Abstract
A new type of closed-cycle gas turbine which uses supercritical carbon-dioxide (SC-CO_2) as a working fluid was proposed and has been studied in these days. It is supposed that the behavior of SC-CO_2 will be different from that of perfect gas because the thermal properties of SC-CO_2 will change dramatically according to the slight changes of temperature or pressure in compressors. Analysis of the flow field in compressors is needed in order to operate compressors stably and to design blades optimally. In this paper, two-dimensional nozzle flow was simulated in order to confirm that the scheme can analyze the behavior of SC-CO_2 stably. Then the flow field of SC-CO_2 in a centrifugal compressor was simulated under several conditions. As a result, entropy generation was noticeable near the vortex induced by the tip leakage flow and this caused pressure loss. So it is assumed that pressure loss leads to the dynamic changes of thermal properties and to the shift to the low-density fluid locally.
