Combustion behavior study and flame zone analysis of biogas-fueled gas turbine combustor under O2/CO2 and O2/H2O oxidizing modes

Abstract

Environmental problems resulting from the increment of greenhouse gases have raised the tendency toward using renewable energy sources alongside carbon-capturing technology via oxyfuel combustion. In this regard, numerical simulation on the feasibility of using renewable biogas in the gas turbine combustor under two combustion modes, namely, O2/CO2 and O2/H2O, at high operating pressure is investigated in the current research. Considering that conventional air-based combustion systems are not suitable for oxyfuel combustion regimes, the modification of the gas turbine combustor will be addressed to provide the necessary conditions for proper operation at higher power densities on an industrial scale. In this study, the focus is on investigating the influences of the primary diluent mass flow rate ratio (PDR) and the O2 content in the oxidizer composition on combustion and thermal behaviors of biogas flame such as distribution of reaction zone and temperature, combustion species, pattern factor, combustion efficiency, CO pollutant emission, and as well as flame stability in different combustion modes. The results indicated that the PDR parameter plays an essential role in the combustion stability within the gas turbine combustor due to its direct exposure to the vortices created in the recirculation zone. Moreover, combustion instabilities were observed for biogas flame at PDR = 15% in both combustion modes and in O2/H2O case at PDR < 25%. It was also found that CO emissions decrease significantly with increasing PDR, so in higher PDR values, CO pollutant levels were observed at 39 ppm and 21 ppm in O2/CO2 and O2/H2O cases, respectively.