Reduction of emissions by using various syngases with different injection strategies under premixed combustion mode

Increasing interest in alternative fuels for gas turbines has motivated research in gaseous fuels other than natural gas. Methane enriched with hydrogen or diluted with carbon dioxide are of considerable interest. The latter seems quite relevant for development of technologies such as oxyfuel combustion for carbon capture and storage in order to control temperatures in the combustion chamber. Thus, this paper presents an experimental study on the combustion of methane-carbon dioxide mixtures at atmospheric conditions. Gas mixtures have been examined by using different levels of premixing with different injection strategies with and without swirl and with and without central injection. A 20 kW burner has been used to investigate the flame stability and emissions performance by using these blends to examine the effect of CO2 addition. The burner configuration consisted of a centre body with an annular, premixed gas/air jet introduced through five, 60° swirl vanes. A TESTO 350XL gas analyzer was used to obtain NOx and CO emission trends to characterize all the injection regimes whilst using different fuel blends. CH chemiluminescence diagnostics was also used and correlated to the levels of emissions produced during the trials. The resulting images were analysed using Photron FASTCAM PFV ver 2.4.1.1 software and MATLAB R2015a. CO2 dilution decreased flame stability and operability range. The introduction of CO2 reduces temperatures in the combustion zone thus causing a reduction in emissions of nitrous oxides across all equivalence ratios. CO emissions also decreased with a limited (15%) CO2 addition. In terms of injection regimes, the outer purely premixed injection regime has lower NOx and CO, as expected. CH chemiluminescence distribution indicated that pure methane with central injection produced high fluctuation in CH production. The use of central premixed injection produces the most chaotic CH production case, possibly as a consequence of production of radicals in the central recirculation zone.