Analysis of concepts to reduce the environmental impact of aviation

Doctoral thesis, 2014

The average yearly increase in passenger kilometres travelled by air has been 5.8 % over the last 40 years. Fortunately the fuel consumption has not increased at the same rate. Over the same time period the average increase in fuel sold has been 2.2 % per year. However, if the growth of air traffic is going continue at the same pace, to minimise the climate effect, the rate of technological and operational improvement will have to increase. In this thesis some options on how to reduce the climate impact of aviation have been analysed. A number of engine concepts to increase propulsive efficiency have been evaluated. The studies include a comparison between a geared turbofan and a two shaft direct drive turbofan for a future single aisle aircraft. Results show that the geared turbofan engine has a potential to reach approximately 4 % lower fuel consumption than a direct drive configuration. Three options for the propulsion of a future regional aircraft have been analysed; an open rotor, an advanced turboprop and a turbofan engine. The specific range for this aircraft with varying Mach number for the three different engine options is shown. It is seen that the open rotor configuration combines low fuel consumption with the possibility of cruise Mach numbers normally associated with regional jets. The thesis also includes analysis of the effect on fuel consumption when flying to reduce formation of persistent contrails. Data from real transatlantic flights have been used in this evaluation and the results show a less than 0.4 % increase in fuel consumption while reducing contrail formation by approximately 50 %. The work has been carried out using a set of conceptual design tools to model engine performance, engine dimensions and weight, nacelle drag, aircraft performance and weight, as well as aircraft mission calculations. In the course of this work a number of sub models have been refined and some models have been added.