Gasoline-diesel cocktail: a potent recipe for cleaner, more efficient engines
http://www.news.wisc.edu/16945
Aug. 3, 2009

by Brian Mattmiller

Diesel and gasoline fuel sources both bring unique assets and liabilities to powering internal combustion engines.

But what if an engine could be programmed to harvest the best properties of both fuel sources at once, on the fly, by blending the fuels within the combustion chamber itself?

The answer, based on tests by the University of Wisconsin-Madison engine research group headed by Rolf Reitz, would be a diesel engine that produces significantly lower pollutant emissions than conventional engines, with an average of 20 percent greater fuel efficiency as well.

These 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.

Under heavy-load operating conditions for a diesel truck, the fuel mix in Reitz's 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's strategy, just the right amount of diesel fuel injections provide the kick-start for ignition.

"You can think of the diesel spray as a collection of liquid spark plugs, essentially, that ignite the gasoline," says Reitz, the Wisconsin Distinguished Professor of Mechanical Engineering. "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."

Reitz will present his findings today (Monday, Aug. 3) at the 15th U.S. Department of Energy (DOE) Diesel Engine-Efficiency and Emissions Research Conference in Detroit.

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. 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 (commonly used in gasoline engines), instead of the high-pressure injection required by conventional diesel engines.

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 Engine Research Center. The results were "really exciting," 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.

"For a small engine to even approach these massive engine efficiencies is remarkable," Reitz says. "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."

Thermal efficiency is defined by the percentage of fuel that is actually devoted to powering the engine, rather than being lost in heat transfer, exhaust or other variables.

"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," Reitz says.

That is a major commercial concern as the bar set by the 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.

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 pressure fuel injection is needed to reduce soot formation in the combustion chamber.

Both of those processes are expensive and logistically complicated, Reitz says. Both primarily address cleaning up emissions, not fuel efficiency. The new 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 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 for both diesel and gasoline fuel, but so would urea, which is carried in a separate tank.

The big-picture implications for reduced oil consumption are even more compelling, Reitz says. The United States consumes about 21 million barrels of oil per day, about 65 percent (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 current levels, the nation could reduce oil consumption by 4 million barrels per day, or one-third of all oil destined for transportation.

"That's roughly the amount that we import from the Persian Gulf," says Reitz.

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.

The work is funded by DOE and the College of Engineering Diesel Emissions Reduction Consortium, which includes 24 industry partners.


Gasoline used as Diesel 'spark plug' improves economy and emissions
http://www.gizmag.com/diesel-s...plug-gasoline/12484/
By Michael Mulcahy

23:18 August 11, 2009 PDT

The most fuel-efficient diesel engine in the world, the Wärtsilä RTA96C, converts 50% of fuel into power. Researchers have now achieved better efficiency with a gasoline-diesel mix

The two engine technologies tend to be regarded as completely separate, so we rarely contemplate how gasoline and diesel can work together. But, in a series of tests conducted at the University of Wisconsin, scientists have used an engine’s fuel injection to produce the optimal diesel-gas mix for any given moment. The results are impressive: an average 20% greater fuel efficiency; combustion temperatures reduced by up to 40%; and effortless meeting of the stringent EPA 2010 emission regulations. Plus, the researchers believe that if their findings were implemented into every gasoline and diesel engine in the US, the savings could be as great as 4 million barrels of oil daily.

Because it’s less reactive and won’t burn so easily, gasoline could normally never fuel a diesel engine. However, the fuel-injected diesel becomes a kind of liquid spark plug, providing a kick-start for ignition. The fuel mix varies depending on circumstance: a heavily-laden truck might require a mix as high as 85% gasoline to 15% diesel, while a light load would require a roughly 50-50 blend. 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, determines the correct mix.

While the theory was initially computer-modeled, researchers put it to the test using a heavy-duty Caterpillar diesel engine. The test confirmed two of the greatest benefits of blended fuel combustion.

First, the combustion temperatures were reduced by as much as 40%, meaning far less energy was lost from the engine through heat transfer. Second, the customized fuel mix optimized combustion, with less unburned fuel lost in the exhaust and fewer emissions. (In fact, the process easily achieves the EPA’s requirement that 90% of soot and 80% of nitrogen oxide be eliminated from diesel emissions by 2010.)

In combination, these helped the test engine achieve a best result of 53% thermal efficiency. Thermal efficiency, basically, measures the percentage of fuel converted into power, and not lost in heat transfer or exhaust. The figure of 53% mightn’t seem like a lot, but so far the most fuel-efficient diesel engine in the world can only achieve a best figure of 50%.

The very good news is that this idea is, relatively speaking, fairly easy to implement. The scientists believe it will work just as well with the low-pressure fuel injection of gasoline engines as with diesel’s high-pressure valves. And, because gasoline engines average only 25% thermal efficiency, the potential for fuel economy is even greater.

The research group estimates that, if every gasoline and diesel engine in the U.S. converted to this blended fuel process – and achieved an overall thermal efficiency of 53% - oil consumption would reduce by about 4 million barrels a day, a little under a third of today's current consumption. Little wonder the Department of Energy has its funding fingers in this pie.

Good find, I don't think I am going to try there 50/50 blend but the 10% gasoline in my cold veg blend seems to work fine. Other folks running cold blends in Ford diesels indicate they regularly run 20% gasoline.

The Univ of wisconsin at Madison seems to be out ahead of most in coming up with practical application improvments for current tech but they don't seem to give many details, they put out a lot of press releases but when I have tried to dig deeper on the university's web pages I have not found any of the research papers to be available on line. I HAVE found more info after some period of time, usually in the form of another press release indicating that the grad student researcher and the research professor had formed a corperation and liscenced the development to one or the other big oil companies.

I also add up to 10% gasoline to my winter blend fuel because it helps ensure clean cold starts. I find it's unnecessary in summer blends.

The gasoline/diesel blends mentioned in the article will probably work OK in an engine specifically designed for that. However since gasoline is more expensive than diesel fuel I don't see much advantage with more than a small percent.

Many college and university research departments get the majority of their funding from corporations not tax dollars. Corporate funding usually comes with 'strings attached', which specifically limit publication of results, especially when the research has commercial applications. The general public does not want to see their tax dollars spent on university research they can't understand; corporate funding is often the only way to keep a research department alive.

quote:

Originally posted by john galt:
I also add up to 10% gasoline to my winter blend fuel because it helps ensure clean cold starts. I find it's unnecessary in summer blends.

Through almost 3 years of RUG blending experience I have come to hold the view for some time now that a percentage of unleaded in my oil gives better starts, cleaner running and better power although many have argued with this and basically said it isn't possible. This information would seem to support the position that RUG blending is very beneficial and it's nice to see some confirmation for an idea one had suspected all along.

I guess the fact that there are a number of us here all getting good results also adds weight to what we have found and supports the practice.

quote:

However since gasoline is more expensive than diesel fuel I don't see much advantage with more than a small percent.

Yes John, but as I know you would agree, cost isn't everything.
When you think about it, this is just a technological way of achieving what you have already accomplished through your clean testing Blends!

For those without the knowledge, patience or inclination to do what you do to get lower emissions, this would give the unwashed, ignorant and lazy, a much better outcome from their tail pipe!.

It would seem to me that a system like this would be relatively easy to tweak to run Bio and SVO in and achieve good cold starts and elimination of issues such as coking. Perhaps instead in seeing a steady decline in Veg/Bio capable vehicles, the tide may turn and new models will be the most suited of all engines to run Bio based fuels in?

Of course, the US Government has been running blends in their military vehicles for decades...

As I understand it, they weren't supposed to run on 100% gasoline, but could run fine with gasoline/diesel blends, or also blending in motor oil and other more viscous oils.

I think the goal was the ability to adapt to local resources rather than efficiency.

Well, yes, sorta. The older generation of 2 1/2 and 5 ton 6 X 6 vehicles had what was known as a "multi-fuel" diesel engine, this was supposed to run on about anything that you ran through it, and for the most part, it did. Unfortunatly one of the ways they did this was that the fuel injectors were designed to squirt A SOLID STREAM of liquid directly into a very deep pocket in the pistons that had a wierd swirl designed in, this worked but if you ever saw one of these engines run they belched huge amounts of smoke even on good diesel, they added turbos eventually and that helped a bit. BUT, according to what I have read, and from the military surplus dealer that I used to wholesale stuff to, they did not last vary long on straight gasoline.

Duelfuel did make a few posts from the gulf that he was running one on pure used lube oil from the motorpool because they would not issue him any diesel for the shop truck he was living in so the "multi-fuels" seems to burn heavy oil ok if you can stand the smoke, oh yah, he also said they blew a lot of liquid oil drops out the exhaust stack when started cold. I suspect they would have handled a blend with gasoline just fine though.

The article says they used a Caterpillar heavy-duty diesel engine for there tesing, It would be nice to find more info on this testing but I am doughtfull.

Speaking of dual fuel, my brother at Ford told me about the new "bobcat" engine. Uses direct injection like a diesel to vary percentages of gasoline and ethanol. Provides plenty of power as well as increased economy.

http://www.ridelust.com/fords-...h-a-gasoline-chaser/

I have used some gasoline in my blends as well as very small amounts of toluene. I've also used naptha in place of gasoline in my blend. However my van seems to like kero/wvo blends best.

I'm one of those guys who would love to have a multifuel 6x6 military vehicle as a daily driver LOL!

When most car engines can run E85 straight, why build in a complicated dual tank system?

And, why design it to run E85 rather than E100?

I.E.
Like they do in Brazil, use a little gasoline to get the thing rolling, then switch over to 100% E85 or E100.

Dual injectors would certainly help eliminate the mixing of fuels and the requirement to switch fuels and run a purge cycle prior to shutdown.

I would, however, worry about not using a direct cylinder injector 100% of the time might cause it to burn or clog. A redundant manifold injector, on the other hand, could be used as needed.

A while ago I saw some notes on running Ethanol in Diesel Cars...

Looking for it again, I found some notes on Saab, Fiat, and a conversion company named BSR.

http://www.e95.eu/
http://www.bsr.se/images/upload/BEST-2-2008-Juni.jpg
http://green.autoblog.com/2008...el-engine-in-brazil/

From my understanding the E85 is sprayed in as a power enhancer. The engine has very high compression for a gasoline engine, the E85 cools the cylinder under heavy acceleration to prevent detonation and thus allow more power to be realized from high compression without requiring high octane race gas. The trouble with alcohol only as a fuel is because more alcohol is required than gasoline, something like 3:1 if i recall correctly. This way the car cruises along on gasoline most of the time and under light loads detonation is not an issue, hammer the go pedal and the ethanol kicks in. Rumor has it this engine or one like it may even replace diesels in the 1 ton lineup.

Many folks are currently doing a similar thing by adding a water/alcohol fumigation setup to there diesel vehicles intake manifold, these usually only spray the water/alcohol into the intake manifold when the engine is under heavy load but a few run a duel setup, a small amount of spray all the time with a larger amount of spray under load. The amount of alcohol injected adds power and the water apparently cleans the cylinders and adds a bit of cooling to the intake air due to evaporation, this puts more air in the cylinder.

The 3-to-1 ratio for alcohol-to-gasoline is a bit high, more like 2 1/2-to-1 at the most, this is based on the amount of air that the engine can pump. Fueling with alcohol at 2 1/2 times the amount of gasoline will produce almost twice the power that you would get from gasoline in the same engine, you only need more alcohol if you want to make more power, for normal operation you would only burn a bit more alcohol than gasoline in an engine set up to mainly burn gasoline.

You can run a considerably higher compression ratio, spark advance, and a much leaner fuel/air mixture with alcohol without detonation (pinging), put all these fairly minor engine changes together and you can get even better milage than if burning gasoline. Even the low compressioned flat head 12 HP lawn tractor that I have been running on E85 for the last two summers makes considerably more power and gets better fuel economy with E85 than it ever did on gasoline, oil stays a LOT cleaner also.

Fueling a diesel using both gasoline and diesel apparently works (we know it does in a blend) but I would think that with a high percentage of gasoline as the fuel, and due to the diesel engine taking in max air at all throttle settings, you would have a rather lean gasoline/air mixture that would hammer the engine a lot at less than max engine load (could be wrong here, one of the arguments for Hydrogen fuel is that it burns faster thus making a much higher pressure in each cylinder earlier in the crank rotation period, this improves efficiency. The engine just needs to be strong enough to survive the added pressures). If the conventional diesel engine was at full load and ran a rich gasoline fuel mixture it might burn slow enough to be reliable? Now - A diesel engine fueled with alcohol, and modified to spark ignition, along with a carburetor or conventional indirect fuel injection (fuel into intake manifold rather than cylinder), should be a pretty efficient engine with plenty of power and should burn extremely clean.