期刊名称：Bulletin of the Institute of Heat Engineering
印刷版ISSN：2083-4187
出版年度：2019
卷号：99
期号：1
页码：10-14
出版社：Warsaw University of Technology
摘要：Most thermal and nuclear power plants use a steam turbine to convert steam potential energy into mechanical work on the rotating rotor. To operate the steam turbine at high efficiency, the aerodynamic losses in the flow path must be decreased, especially in a low-pressure turbine (LPT). This study focuses on the problem of flow separation in the area of the external contour, occurring at high expansion angles of the flow path and constituting a principal cause of flow non-uniformity upstream of the nozzle assembly. Under specific flow conditions, the nozzle assembly peripheral area can be blocked by concentrated vortex, resulting in a sharp increase in losses. A numerical study and comparative analysis of two solutions to this problem were conducted. Quantitative evaluation of nozzle blade cascade energy loss reduction showed that the flow suction on the external surface of a wide-angle diffuser is the most effective in the case of removal of 2% of total flow, using holes located in the middle of an annular diffuser. In this case, the loss coefficient of nozzle blade cascade was reduced by 2.1%. Enhancement of LPT flow path, by mounting an aerodynamic deflector in a wide-angle diffuser, led to a 3% decrease in the loss coefficient. The research results lead to the conclusion that energy losses caused by high expansion angles of LPT flow path can be reduced by applying the considered methods to prevent flow separation on the external contour upstream of the nozzle assembly.
