TURBINE AIRFOIL AEROTHERMAL CHARACTERISTICS IN FUTURE COAL-GAS BASED POWER GENERATION SYSTEMS

摘要

Most promising operating cycles being developed for future coal-gas based systems are hydrogen-fired cycle and oxy-fuel cycle. Both cycles will likely have turbine working fluids significantly different from that of conventional air-based gas turbines. The oxyfuel cycle, with steam and CO_2 as primary working fluid in the turbine section, will have a turbine inlet temperature target at approximately 1750 C, significantly higher than the current level of utility turbine systems. Described in this paper is a CFD-based simulation on the transport phenomena around the gas side of a turbine airfoil under realistic operating conditions of future coal-gas based systems. The relatively high concentration of steam in the oxy-fuel turbine leads to approximately 40% higher heat transfer coefficient on the airfoil external surface than its hydrogen-fired counterpart. This suggests that advances in cooling technology and thermal barrier coatings (TBC) are critical for the developments of future coal-based turbine systems. To further explore this issue, a comparative study on the internal cooling effectiveness between a double-wall or skin cooled arrangement and an equivalent serpentine-cooled configuration is performed. The contribution of thermal barrier coatings (TBC) toward overall thermal protection for turbine airfoil cooled under these two different cooling configurations is also evaluated.