Vehicle Drive Cycle Fuel Economy Prediction Using Single Cylinder Engine Data 2019-01-0628
The confluence of fuel economy improvement requirements and increased use of ethanol as a gasoline blend component has led to various studies into the efficiency and performance benefits of using high octane number, high ethanol content fuels in modern engines.
As part of a comprehensive study of the autoignition of fuels in both the CFR octane rating engine and a modern, direct injection, turbocharged spark ignited engines, a series of fuel blends were prepared with market-relevant ranges for octane numbers and ethanol blends levels.
The paper reports on the first part of this study where fuel flow measurements were done on a single cylinder research engine, based on a GM LHU engine. For a range of engine speeds and manifold air pressures, spark timing was adjusted to achieve either the maximum brake torque (MBT) or a matched 50% mass fraction burned location. At operating conditions where combustion was knock limited, the spark was retarded to achieve a consistent knock intensity based on peak-to-peak pressure values as determined by in-cylinder pressure measurements.
These fuel flow measurements were used in a vehicle model to predict drive cycle fuel economy of a passenger car utilizing the same engine configuration and certification fuel. The precited fuel economy results over FTP-75, Highway and US06 drive cycles were compared with certification values and yielded a reasonable correlation without the need for model parameter adjustments. The model was then used to predict drive cycle fuel economy of the various fuel blends. Results revealed the impact of knock limit differences, as well as the impact of fuel energy density non-knock limited operating points