ICONE19-43289 EFFECTS OF FLOW LOSSES ON EFFICIENCY OF HTGR GAS TURBINE CYCLE

Abstract

High temperature gas-cooled reactor coupled with helium turbine cycle (HTGR-GT), based on the closed Brayton cycle, can take advantage of high temperature and achieve the high efficiency in power generation. The typical power conversion unit (PCU) of HTGR-GT is the vertical, single-shaft and compact configuration. All components of HTGR-GT are housed in pressure vessel, connected each other by pipes and irregular flow channels. Therefore the flow losses, including pressure drops and leakages inside pressure vessel, are unavoidable in actual projects and had significant influence on cycle efficiency. This paper presented a dimensionless model to analyze the effects of flow losses on cycle's features. (1) The effects of pressure drops: It showed that the pressure drop ratios of different components were inherently connected by Reynolds number due to the closed cycle. And the effectiveness of the heat exchangers can also be linked with the pressure drop ratios by Reynolds number. So the cycle's efficiency just depends on the effectiveness of recuperator and compression ratio, and there exists optimal recuperator's effectiveness and maximum cycle's efficiency. (2) The effects of pressure drops and leakages: leakages inside the pressure vessel could be divided into two groups by the seal's structure. It is found that leakage ratio could be connected to pressure drop ratios, seal's structure and other thermodynamic parameters. Therefore, the cycle's efficiency can also be expressed as the complex function of the effectiveness of recuperator and compression ratio, and leakages significantly reduce the cycle's efficiency. In brief, flow losses pose the limitation of cycle's efficiency for engineering design of HTGR-GT projects.