Natural gas oxy-fuel cycles—Part 2: Heat transfer analysis of a gas turbine

The influence of the cycle conditions of Semi-Closed Oxy-Combustion Combined Cycles (SCOC-CC) onto the heat transfer to the 1st row turbine vane in gas turbines was investigated using empirical correlations for a cylinder in a cross flow and for a flat plate in a parallel flow being representative for the leading edge and for the vane span, respectively. Radiative heat transfer was modelled using absorptivities/emissivities describing the reduction of the thermal radiation absorption/emission by the hot combustion flue gas as compared to a black-body. The contribution of chemiluminescence was evaluated by means of numerical simulation using a detailed kinetic model of the combustion process extended for radiation processes. SCOC-CC with flue gas recirculation before condensation results in a 20–30% increase of heat transfer due to convection and thermal radiation as compared to SCOC-CC with flue gas recirculation after condensation. Further the increase of the pressure ratio from π=17 to π=40 at fixed thermal power and turbine inlet temperature results in an increase of both the convective and the radiative heat transfer of the order of 10%. Chemiluminescence did not have any influence on the heat transfer, because the powers emitted by excited OH- and CH-radicals were smaller than 10−8% of the thermal power.