Fuels in Transportation - Decreasing Fuel Consumption and Exhaust Gas Emissions in Transportation - page 23

2.3 Aviation Fuels
There are two different types of fuels for airplane engines:
• Hydrogen carbon mixtures, mostly kerosene; and
• Mixing fuel, e.g., wide cut petroleum ether.
2.3.1 Kerosene
Kerosene has a leading position as a fuel in civil aviation [ 33 ]. It has a boiling
range of 160-250C (320-482F), is thoroughly cleaned and desulfurized, and
consists of 87% carbon and 13% hydrogen. About 5-8% kerosene is generally
produced in the distillation process of mineral oil by cracking. Cracking means the
splitting up of large hydrocarbon molecules into small ones. A concentration of
0.2-0.4% sulfur in the kerosene is allowed. Aromatic mercaptans provide the
typical kerosene smell.
The additive wide cut petroleum ether is available as an alternative jet B fuel
for civil aviation. It has a distillation range of 90-250C (194-482F) and consists
of up to 65% gasoline such as butane gas, pentane, hexane, and up to 35% cracked
kerosene. This composition allows the production of larger quantities at lower
prices. The low ignition point of 20C (68F) gives it the classification of the fire
class Al. Jet fuel B is solely used in the military because its flash point is lower and
it has a lower cold point than Jet fuel A. Civil aviation does not use Jet fuel B for
safety reasons [ 34 ].
Fuels for gas turbine jet engines must fulfill a number of demands:
• Low evaporation losses at higher altitudes;
• High boiling point, because of the danger of becoming too viscous in a cold
atmosphere;
• Low viscosity also at low temperatures for optimal spraying;
• No more than 15-20% volatile substances to avoid temperatures in the com-
bustion chamber that are too high;
• High lubrication ability from not too low viscosity to protect fuel valves and
pumps; and
• Near zero concentration of poisonous and corrosive sulfur compounds [ 35 ].
2.3.2 Testing Fuel for Engines
International Civil Aviation Organization (ICAO), Annex 16 Appendix 4 contains
the specifications for fuel to be used for testing in aircraft turbine engines (see
Table 2.10 [ 36 ]).