Regional and Business Aircraft Mission Emissions

Abstract

To meet the design requirements of next generation aircraft engines and the expected trends of more stringent emissions regulations, better calculation methods for aircraft mission emissions need to be established. In the present investigation, a number of steps were taken to define an appropriate calculation technique. The data obtained for a full-scale annular combustor rig were compared with engine emissions to illustrate that the level of rig-to-engine agreement was good enough to use the rig data to formulate a proposed mission NOx calculation technique. Conventional methods were then used to correlate the rig data in terms of various operating parameters. It was demonstrated that the level of agreement with data was improved by including both combustion and geometrical aspects in the correlations of NOx, CO, UHC, and smoke. A semianalytical approach, which was based on detailed chemical kinetic scheme and simulated the combustor by a number of reactors representing various combustion zones, was used to correlate the data of the annular combustor. The results illustrated that better estimates of emissions were obtained over conventional methods. Two mission profiles that represented the operation of turbofan-powered regional and business aircrafts were selected to evaluate their mission emissions using the semianalytical method. An approach that utilized only the four ICAO test points in the semianalytical method was formulated to provide the total aircraft mission emissions. Results obtained by this approach were comparable to those calculated using correlations based on extensive testing of the combustor; thus, by using such a method considerable savings in cost and effort could be achieved during combustor development. The results also demonstrated the possibility of correlating the emissions in terms of ambient pressure and temperature and fuel flow rate; thus, accurate estimates of altitude emissions could be obtained.

Predictions of NOx Formation Under Combined Droplet and Partially Premixed Reaction of Diffusion Flame Combustors

“…The calculations utilized a detailed chemical kinetic mechanism to provide the trends of variation of pollutant formation with operating parameters. The developed calculation method was employed by Rizk and Smith (1994) to propose an effective means of establishing the engine emissions characteristics over the entire flight envelope using a limited number of tests. The approach utilized only the four power points defined by the International Civil Aviation Organization (ICAO) to provide the total aircraft mission emissions.…”