Potential of the Turbocharged Monovalent CNG Engine for Passenger Cars

Authors

Frank Otto, Klaus Rößler, Christoph Bertram, DaimlerChrysler AG, Stuttgart, Alois Fürhapter, AVL List GmbH, Graz

Year

2007

Summary

Presumably, compressed natural gas (CNG), but also biogas, will play an important role for passenger car fueling in the future. This is due to a better CO2 balance as well as a large amount of natural ressources. So far, bivalent powertrain concepts are dominant, whereby gasoline operation is defining the concept. With a further growth of the number of CNG power stations, however, monovalent engine concepts will increasingly attract interest. This is for reasons of improved fuel economy and, thereby, extended cruising range. In this report, the potential of such monovalent concepts is presented. The focus lies on turbocharging, increased compression ratio, lean operation and direct injection, accompanied by measures of improved mixture formation and charge motion. Part load as well as full load results are discussed. Testing devices are a turbocharged port-injected 4-cyl. engine and a direct-injected 1-cyl. engine. For realization of CNG direct injection, an injector with outwardly opening nozzle built by AVL was used. Finally, specific aspects of exhaust gas aftertreatment of CNG engines are discussed, with a special focus on the problems related to the high catalyst light-off temperature of methane.

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