Gas-Side Heat Transfer in Syngas, Hydrogen-Fired and Oxy-Fuel Turbines

To meet the performance goals of advanced fossil power generation systems; e.g. FutureGen, future coal-gas fired turbines will need to be operated at temperatures higher than those in the current commercial natural gas-fired systems. The working fluid in these future turbines could contain substantial moisture (steam) mixed with carbon dioxide, instead of air or nitrogen in conventional gas turbines. As a result, the aero-thermal characteristics among these new turbines are expected to be significantly different not only from the natural gas turbines but also dependent strongly on the compositions of turbine working fluids. Described in this paper is a quantitative comparison of thermal load on the external surface of turbine airfoil present in different power cycles the US Department of Energy plans for the next decade. The study is pursued with a computational simulation based on three-dimensional computational fluid dynamics (CFD) analysis. While the heat transfer coefficient has shown to vary strongly along the surface of the airfoil, the projected trends were relatively comparable for airfoils in syngas and hydrogen-fired cycles. However, the heat transfer coefficient for the oxy-fuel cycle is found to be substantially higher, by about 50–60%, than its counterparts in syngas and hydrogen turbines. This is largely attributable to the high steam concentration in the turbine flow. This overall suggests that advances in cooling technology and thermal barrier coatings are critical for the developments of future coal-based turbine technologies with nearly zero emission.