Aviation and the Global Atmosphere

Aviation and the Global Atmosphere
much lower level. Both are products of incomplete combustion; thus, they are controlled by the same mechanism.
Despite the intrinsic complexity of the chemical processes associated with soot production, a semi-empirical correlation between calculated and measured SN has
been developed with a 40% standard deviation (De Champlain et al., 1997). By also considering reaction kinetics, Döpelheuer (1997) developed a correlation method
based mainly on the concentration of carbon and oxygen in the combustion zone. The concentration of soot is considered to be proportional to the equivalence ratio, to
pressure at the combustor inlet (both with exponents to be determined), and to an exponential function controlling the reaction rate. To apply the method as a
reference type of correlation, soot density as a function of measured SN (Finch and Eyl, 1976; Whyte, 1982; Champagne, 1988; Hurley, 1993) has been approximated
as a first step. Up to a 20% deviation exists between different correlations of soot loading and SN.
Because of the limitations of the standard measuring method for SN (i.e., by collecting soot on a white filter paper and evaluating reflected light intensity) (ICAO, 1993),
only the major particles of soot are measured; the remaining wide spectrum of very small particles are not measured (see Section 7.5.3).
7.7.2.2. Simplified Alternate Correlation Methods
The methods described above to correlate engine emissions for different operating conditions all require engine internal gas path data. Such data are normally
sensitive from an engine manufacturer's point of view. Alternate correlation methods that do not expose proprietary or sensitive engine data have therefore been
sought. These methods are based mainly on emission correlation with the fuel flow of an engine. Thus, SLS engine test data from certification testing, together with
relevant methods of correlating emissions with engine performance in flight, is favored as one of the principal sources for the development of aircraft emission
inventories. These methods are designed to use unrestricted data from the ICAO engine emission databank coupled with fuel flow data, which can easily be acquired
from aircraft missions.
Table 7-9: Comparison of relevant properties of ICAO fuel for emissions testing and commercial jet fuels.
Property ICAO
ASTM D 1655
Jet A/Jet A-1
Allowable Range of Values
DEF STAN 91-91
Jet A-1
Density (kg m -3 ) at 15°C 780-820 775-840 775-840 99.9
10% boiling point
Final boiling point
155-201
235-285
a 205
b 300
a 205
b 300
Net heat of combustion (MJ kg -1 ) 42.86-43.50 b 42.8 b 42.8 100
Aromatics (vol %) 15-23 a 25 a 22a 99
Naphthalenes (vol %) 1.0-3.5 (< 3.0)b (< 3.0)b 98.5
Smoke point (mm) 20-28 b 25b b 25b 99.3
http://www.ipcc.ch/ipccreports/sres/aviation/108.htm (2 von 5)08.05.2008 02:43:44
% UK Fuels
Meeting ICAO (1997)
100
99