Experimental study of biogas combustion and emissions for a micro gas turbine

Biogas is a byproduct from the decomposition of organic matter and consists primarily of CH4, CO2 and N-2. Combustion of biogas in land-based gas turbines for power generation is a promising approach to reducing greenhouse gases and dependence on fossil fuels. The focus of this research was to investigate the effects of fuel compositions, fuel injectors position and pilot split on combustion performance on a DLE combustor designed for a micro-gas turbine. The lean ignition and extinction performance were tested for different fuel composition in an atmospheric condition, the combustion performance were tested in the engine working condition. For the combustion performance test, the emissions of CO and NOx were the main focus of the combustion products. The results showed a noticeable benefit of the reduction in NOx emissions with the reduction of fuel Wobbe Index (WI). The combustor also shows good combustion characteristics considering pollutant emission for the 50%-100% engine load as the fuel WI is besides the designed range. Mixing distance, jet direction and jet depth of fuel have significant effect on the reduction of NOx emissions since the increase of the mixing distance, fuel momentum and jet depth are conducive to improving the mixing uniformity of fuel and air. Pilot split has a significant impact on NOx emissions, the NOx emission has a lowest value for a certain pilot split. The experimental testing results confirmed the feasibility of the utilizing the biogas as an alternative fuel for the micro gas turbine, the results also provide general guidance for the challenge of micro gas turbine burner design for fuel flexibility.