The improvement of efficiency has been one of the most significant aspects of the development and application of steam turbines, along with the improvement of reliability and gains in both reduced maintenance and extended operation. There is now extra emphasis on evolving increased efficiency, because of the environmental need to reduce the problem of carbon dioxide. On the other hand, a lot of the existing steam turbines which were designed and manufactured based on conventional production technologies of those days are now still operating, and the most units have been utilized for more than ten or twenty years, because recently the construction of new power generation plants has been restricted. And furthermore, in some aging existing steam turbines, the decreased performance, efficiency and availability have been discovered due to time deterioration of the turbine parts and components. Under these circumstances, upgrading and life extension for the performance and reliability of steam turbines is required particularly for the existing ones. This paper describes the recent development and application of advanced steam path design, such as nozzles and blades for improving performance and reliability, that is, the upgrading and life extension of existing steam turbines as well as new projects. And also it describes a repowering system for existing power plants using gas turbines. These components and technologies are applicable to both new and retrofitted units.
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