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homogeneous combustion. The basic principle of this new combustion
modeconsistsof thepreparationof amuchmorehomogeneous air-gasoline
mixture in the combustion chamber. By getting a more homogeneous
temperature distribution and avoiding local temperature peaks, it is
possible to reduce sharply the formation of pollutants, namely nitrogen
oxides and soot. Homogeneous combustion can be used also in the case of a
diesel engine making it possible to maximise the yield, while reducing the
emissions of pollutants such as particles and nitrogen oxides (NO x )[46].
European passenger car manufacturers initially committed themselves
to reduce the emissions of CO 2 per covered kilometre, from 190 g/km in
1997 to 160 g/km in 2003, 140 g/km in 2008, and with the objective of
120 g/km in 2012.
Figure 5.3 illustrates the evolution of passenger car CO 2 emissions
within the European Union (UE 15). For about ten years, these emissions
have decreased at the rate of 1.4% per year. To achieve the objective for
2012, it would be necessary to have a decrease in rate of 3.3%per year in
the years to come.
It is apparent that these objectives will not be reached and the level of
constraints has been reduced. They are especially difficult to reach in the
case of spark ignition engines, due to efficiencies which are on average
lower than in the case of diesel engines. The objective for 2012 is nowfixed
at 130 g/km, a further reduction of 10 g/km being expected as a result of
other means (reduction in the carbon content of engine fuels). The weight
of the vehicle is also taken into account.
Figure 5.3 Evolution of passenger car CO 2 emissions within the European Union
(
Energie & Climat: Reussir la
Source
: IFP). Reproduced with permission from
by Alexandre Rojey, ยด ditions Technip, Paris, 2008
transition energetique
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