Aircraft Turbine Engine NOx Emission Abatement

Abstract

Extensive efforts are currently underway to develop combustors with lower nitrogen oxides (NOx) emissions for use in both subsonic and supersonic civil aircraft engines. Basically, NOx abatement of any significance requires means of reducing the peak flame temperatures within the combustor. To obtain these flame temperature reductions, while also maintaining acceptable combustor performance and operability at low engine power conditions, combustion process staging methods are needed. For use in advanced subsonic aircraft engines, combustors with leaner primary combustion zone fuel/air mixtures, together with combustion process staging features, are being developed. Significant NOx level reductions have been demonstrated with these advanced combustor design concepts. Although the resulting combustors are more complex than current technology combustors, satisfactory performance and operability appear attainable with these configurations. The initial introduction of these combustors into operational engines during the latter part of this decade is a likely prospect. In the case of advanced supersonic transport aircraft engines, combustors with ultralow NOx levels will probably be needed to prevent adverse impacts on the stratospheric ozone layer. For these engine applications, the use of very advanced and complex combustor design concepts is being investigated. One important element of these efforts is the development of technology for the suppression of the high-amplitude pressure oscillations typically associated with lean fuel/air mixture combustion processes.