Only a few data are available up to now on the potential impact of nitrous oxide emissions from commercial aero engines on the global N2O budget, particularly with respect to different flight, i.e. engine operating, conditions. Wiesen et al published in 1994 and 1996 emission data from two modern commercial aero engines, namely a Rolls Royce RB211 engine, which is still being used, for example in Boeing B747 aeroplanes, and a Pratt & Whitney Canada PW305 engine, which is used in smaller business jets. Both engines were tested in an altitude test facility, which was used to simulate real-flight conditions. The authors used gas sampling - taking into account sampling line artefacts - and off-line analyses of the gas samples by tunable-diode laser spectrometry. Within the experimental errors the N2O emission data obtained from the altitude test of the PW305 engine showed neither a dependence on the altitude nor on the engine speed. For the RB211 engine, the N2O concentrations were found to increase slightly with increasing engine power, with a much higher N2O emission index than for the PW305. The authors proposed an average N2O emission index of 0.15 g N2O kg-1 fuel. Taking into account the global annual fuel consumption for air transportation, one can conclude that the present contribution of this transport sector to the global N2O emission is small if not negligible.
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