Fuel Economy and Greenhouse Gas Reduction Potentials of Advanced Combustion Modes in Light-Duty Vehicles: A Well-to-Wheel Analysis using Vehicle Systems Simulations with Experimental Engine Data

Vehicle fuel efficiency and emissions regulations are driving a radical shift in the need for high efficiency powertrains along with control of criteria air pollutants and greenhouse gases. High efficiency powertrains including vehicle electrification, engine downsizing, and advanced combustion concepts all seek to accomplish these goals. Homogeneous charge compression ignition (HCCI) concepts have been proposed have not been able to demonstrate the controllability to operate over a sufficient engine speed and load range to make it practical for implementation in production vehicles. In-cylinder blending of gasoline and diesel to achieve reactivity controlled compression ignition (RCCI) has been shown to reduce NOX and PM emissions while maintaining or improving brake thermal efficiency as compared to conventional diesel combustion (CDC). The RCCI concept has an advantage over many advanced combustion strategies in that the fuel reactivity can be tailored to the engine speed and load allowing stable low-temperature combustion to be extended over more of the light-duty drive cycle load range. The potential for advanced combustion concepts such as RCCI to reduce drive cycle fuel economy and emissions is not clearly understood and is explored in this research by simulating the fuel economy and emissions for a multi-mode RCCI-enabled vehicle operating over a variety of U.S. drive cycles using experimental engine maps for multi-mode RCCI, CDC and a 2009 port-fuel injected (PFI) gasoline engine. Simulations are completed assuming a conventional mid-size passenger vehicle with an automatic transmission. RCCI fuel economy simulation results are compared to the same vehicle powered by a representative 2009 PFI gasoline engine over multiple drive cycles Engine-out drive cycle emissions are compared to CDC and observations regarding relative gasoline and diesel tank sizes needed for the various drive cycles are also summarized. The well-to-wheel energy and greenhouse gas emissions from these drive cycle simulations running carious amounts of biofuels are examined and compared to the state-of-the art in conventional, electric and hybrid powertrains.