Effects of Lower Carbon Intensity Fuels on Performance and Greenhouse Gas Emissions Intensity Reduction for Conventional and Next Generation Powertrains Part I: Engine Test Results and WtW CO2 Emissions Estimation

The use of internal combustion engine vehicles (ICEVs) and hybrid electric vehicles (HEVs) powered by biofuels produced by photosynthetic fixation of CO₂ and synthetic fuels produced by industrial synthetic reactions can be an effective way to reduce well-to-wheel (WtW) greenhouse gas (GHG) emissions intensity from vehicles, including both new and legacy fleet. In this study, several lower-carbon intensity fuels that contain at least 50% of renewable components, have at least 40% lower carbon intensity compared to commercially available E10 gasoline, and meet applicable US fuel standards were evaluated in a naturally aspirated (NA) engine in the legacy fleet, a turbocharged engine in the legacy fleet, and a prototype turbocharged super lean-burn engine, to identify their effects on thermal efficiency and exhaust emissions. As a result, it was confirmed that the lower-carbon intensity fuel can provide almost equivalent engine power and thermal efficiency as conventional fuel, and good results were obtained for exhaust emissions, with equivalent or lower emissions of total hydrocarbons (THC) and a lower particle number (PN). No unique issues were observed with the lower-carbon intensity fuels during the engine tests in this study. In addition to the engine tests, WtW CO₂ emissions were calculated by using a calculation model capable of calculating CO₂ emission during vehicle driving. The results of the calculations showed that a turbocharged super lean-burn engine combined with a lower-carbon intensity fuel consisting of 100% renewable components could reduce the WtW CO₂ value by up to 58.5% in the US Federal Test Procedure (FTP) driving cycle compared to a combination of commercially available fuel and a NA engine under conditions assuming a current HEV system.