Performance improvement of low-pressure cylinder in high back pressure steam turbine for direct heating

Abstract

Abstract It is the general retrofit to remove the last stages in the low-pressure cylinder of steam turbine for high back pressure direct heating, which can avoid the exergy loss caused by the traditional extracting steam heating mode of combined heat and power. However, the flow field of low-pressure cylinder will change. In this study, the last stage flow field of low pressure cylinder of such high back pressure turbine, as well as the temperature distribution, is analyzed and optimized by setting the diversion ring. Low-pressure cylinder of the 300MW steam turbine is selected as the research object. The optimal scheme is obtained after analyzing vortex distribution, static pressure recover coefficient and total pressure loss coefficient in flow field under different heating conditions. The results show that adding appropriate diversion ring bringing about vortex effectively reduced, leading to a sharp increase of 7.84% in efficiency of low-pressure cylinder and 0.63in statistic pressure recover efficient. It is also contributing to an apparently decrease of 0.95 in total pressure loss efficient. All results indicate that the aerodynamic performance of low-pressure cylinder has obvious promotion. Under high back pressure heating condition, the structure of low-pressure cylinder of steam turbine changed.