Gasoline-deisel recipe for clean, efficient engines
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From left: Reed Hanson, Wisconsin Distinguished Professor of
Mechanical Engineering Rolf Reitz,
Derek Splitter and Sage Kokjohn.
(View larger
image)
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 rogramming vehicle engines to blend gasoline and diesel fuel in the combustion chamber could reduce the amount of transportation-based oil consumed in the United States by a third—roughly the amount imported from the Persian Gulf each year.
Wisconsin Distinguished Professor Rolf Reitz describes this novel technique as “fast-response fuel blending,” in which an engine’s fuel injection is programmed to produce the optimal gasoline-diesel mix based on real-time operating conditions. Under heavy-load operating conditions for a diesel truck, the fuel mix in Reitz’ fueling strategy might be as high as 85 percent gasoline to 15 percent diesel; under lighter loads, the percentage of diesel would increase to a roughly 50-50 mix. Normally this type of blend wouldn’t ignite in a diesel engine, because gasoline is less reactive than diesel and burns less easily. But in Reitz’ strategy, just the right amount of diesel fuel injections provide the kick-start for ignition.
In the gasoline-diesel mix, the engine operates at much lower combustion temperatures because of the improved control, which leads to less engine energy loss. The customized fuel preparation also controls the chemistry for optimal combustion, meaning less unburned fuel energy is lost in exhaust and fewer pollutant emissions are produced. In addition, the system can use relatively inexpensive low-pressure fuel injection (commonly used in gasoline engines), instead of the high-pressure injection required by conventional diesel engines. In the experimental test, the best results achieved 53 percent thermal efficiency (the percentage of fuel devoted to powering the engine). “For a small engine to even approach these massive engine efficiencies is remarkable,” Reitz says.
The work is funded by the U.S. Department of Energy and the College of Engineering Diesel Emissions Reduction Consortium, which includes 24 industry partners. Read more about the project at www.engr.wisc.edu/news/headlines/2009/Aug03.html.
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