Advanced Large Steam Turbines for Saturated Steam Conditions

摘要

The nuclear option is increasingly considered in the energy strategy of more and more countriesrnin the world. The reasons are replacement of old nuclear power plants, reducing green house gasrnemissions demanded by the Kyoto Protocol and equal or lower overall cost of a nuclear plantrncompared to conventional plants.rnConcerning the primary part of the nuclear power plant efforts were undertaken to improvernpower output, efficiency and safety systems of the reactor. On the secondary side Siemens hasrnperformed an intensive development of the saturated steam turboset (SN product line). The mainrntasks are: a suitable turboset for high power output up to 1700 MWel, increased efficiency byrnmodern blade and turbine design and a design for lifetime of more than 40 years of operation.rnSiemens SN steam turbines have been proven for many years and millions of accumulatedrnoperation hours. Therefore the SN product line is the design basis for the improved developmentrnof advanced nuclear power plant turboset. The turboset consists of a double shell, double flowrnhigh pressure turbine which can handle main steam conditions up to 80 bar (870 psi) and morernthan 300℃ (572 °F). After moisture separation and reheating the steam enters two or threerndouble shell, double flow low-pressure turbine cylinders. The maximum total last stage exit arearnreaches a value of 150m~2. The low-pressure turbine rotor design is characterized by the wellprovenrnand steadily improved shrunk-on disk design. The overall length of the turbine includingrnthe generator is about 68 m. Due to the demand for the highest turbine efficiency Siemensrndevelopment for HP blading called 3DSTM was applied (3D Secondary losses reduced). Inrnaddition to that the LP turbines are designed with the longest freestanding last-stage blades tornminimize the exhaust losses. Measurements against corrosion and erosion are applied byrnadvanced high chromium materials, surface coatings and removal of water by suction slots inrnblades and drains in all extraction lines.