Natural gas is a 'clean' and true alternative fuel whose validity and reliability have been proven in the last decade through its application on FIAT Group CNG vehicles, both in the passenger car and in the heavy duty sector. Environmental potential, resulting in regulated and unregulated emission reduction, as well as in containing GHG emission are key points. Moreover, the high knock resistance of methane allows an incremental benefit in terms of fuel economy coming from the compression ratio optimization / turbocharging. Taking into account the actual trends of the evolution of the SI engines towards higher torque/power densities with higher efficiencies, CNG (Compressed Natural Gas) appears as a very promising fuel to reach ambitious targets of C02 reduction, avoiding rich operating mode under full load conditions and providing a better air-fuel mixing without wall wetting phenomena during dynamic transients. However, a constraint in the power density increase could be represented by high thermal flow to the cylinder head, with a possible solution through the engine design review or by adopting specific combustion approach under full load conditions. A fundamental improvement is also expected by the use of the Multiair electrohydraulic system to manage the air flow at the intake cycle by cycle: by this means, throttling operations are avoided and, as consequence, the removal of pumping losses can provide an incremental reduction of C02 emission by 10 to 12%. Moreover, always from the point of view of the C02 avoidance, the incoming development of the 'renewable' pathway of biogas could strongly improve the global WTW assessment; natural gas can be, in fact, produced by anaerobic digestion or thermal gasification of a wide variety of biomass: with a successive step of refinement, biogas is then upgraded to natural gas and can be used directly as automotive fuel or added to fossil methane in the existing distribution network. Finally, novel use of natural gas/biogas blended with controlled amounts of hydrogen results in amplifying the environmental benefit of pure methane, all by using as base reference the CNG engine/vehicle technologies. In this way, with an evolutive approach, hydrogen could be gradually introduced into the automotive market, enhancing not only its production and distribution pathway, but also the creation of the necessary standards framework and knowledge diffusion for the public acceptance.
CNG for propulsion: changes and challenges
Erdgas für Antriebe: Entwicklungen und Herausforderungen
Alternative Antriebe für Automobile, 2006, Alternative Propulsion Systems for Automobiles, 2006 ; 258-274
2007
17 Seiten, 17 Bilder, 15 Quellen
Aufsatz (Konferenz)
Englisch
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