Combustion and emission performance of CO2/CH4/biodiesel and CO2/CH4/diesel blends in a Swirl Burner Generator

Renewable biomass derived fuels are of increasing attention for industrial and aerospace applications due to worldwide depletion of fossil fuels and stricter environmental legislations. These facts have prompted continuous development for clean, sustainable and alternative fuels that produce low emissions. Even more, fuel flexibility is a required feature to meet all the former characteristics while reducing operating cost in gas turbines. Thus, some alternative fuels such as syngas or biodiesel can be used for gas turbines as these can comply with these requirements while being obtained from various processes, making them potential candidates for sustainable power generation. On the other hand in many combustion applications, the fuel is originally present as either liquid or solid. To assist mixing and the overall burning rate, the fuel is frequently first atomised and then sprayed into the combustion chamber. Most of the existing approaches dealing with combustion flows are limited to single-phase injection. To remove this limit, a new model for multiphase combustion has been developed. Therefore, this experimental work investigated the performance of a swirl burner using various mixtures of CO2/CH4 blends with either diesel or biodiesel derived from cooking oil. A 20 kW swirl burner was employed to analyse gas turbine combustion features under atmospheric conditions to quantify flame stability and emissions by using these fuels. A TESTO 350XL gas analyser was used to determine NOx and CO emission trends. Comparison between the blends was carried out at different equivalence ratios. CH* chemiluminescence diagnostics was also used and linked with the levels of emissions created through the trials. The results revealed that the use of biodiesel and CO2/CH4 blends mixtures resulted in lower CO production, i.e. 87% lower for the case at 10% CO2. Results showed that a notable reduction of ~50% in NOx was obtained at all conditions for the biodiesel /CO2/CH4 blends. Diesel based flames showed high CH* intensity at the axial profile compared to the biodiesel blends due to their high sooting tendency.