Influence of engine performance on emission characteristics

Abstract

This paper concentrates on the results of different investigations on aircraft engine emissions. In a first step semi-empirical emission correlation methods to predict the sum of nitric oxide and nitrogen dioxide (NO x ), carbon monoxide (CO), hydrocarbons (HC) and soot are introduced. They all are of a ariable reference type meaning, that published sea level static (SLS) measurements will be used as a reference. To calculate the amount of emissions for altitude operating conditions, the actual parameters involved like the fuel flow (for the NO x correlation method), the reciprocal value of the combustor loading parameter (for the CO and HC correlation methods) and the combustor inlet temperature and pressure, the flame temperature and the equivalence ratio (for the soot correlation method) are set into relation to the respective reference ground values. The necessary internal engine parameters are received from a thermodynamic engine modelling program shortly described in this paper. Because of the fact, that the engine thermodynamic state is mainly determined by the thrust demand of the aircraft and the ambient conditions, not only engines, but also aircraft engine combinations on different flight missions had to be looked at. Therefore a flight performance module is presented, which allows - - in combination with the engine modelling program and the emission calculation methods -detailed simulations and investigations of flight missions on the entire route. As a result not only the effects of engine performance modes and parameters (like bypass ratio in combination with overall pressure ratio) but also the effects of ambient conditions (like wind and ambient temperature) and flight profile (like cruise altitude, step climb, take off weight and payload factor) on the fuel burned and the emissions produced by different engines and aircraft in use are investigated. Finally the results of a comparison between a subsonic and a supersonic mission and a comparison between a jet aircraft of the first generation and a modern type are given.