Compatibility Between Low-NOx Emissions and High–Combustion Efficiency by Lean Direct Injection Combustion

Abstract

This paper describes the low–emissions capability of lean direct injection, liquid–fueled burners for gas turbine combustors. The emissions characteristics of direct injection and premixed–prevaporized combustion systems were evaluated at inlet air temperatures of 450, 550 and 650 K and at atmospheric pressure. The equivalence ratio was varied in a range from about 1.2 to values close to flammability limits. The effects of fuel nozzle capacity and mixing tube length were also investigated. In the direct injection system, a double swirler/fuel nozzle module was used to inject fuel spray and air into combustion chamber. Fuel was atomized into the circular swirling jet using a pressure fuel nozzle placed 15 mm upstream of the inner swirler channel exit. In the lean premixed–prevaporized combustion system, the same double swirler/fuel nozzle module was used also for fuel–air mixing and a tube was inserted between the double swirler/fuel nozzle module and the end wall of the combustor chamber for fuel prevaporization. At lean conditions, combustion was more complete for the direct injection combustion system than premixed–prevaporized combustion system, though both were capable of very low NOx emissions.