On the topic of CO_2 capture from gas turbines, exhaust gas recirculation (EGR) is a commonly discussed method to increase CO_2 concentration at a gas turbine outlet to make the CO_2 capture process more efficient. This paper presents the influence of the recirculation on heat release rate and emissions. The investigation is made using the commercial RANS solver ANSYS CFX coupled with an in-house code for a hybrid transported PDF/RANS simulation using detailed chemistry of GRI 3.0. Initially an investigation on reactivity was made using numerical calculation of laminar flame speed. It is found that exhaust gas recirculation has only a minor effect on reactivity in lean premixed combustion. Therefore, the operation point of the combustor can be kept constant with and without EGR. Simulations of the combustor with exhaust gas recirculation using the hybrid PDF/RANS with GRI 3.0 show a minor influence of NO and NO_2 doping of the vitiated air on the flame speed and the doping delays heat release slightly. CO doping has no effect on heat release rate. CO emissions at combustor exit remain unaffected by NO, CO or NO_2 doping. Seeding the vitiated air with 50ppm nitric oxides reveal that any NO_2 present in the vitiated air is reduced to NO in the flame. NO_2 emissions increase with NO_2 doping but are still 2 magnitudes lower than NO emissions. It is found that NO is reduced by 3% due to of NO reburn. Based on literature data it is concluded that there is a deficit of the GRI 3.0 reaction mechanism. Experimental data taken from literature reveal of NO reburn by approximately 20%. Therefore emission data of nitric oxides of flames that should show a considerable reburn effect should be used with caution, while heat release and CO emissions are predicted more accurately. It is shown, that with the model created for the generic gas turbine combustor it is possible to study the effects of exhaust gas recirculation on the combustion process in detail and resolve detailed kinetic effects.
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