Low-NOx Combustor Development pursued within the scope of the Engine 3E German national research program in a cooperative effort among engine Manufacturer MTU,University of Karlsruhe and DLR German Aerospace Research Center

MTU Aero Engines, the University of Karlsruhe and the DLR Aerospace Research Centre co-operated within the scope of the German national aeronautical research program Engine 3E. The program was focused on improving high-bypass turbofan engines. As a part of this program, a low-emission single-annular combustor was developed. The NOx emissions of this combustor are significantly reduced by using the rich-lean combustion concept.The basic idea of this concept is to avoid stoichiometric combustion conditions by splitting the combustion domain into a fuel-rich zone (low-oxygen zone) and a fuel-lean (low temperature zone). The NOx reduction capability of a combustor of this type scales with the homogeneity of the mixture in the rich zone and the time interval needed for the transition from the rich to the lean zone.Based on the insights gained from this cooperative research, an annular combustor was developed and tested at pressures up to 20 bar and inlet temperatures up to 800 K. The tested annular combustor was found to have NOx emissions of about 40% of the ICAO 96 standard. The carbon monoxide and unburned hydrocarbon emissions of the combustor are of about the same levels as present state of the art combustors.