Abstract:
Aircraft are thought to contribute about 3.5% (IPCC, 1999) to the total radiative
forcing (a measure of change in climate) of all the human activities and this figure
is forecaste to increase. Future concerns for aviation’s role in climate change are
mainly due to the envisaged continued growth in this sector. Growth rates for
emissions are less than those for traffic growth since fuel efficiency continues to
improve over the years. Despite regular improvements in fuel efficiency, emissions
will carry on increasing and several solutions need to be found.
The growth of air travel as well and its effect on world economics is hampered by
local opposition to aircraft noise. Besides, restrictions on night take-off and landing
because of aircraft noise levels leads to a negative impact on the revenues of
Europe’s airlines and often results in non-European over-night airport refuelling
stops.
According to ACARE (Strategic Research Agenda, 2005), the sustainable
development of air transport depends on achieving a significant across-the-board
reduction in environmental impact, in terms of greenhouse gases, local pollution
and noise around airports. Over the past 40 years the introduction of new
technology has mitigated the environmental impact of aviation growth, but at the
expense of increasing operating costs. Consequently, in order to make aviation
more sustainable environmentally and economically, radically innovative turbofans
need to be considered and optimised at the aircraft level. Based on the above, this PhD project addresses the following research questions:
• The potential of different novel propulsion systems with enhanced
propulsive efficiency (using advanced, contra-rotating and geared
turbofans) and thermal efficiency (using intercooled and recuperated, and
constant volume combustion turbofans) to meet future environmental and
economical goals.
• The trade-offs to be made between noise, emissions, operating cost, fuel
burn and performance using single- and multi-objective optimisation case
study.
In order to achieve this, a multidisciplinary design framework was developed which
is made up of: aircraft and engine performance, weight, cost, noise, emissions,
environment, and economics and risk models. An appropriate commercially
available optimiser is coupled with this framework in order to generate a powerful
aero-engine preliminary design tool.
The innovative turbofans were benchmarked against the baseline turbofan at the
aircraft level using the A320. The multi-objective trade case study for minimum fuel
burn, NOx emissions, engine direct operating cost (DOC) and noise proves that
these engines are feasible to meet future noise and emissions requirements for an
acceptable cost of ownership. The key driver to lower engine DOC is a
considerable fall in fuel consumption. Nevertheless, acquisition and maintenance
cost rise owing to hardware complexity. Consequently, further study of these
engines is recommended as their environmental performance potential is
considerable.