| Summary: | Gas turbine engine NOX, CO2 and H20 exhaust emissions from civil subsonic fleets are
potentially in sufficient amounts to affect atmospheric ozone and climate, particularly
with the
projected growth in air traffic. Because, it may be that the future envisaged
low-NOX combustor technologies may not keep up with the industry requirements for
increased engine thermal efficiency, the potential benefits from optimising aero engine
cycles and flight operations for low mission emissions deserve to be thoroughly
investigated.
The SKY computer simulation system developed to examine such alternative routes
integrates flight route performance, aero engine performance and the formation of
pollutants within the combustor. Based on Turbomatch, Cranfield Gas Turbine
Simulation System, SKY can be used to optimise mission/aircraft/engine/combustor
combinations with respect to landing and take-off (LTO) as well as mission emissions.
A model of the high capacity Boeing 747-400 powered by Turbomatch high bypass
ratio turbofan models and simulated on long range routes such as London-Tokyo is
selected for this work.
On the one hand, aero engine cycles can be designed at a optimum bypass ratio and
deliver mission NOX reductions of up to 10% over designs optimised for LTO NOX,
indicating that the current ICAO regulatory regime is a inadequate parameter to control
mission NOX. On the other hand, operational measures such as speed reductions could
bring further reductions of the order of 10%, but some of the improvement would be
made at the expense of fuel burn, CO2 and H20 emissions, payload-range capability and
direct operating costs.
The benefits from such alternative routes are not negligible but smaller in comparison to
the 30 to 80%
potential cuts from future low-NOX technology, as well as to the 30%
reduction due to expected improvements in the next 20 years or so in airframe weight
and aerodynamics and more efficient navigation practices.
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