Investigation of A Low Emission Liquid Fueled Reverse-Cross-Flow Combustor

The investigated combustor employs injection of liquid fuel (ethanol) into the strong cross-flow of air using a round tube to achieve effective fuel atomization in non-premixed mode of operation. The reverse-flow configuration (air injection from the exit end) allows effective internal product gas recirculation and stabilization of the reaction zone. This apparently suppresses near-stoichiometric reactions and hot spot regions resulting in low pollutant (NO_x and CO) emissions in the non-premixed mode. The combustor was tested at thermal intensity variation from 19 to 39 MW/m³ atm with direct injection (DI) of liquid fuel in cross-flow of air injection with two fuel injection diameters of 0.5 mm (D1) and 0.8 mm (D2). The combustion process was found to be stable with NO_x emissions of 8 ppm (for D1) and 9 ppm (for D2), the CO emissions were 90 ppm for D1 and 120 ppm for D2, at an equivalence ratio (ϕ) of 0.7. Macroscopic spray properties of the fuel jet in cross-flow were investigated using high-speed imaging techniques in unconfined and nonreacting conditions. It was found that the fuel jet in smaller fuel injection diameter (D1) case penetrated farther than that in D2 case due to higher fuel injection momentum, thus possibly resulting in a finer spray and better fuel-oxidizer mixing, and in turn leading to lower CO and NO_x emissions in the D1 case as compared with the D2 case.