cylinder only bears the exhaust temperature, and the temperature difference changes little.
⑶ In order to prevent the long-term no-load operation, the exhaust cylinder is deformed due to the excessively high exhaust temperature, a water spray cooling device is also installed in the exhaust cylinder.
⑷ In order to reduce the exhaust loss, the exhaust cylinder is designed as a radial expansion structure.