Topic 13d: Combustion Geometry Optimization to Increase Alcohol-Fueled MCCI Efficiency

Diesel engines are critical to modern economies—moving 70% of the nation’s goods—but they remain coupled to the need for petroleum-based Diesel fuel, which presents challenges. Diesel fuel prices are volatile (creating uncertainty about the fuel’s long-term economics), while the need for oil drives demand for imports. Emissions are challenging as well, as heavy-duty Diesel engines generate 5 Gt of CO2 globally, while also contributing 30% of the smog emissions in polluted regions like California’s South Coast air basin. Many of the alternatives to Diesel engines—such as spark ignited natural gas engines, or electric vehicles—lack the performance, range, or liquid-fueled simplicity that is required in many Diesel applications. To solve this problem, this project will “take the Diesel fuel out of the Diesel engine”, by modifying engines to use low-carbon liquid alternative fuels (like ethanol and methanol, which are not soot-producing) in a high-efficiency, Diesel-style combustion mode (but without the need for any Diesel fuel). This technology elevates combustion temperatures in order to enable use of these non-traditional fuels without sacrificing performance (in fact increasing power by 30%). It harnesses the economic and environmental benefits of the fuels—reducing fuel costs by 10%, CO2 emissions by 40%, and smog emissions by 90%—without requiring a significant change in user behavior. This Phase I effort will use both modeling and experiments to optimize combustion chamber geometry to harness the advantages of these clean-burning fuels, allowing this concept to achieve efficiencies that are comparable to the baseline Diesel engine. During Phase I, a validated Computational Fluid Dynamics model will be used to determine which piston geometries and spray characteristics are ideal for increasing the thermal efficiency of alcohol-fueled combustion. Since this strategy leverages the effectiveness of the three-way catalyst, it eliminates the need to design combustion geometry to minimize in-cylinder pollutant formation (as required in Diesel engines, which lowers efficiency). The most promising designs will be fabricated and tested in an engine test platform, and will demonstrate a 5% improvement in energy efficiency from the un-optimized baseline, and approach the peak efficiency achieved via traditional Diesel, but with much lower criteria pollutants, carbon impact, and fuel costs. This technology can be deployed in any sector that utilizes heavy-duty Diesel engines. The following Phase II effort will continue development by integrating the most efficient geometries into a commercial engine platform, allowing the concept to reach state-of-the-art Diesel engine efficiencies, and preparing for pilot testing in heavy-duty transportation engines in a Phase III project. Once deployed throughout the HD transportation sector, this technology would reduce global anthropogenic CO2 emissions by 2 Gt/year, while savings from lower fuel costs will be passed on to consumers in the form of lower cost of goods. Once finding success in transportation use of this technology can be expanded to other Diesel-dominated sectors, like agriculture, mining, construction, and marine.