NUMERICAL STUDY OF RADIATION HEAT TRANSFER FOR A SUPERCRITICAL CO_2 TURBINE LINEAR CASCADE

摘要

The fundamental research and technology development for supercritical CO_2 (sCO_2) power cycles is gaining worldwide popularity. This is due to their promise of high efficiency, compactness, wide-range-applicability and eco-friendliness. One of the active research areas in the sCO_2 power cycle field is to increase cycle efficiency by utilizing a higher turbine inlet temperature. At high temperatures within turbines, radiation may contribute a significant portion of overall heat transfer. The purpose of this paper is to investigate and quantify the effects of radiation heat transfer within a first stage sCO_2 turbine linear cascade. This particular topic has not been explored by researchers yet. The correct estimation of radiation heat transfer can prove to be critical for the design of turbine blade cooling system. The aerodynamic and heat transfer analysis of a turbine cascade is carried out using a commercial computational code, STAR-CCM+. Spectral absorption coefficient for CO_2 is derived using HITRAN database at required temperature and pressure. Broadening and shifting of intensity lines due to high pressure and temperature are taken into consideration. A second approach utilizes Planck mean absorption coefficient as a function of temperature. Although the data can be extrapolated for the required higher pressure, accuracy of that extrapolated data cannot be verified. Hence the secondary purpose of this study is to encourage researchers to fill the fundamental gaps in the knowledge of CO_2 radiation. Findings presented here suggest that radiation can be neglected for cooling system design of the sCO_2 turbine stage 1 vane for both inlet temperatures of 1350K and 1775K.