A Fuel Switch for Future Farms
by John Blum (Marquette University) A new combustion system for engines allows heavy-duty farm equipment normally powered by diesel fuel to run on gasoline and ethanol, without sacrificing performance. — Having grown up working on his uncle’s farm and in his father’s concrete business in northern Illinois, Dr. Adam Dempsey knows a few things about agricultural and construction equipment — and, as an assistant professor of mechanical engineering, a lot of things about the diesel engines that run them. He was recently awarded a $2.5 million Department of Energy grant to develop a new supportive combustion system that will allow diesel engines in farm equipment to run on ethanol and ethanol-gasoline mixtures. The result will be an engine that packs the punch of diesel while delivering cleaner fuel emissions.
Although diesel engines have been long admired for their reliability and performance capabilities — pulling heavy loads at low speeds and burning fuel efficiently — they are also notorious for spewing soot and greenhouse gases, such as nitrogen oxides (NOx) and carbon dioxide (CO2). Farm equipment is part of a larger category of off-road vehicles that emit around 175 million tons of CO2 annually.
“While personal transportation and its effects on air quality and climate change are always in the public eye,” Dempsey notes, “the off-road sector is also a really big contributor to climate change.”
Dempsey’s research is working out how to power heavy-duty machinery using cleaner fuels such as gasoline and ethanol, which don’t typically generate the force necessary for the most demanding tasks.
To do that, he needs to address how the engine combusts the fuel. Typical automobile engines mix gasoline (and ethanol) with air inside a piston chamber, where it’s compressed and ignited by a spark plug. Diesel engines don’t have spark plugs. The fuel is ignited by the heat of extremely compressed air. The challenge with burning gasoline and ethanol in a conventional diesel engine is that these fuels are very difficult to ignite with just hot compressed air. They are very resistant to autoignition.
To achieve this “best-of-both-worlds” approach — diesel performance with cleaner fuel emissions — Dempsey has designed a new ancillary combustion system for a diesel engine.
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The new system is “fuel agnostic,” meaning it will work with any biofuel or biofuel mix with gasoline. For this project, he’s focusing on E15, a mix of 15% ethanol and 85% gasoline, given its ready availability, and E100, pure ethanol.
By project’s end, Dempsey hopes to have in hand a heavy-duty flex-fuel engine capable of reducing life-cycle CO2 emissions by about 15% compared with diesel fuel when operated on E15 and by about 50% when operated on pure ethanol.
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Coming on board the project early was Deere & Co., makers of agricultural equipment.
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He has assembled a team of business partners and the University of Wisconsin–Madison’s Engine Research Center that proposes to apply his prechamber ignition concept to natural gas engines. READ MORE
