Abstract:
Though nitrogen oxides (NOx ) emissions from aircraft make a relatively small
contribution to the overall NOx emissions when compared to surface emissions, they
constitute the only man-made pollutant at high altitude. Excessive NOx emissions might
cause ozone depletion in the stratosphere and ozone increases in the troposphere, both
topics of increasing environment concern in recent years. To tackle the problem of NOx
emissions and their effects upon the environment, the spatial distribution of NOy (NOx +
RN03) needs to be fully understood.
The most significant source of NOx emissions is due to long range civil subsonic
aircraft during their cruise phase. Detailed studies were performed for seven cases,
including five single flight and two global scale scenarios, using the most widely used
B747-400 aircraft which are powered by 4 three-shaft turbofan engines. Using models
of aircraft performance, cruise phase NOx emissions are derived and employed as input
to run a three-dimensional chemistry transport model. In order to achieve realistic
results, all scenarios were carried out using a one-year period of simulation to study the
transport and dispersion of NOy emitted from aircraft exhausts. For a better
understanding of the atmospheric behaviour of NOy , two other cases were also carried
out, a one-month simulation during both summer and winter situations. The results
show that the upper troposphere may certainly be perturbed by aircraft NOx emissions at
cruise altitude. The relative increase in NOx concentration is estimated to be of the order
of 40% in the meridional average and up to 160% in regions covered with heavy air
traffic such as Europe, the USA and the North Atlantic.
This thesis investigates the quantity of long range civil subsonic aircraft NOx
pollutants at cruise altitude and their subsequent implications for the upper troposphere.
It discusses the concept of atmospheric NOy pollution chemistry, using computer
programs developed for both total aircraft performance and 3-D chemistry transport
modelling, and combinations thereof. Simulations have been conducted to predict the
relationship between the NOx emissions and the environment. In addition, the thesis
highlights the most important variables and derives a procedure to model the emissions
from subsonic aircraft flight and to assess their impacts upon the atmosphere. Finally,
some complicated problems which need further work are also mentioned.
