Flex Fuel Gasoline-Alcohol Engine for Near Zero Emissions Plug-In Hybrid Long-Haul Trucks

Internal combustion engines for plug-in hybrid heavy duty trucks, especially long haul trucks, could play an important role in facilitating use of battery power. Power from a low carbon electricity source could thereby be employed without an unattractive vehicle cost increase or range limitation. The ideal engine should be powered by a widely available affordable liquid fuel, should minimize air pollutant emissions, and should provide lower greenhouse gas emissions. Diesel engines could fall short in meeting these objectives, especially because of high emissions. In this paper we analyze the potential for a flex fuel gasoline-alcohol engine approach for a series hybrid powertrain. In this approach the engine would provide comparable (or possibly greater) efficiency than a diesel engine while also providing 90 around lower NOx emissions than present cleanest diesel engine vehicles. Ethanol or methanol would be employed to increase knock resistance. Engines that could be deployed in the relatively near term could also use high rpm operation and /or water injection, to allow operation with a very small amount of alcohol in addition to a low concentration mixture such as E10 (or possibly with no additional alcohol). Further NOx reduction (by use of higher levels of EGR) and increased efficiency (by use of alcohol enhance heat recovery) could potentially be obtained over a longer term. While the analysis shows the potential for substantial benefits of using this approach, more detailed engine modeling is needed to provide more accurate illustrative engine features.