Rolf Reitz, heading the engine research group at the University of Wisconsin-Madison is blending both diesel and gasoline fuel sources in the engine’s combustion chamber with models showing significantly lower pollutant emissions than conventional engines, with an average of 20 percent greater fuel efficiency as well. This is very big news.

Rolf D. Reitz of the University of Wisconsin

Rolf D. Reitz of the University of Wisconsin

The dramatic results came from a novel technique Reitz describes 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.

In Reitz’ strategy, just the right amount of diesel fuel injection provide the kick-start for ignition.  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.  In normal conditions this type of blend wouldn’t ignite in a diesel engine, because gasoline is less reactive than diesel and burns less easily.

Reitz explains, “You can think of the diesel spray as a collection of liquid spark plugs, essentially, that ignite the gasoline. The new strategy changes the fuel properties by blending the two fuels within the combustion chamber to precisely control the combustion process, based on when and how much diesel fuel is injected.”  At that point the speed of the harder to ignite gasoline pays off.

Two remarkable things happen in the gasoline-diesel mix, Reitz says. First, the engine operates at much lower combustion temperatures because of the improved control, as much as 40 percent lower than conventional engines, which leads to far less energy loss from the engine through heat transfer out to the engine components and the exhaust.

Second, the customized fuel preparation controls the chemistry for optimal combustion. That translates into less unburned fuel energy lost in the exhaust, and also fewer pollutant emissions being produced by the combustion process. In addition, the system can use relatively inexpensive low-pressure fuel injection as commonly used in gasoline engines, instead of the high-pressure injection required by conventional diesel engines.

The UW press release says, “Development of the blending strategy was guided by advanced computer simulation models. These computer predictions were then put to the test using a Caterpillar heavy-duty diesel engine at the UW-Madison Engine Research Center. The results were “really exciting,” says Reitz, confirming the predicted benefits of blended fuel combustion. The best results achieved 53 percent thermal efficiency in the experimental test engine. This efficiency exceeds even the most efficient diesel engine currently in the world — a massive turbocharged two-stroke used in the maritime shipping industry, which has 50 percent thermal efficiency.

Now that is a stunning level of efficiency, more than double what one expects from an automobile’s gasoline engine.

Reitz says, “For a small engine to even approach these massive engine efficiencies is remarkable.  Even more striking, the blending strategy could also be applied to automotive gasoline engines, which usually average a much lower 25 percent thermal efficiency. Here, the potential for fuel economy improvement would even be larger than in diesel truck engines.”  There’s an “Oh my,” moment for you.  Imagine the effect retrofitting  the world fleet would have on the economy.

Reitz also is watching the pollution control issue as diesels are just now getting deep into expensive control systems saying, “What’s more important than fuel efficiency, especially for the trucking industry, is that we are meeting the EPA’s 2010 emissions regulations quite easily.”  This matter is a major business concern as the bar set by the U.S. Environmental Protection Agency is quite high, with regulations designed to cut about 90 percent of all particulate matter (soot) and 80 percent of all nitrogen oxides (NOx) out of diesel emissions.

Its so serious a matter that some companies have pulled from the truck engine market altogether in the face of the stringent new standards. Many other companies are looking to alternatives such as selective catalytic reduction, in which the chemical urea (a second “fuel”) is injected into the exhaust stream to reduce NOx emissions. Others propose using large amounts of recirculated exhaust gas to lower the combustion temperature to reduce NOx. In this case, ultra-high high-pressure fuel injection is needed to reduce soot formation in the combustion chamber.  You can expect that these measures are not going to save much fuel and they are complex designs, expensive to build as well as run and maintain.

Reitz’s work of in-cylinder fuel blending strategy is less expensive and less complex, uses widely available fuels and addresses both emissions and fuel efficiency at the same time.

Reitz also says there is ample reason to believe the fuel-blending technology would work just as well in cars because dual-fuel combustion works with lower-pressure and less expensive fuel injectors than those used in diesel trucks. Applying this technology to vehicles would require separate tanks and fuel systems for both diesel and gasoline fuel.

Reitz also is obliged to explore the economy wide implications estimating that if all cars and trucks were to achieve the efficiency levels demonstrated in the project, it could lead to a reduction in transportation-based U.S. oil consumption by one-third.  He is using the common numbers where the United States consumes about 21 million barrels of oil per day, about 65 percent, about 13.5 million barrels of which is used in transportation. If this new blended fuel process could convert both diesel and gasoline engines to 53 percent thermal efficiency from today’s current levels, the nation could reduce oil consumption by 4 million barrels per day, or one-third of all oil destined for transportation.  That would be a major change in both the U.S. market and the world oil market of about 85 million barrels daily.

Here is the grain of salt – computer modeling and simulation provided the blueprint for optimizing fuel blending, a process that would have taken years through trial-and-error testing. Reitz used a modeling technique developed in his lab called genetic algorithms, which borrow some of the same techniques of natural selection in the biological world to determine the “fittest” variables for engine performance.

It seems to be the summer of speeding things up.

Reitz, the Wisconsin Distinguished Professor of Mechanical Engineering presented his findings Monday Aug. 3, 2009 at the 15th U.S. Department of Energy (DOE) Diesel Engine-Efficiency and Emissions Research Conference in Detroit. DOE and the UW-Madison College of Engineering Diesel Emissions Reduction Consortium, which includes 24 industry partners, fund the research. With that many interested industrial parties we might see something sooner than later coming to market.


3 Comments so far

  1. Matt on August 7, 2009 6:46 AM

    I can envision two fuel tanks for each heavy truck – one gas and one diesel. And, if the trucker ran out of gas he could run on diesel alone.

    Adoption in the passenger car market seems iffy. But – this could explode in the heavy truck segment.

  2. Scott T on August 7, 2009 8:46 AM

    There is an existing technology for running a diesel/natrual gas mix. It runs at a ratio of 20/80%. It has the same advantages as the diesel/gasoline mix.. It runs cleaner and the engine has a longer operational life.

    Where I see real application for mixed diesel fuel engines in the rail transportation industry, where fuel consumption is more predictable and more tightly managed.

  3. pradeepta on August 8, 2009 2:36 AM

    it’s a good idea sir…
    but don’t u think temperature is also a factor,which also greatly influences the eficiency of the vehicle..and the efficiency can also be increased if we also take the climatic conditions in which the vehicle is used,and program as such???

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