This study deals with an experimental investigation of a low emission liquid fuelled (ethanol) reverse cross-flow combustor. This investigation is carried out to cater to the need of burning liquid fuels (including alternative fuels) with minimum emissions in gas turbine engines used for both aircraft and land based power generation applications using modern combustion technologies. In the present combustor design, the air inlet and the exhaust ports are located on the same side (and hence the name reverse-flow) whereas the liquid fuel is injected directly into the strong cross-flow of the air using a small diameter round tube to aid fuel atomization. Hence, a conventional atomization system is absent in the investigated combustor. The reverse-flow configuration allows effective internal product gas recirculation to facilitate the preheating and dilution of the oxidizer stream and stabilization of a distributed reaction zone. This apparently suppresses near stoichiometric reactions and hot spot regions resulting in low pollutant (NOx and CO) emissions. In the present case, the heat load is varied (keeping a constant air flow rate) from 3.125 kW to 6.25 kW which results in the thermal intensity variation from 19 MW/m3-atm to 39 MW/m3-atm. Two different tubes with internal diameters (dfuel) of 0.5 mm and 0.8 mm are used for injection of liquid fuel into the cross flow of air. The combustor was also tested in premixed-prevaporized (PP) mode with ethanol for benchmarking. The combustion process was found to be stable with NOx emissions of 1.6 ppm (premixed-prevaporized), 8 ppm (dfuel = 0.5 mm), 9 ppm (dfuel = 0.8 mm). The CO emissions were 5 ppm (premixed-prevaporized), ∼100 ppm (dfuel = 0.5, 0.8 mm), at atmospheric pressure operation (corrected to 15% O2) and ϕ = 0.7, Tadiabatic ∼1830 K. Reaction zone positioning inside the combustor was investigated using OH* chemiluminescence imaging and global flame pictures, and the same was found to be located in the vicinity of the air jet.
A Combustion Process Optimization and Numerical Analysis for the Low Emission Operation of Pulverized Coal-Fired Boiler