Subjects and fundamental countermeasure on HTGR gas turbine

The present paper points out the difference of the helium closed cycle gas turbine, which is a candidate of nuclear gas turbine, from the open cycle gas turbine and indicates its inherent problems on pressure ratio and specific speed owing to the use of helium as the working gas. The paper also clarifies the effects of external pressure losses on the thermal efficiency and output of the gas turbine besides, it indicates that the major reason of the German unsuccessful helium turbine owes to deterioration of the external efficiencies of compressor and turbine resulted from pressure losses and the use of helium itself. Besides above, the paper indicates the key idea or? heat exchangers for the closed cycle gas turbine and design basis to solve the problems and finally offers new conception with nitrogen or air as the working gas that is changeable into open cycle gas turbine.