CO2 has a strong impact on both operability and emission behaviours in gas turbine\ncombustors. In the present study, an atmospheric, preheated, swirl-stabilised optical gas turbine\nmodel combustor rig was employed. The primary objectives were to analyse the influence of\nCO2 on the fundamental characteristics of combustion, lean blowout (LBO) limits, CO emission\nand flame structures. CO2 dilution effects were examined with three preheating temperatures\n(396.15, 431.15, and 466.15 K). The fundamental combustion characteristics were studied utilising\nchemical kinetic simulations. To study the influence of CO2 on the operational range of the combustor,\nequivalence ratio (�¦) was varied from stoichiometric conditions to the LBO limits. CO emissions were\nmeasured at the exit of the combustor using a water-cooled probe over the entire operational range.\nThe flame structures and locations were characterised by performing CH chemiluminescence imaging.\nThe inverse Abel transformation was used to analyse the CH distribution on the axisymmetric plane\nof the combustor. Chemical kinetic modelling indicated that the CO2 resulted in a lower reaction rate\ncompared with the CH4/air flame. Fundamental combustion properties such as laminar flame speed,\nignition delay time and blowout residence time were found to be affected by CO2. The experimental\nresults revealed that CO2 dilution resulted in a narrower operational range for the equivalence\nratio. It was also found that CO2 had a strong inhibiting effect on CO burnout, which led to a higher\nconcentration of CO in the combustion exhaust. CH chemiluminescence showed that the CO2 dilution\ndid not have a significant impact on the flame structure.
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