Performance Improvement and Emission Optimization of Natural Gas Engines for Passenger Cars

Natural gas as an alternative fuel is getting more attractive due to the improving resource situation, a growing supply network and easy refinding. The execellent combustion quality with reduced engine out toxic emissions currently allowsrelatively low emissions even without aftertreatment devices and leads to large conversion programs in areas with high local pollution. This article describes how low emission standards can be reached in combination with modern engine control technology strategies and advanced catalyst layout. Natural gas operation reduced the torque of a naturally aspirated engine due to fuel properties. The paper shows that an optimization of a naturally aspirated engine layout can reduce the loss significantly. The turbo charging of spark ignition engines using natural gas specific advantages can effectively overcome the volumetric effectively losses. The development of a vehicle with 1.81 turbo charged engine described in the paper shows the high potential in power and turbo with 80kW/l and approx. 20bars BMEP. CO2-emissions could be reduced not only in the NEDC driving cycle but also at maximum power by approx. 40% compared to a naturally aspirated gasoline engine of the same power output.