New CNG Concepts for Passenger Cars: High Torque Engines with Superior Fuel Consumption 2003-01-2264
Since the CO2 emissions of passenger car traffic and their greenhouse potential are in the public interest, natural gas (CNG) is discussed as an attractive alternative fuel. The engine concepts that have been applied to date are mainly based upon common gasoline engine technology. In addition, in mono-fuel applications, it is made use of an increased compression ratio -thanks to the RON (Research Octane Number) potential of CNG-, which allows for thermodynamic benefits.
This paper presents advanced engine concepts that make further use of the potentials linked to CNG. Above all, the improved knock tolerance, which can be particularly utilized in turbocharged engine concepts. For bi-fuel (CNG/gasoline) power trains, the realization of variable compression ratio is of special interest. Moreover, lean burn technology is a perfect match for CNG engines. Fuel economy and emission level are evaluated basing on test bench and vehicle investigations.
The result is an engine concept that offer not only low exhaust emissions, but has the high torque characteristics commonly known by HSDI diesel engines and a fuel consumption benefit that gives an Greenhouse advantage of 25…30% compared to diesel and even more compared to gasoline. That kind of “Downsizing” creates a customers' value based on high torque and low fuel costs that may make this kind of fuel more popular.