Commercial aviation and air traffic is still expected to grow by 4-5% annually in the
future and thus the effect of aircraft operation on the environment and its
consequences for the climate change is a major concern for all parties involved in the
aviation industry. One important aspect of aircraft engine operation is the
performance degradation of such engines over their lifetime while another aspect
involves the aircraft flight trajectory itself. Therefore, the first aim of this work is to
evaluate and quantify the effect of engine performance degradation on the overall
aircraft flight mission and hence quantify the impact on the environment with regards
to the following two objectives: fuel burned and NOxemissions. The second part of this
study then aims at identifying the potential for optimised aircraft flight trajectories
with respect to those two objectives.
A typical two-spool high bypass ratio turbofan engine in three thrust variants (low,
medium and high) and a typical narrow body single-aisle aircraft similar to the A320
series were modelled as a basis for this study. In addition, an existing emissions
predictions model has been adapted for the three engine variants. Detailed parametric
and off-design analyses were carried out to define and validate the performance of the
aircraft, engine and emissions models. The obtained results from a short and medium
range flight missions study showed that engine degradation and engine take-off thrust
reduction significantly affect total mission fuel burn and total mission NOx emissions
(including take-off) generated. A 2% degradation of compressor, combustor and
turbine component parameters caused an increase in total mission fuel burn of up to
5.3% and an increase in NOx emissions of up to 5.9% depending on the particular
mission and aircraft. However, take-off thrust reduction led to a decrease in NOx
emissions of up to 41% at the expense of an increase in take-off distance of up to 12%.
Subsequently, a basic multi-disciplinary aircraft trajectory optimisation framework was
developed and employed to analyse short and medium range flight trajectories using
one aircraft and engine configuration. Two different optimisation case studies were
performed: (1) fuel burned vs. flight time and (2) fuel burned vs. NOx emitted. The
results from a short range flight mission suggested a trade-off between fuel burned
versus flight time and showed a fuel burn reduction of 3.0% or a reduction in flight
time of 6.7% when compared to a “non-optimised” trajectory. Whereas the
optimisation of fuel burn versus NOx emissions revealed those objectives to be non-
conflicting. The medium range mission showed similar results with fuel burn
reductions of 1.8% or flight time reductions of 7.7% when compared to a “non-
optimised” trajectory. Accordingly, non-conflicting solutions for fuel burn versus NOx
emissions have been achieved. Based on the assumptions introduced for the trajectory
optimisation analyses, the identified optimised trajectories represent possible
solutions with the potential to reduce the environmental impact.
In order to increase the simulation quality in the future and to provide more
comprehensive results, a refinement and extension of the framework also with
additional models taking into account engine life, noise, weather or operational
procedures, is required. This will then also allow the assessment of the implications for
airline operators in terms of Direct Operating Costs (DOC). In addition, the degree of
optimisation could be improved by increasing the number and type of optimisation
variables.
| Identifer | oai:union.ndltd.org:CRANFIELD1/oai:dspace.lib.cranfield.ac.uk:1826/9156 |
| Date | 05 1900 |
| Creators | Venediger, Benjamin |
| Contributors | Sethi, Vishal |
| Publisher | Cranfield University |
| Source Sets | CRANFIELD1 |
| Language | English |
| Detected Language | English |
| Type | Thesis or dissertation, Masters, MSc by Research |
| Rights | © Cranfield University 2013. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright owner. |
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