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Study: Adding Aluminum Nanoparticles to Diesel Can Improve Ignition Properties

Asunano
The addition of Al or Al2O3 nanoparticles increases the probability of ignition. Click to enlarge.

Adding aluminum and aluminum oxide nanoparticles to diesel can improve the fuel’s ignition properties, according to a new study published online in the journal Nano Letters.

Arizona State University mechanical engineer Patrick E. Phelan and colleagues varied both particle size (15 and 50 nm) as well as the volume fraction (0%, 0.1%, and 0.5%) of aluminum (Al) and aluminum oxide (Al2O3) nanoparticles at several temperatures within the range 688 °C up to 768 °C. In a series of hot plate studies, they found that in all cases the ignition probability of the nanoparticles + diesel mixtures was much higher than that of pure diesel.

Although several studies have shown that the addition of nanoparticles to solid fuels and propellants can result in shortened ignition delay, increased energy density, and high burn rates, there has been little work has been reported in the past on the effect of adding nanoparticles to liquid fuels, according to the researchers.

...ignition delay and ignition temperature are critical parameters that characterize the performance of a diesel engine. Both efficiency as well as emission levels from a diesel engine can potentially be improved by optimizing the ignition delay and ignition temperature....It was observed that the hot plate ignition probability of the diesel fuel increases significantly by the addition of the nanoparticles. Moreover, the presence of some residue particles on the hot plate surface is also believed to contribute to an increase in the ignition probability of pure diesel.

They found that neither the change in nanoparticle material nor the nanoparticle size influenced the ignition probability of the nanoparticle + diesel mixtures. The researchers suggest that adding nanoparticles to the fuel caused significant improvements in its radiative and heat/mass transfer properties and hence the droplets ignited at a much lower temperature and also more often as compared to pure diesel.

Such an increase in heat and mass transfer properties of the fuel has the potential of reducing the evaporation (and ignition) time of droplets within a diesel engine and hence should favorably influence its ignition delay. Moreover, SEM analyses of the hot plate surface indicate that the presence of residue particles on the hot plate surface may have also participated in the enhancement of the ignition probability of pure diesel.

Resources

  • Himanshu Tyagi, Patrick E. Phelan, Ravi Prasher, Robert Peck, Taewoo Lee, Jose R. Pacheco, and Paul Arentzen (2008) Increased Hot-Plate Ignition Probability for Nanoparticle-Laden Diesel Fuel, Nano Lett, DOI: 10.1021/nl080277d

Comments

tonychill

Didn't we just take the lead out of fuel?
ASU needs to spend just as much time determining health effects of these new particles in the air.

T. Ryan

I am all for technologies that will increase the efficiency of transportation but I would be concerned about the possible health risk to adding aluminum nanoparticles to our fuels.

Studies show that smaller particles are more damaging to the lungs and repertory track and I am curious what danger, if any, these particles might pose if inhaled in low dosages.

I assume that the average particle size is too small to be effectively filtered out without excessive back-pressuring of the motor using technologies. Are there any suggested methods for removing these particles prior to exhaust?
-TR

KZ

Seems to be similar effect to Oxonica's nano Cerium Oxide additives. See www.oxonica.com. Those are approved for use in the EU.

Mark

I hoped we learned our mistakes in the past of putting lead in gasoline. This method should never see the light of day. The sad thing is that this may reach the market behind the public's knowledge because of powerful lobbyist in washington that serves' their own interest and profit at the expense of the publics' health.

mjo

Aluminum has magnetic properties. Since the combustion temperatures would be less than the melting point of AL, I wonder if an AC magnet could be used to separate out the aluminum.

Eric Bischoff

I am not sure I like the idea of adding nano metal particles either. It's untested and could be disastrous for the lungs of children. We already are in an asthma epidemic. But there are already proven, non-toxic additives made up of carbon, hydrogen and oxygen esters that improve performance and mileage and reduce emissions.

John

NO! Don't do this. I foresee horrible problems. I would rather sniff rotten banana peels than be forced to breathe aluminum.

eric

first of all, neither aluminum nor aluminum oxide is magnetic. secondly, DPF's fitted as standard to modern diesel engines can already filter particles down to 50nm in size, so John you would not be forced to breathe it even if it were adopted. the fact that the effect was not affected by the change in particle size or material suggests that perhaps other, more benign materials would also have the same beneficial effect.

really, I am suprised at the Chicken-Little, Luddite-type response to this research (and that is all it is at present, a research paper).

Lulu

Does anyone like to have Aluminum plaque deposit in the brain?

Paul F. Dietz

Lulu: the link between aluminum and Alzheimer's Disease was debunked years ago. The original result turned out to be a laboratory artefact.

Rocket engineers have contemplated for years the addition of aluminum particles to liquid rocket propellants (kerosene, hydrogen, hydrazine). The stuff can cause modest increases in specific impulse and propellant density, both desirable effects.

really, I am suprised at the Chicken-Little, Luddite-type response

I've noticed a deplorable trend to poorly reasoned, shallow, nihilistic cynicism in these blogs. So you shouldn't be surprised.

brian

Well, I can't really find a lot of detail about the flash point of aluminum itself, but one industrial source indicates it is >536 degrees F. Some paper from the 70s indicates more like 980 C!!! but this was for a large (4mm) disc. Did anyone else see corn starch fireball demonstration in high school? Since the particles are so small, if you blow corn starch (just a handful) out of a rolled up letter size paper over a bunsen burner, a giant fireball is made of the cloud of corn starch, even though there's almost nothing you can do to ignite the corn starch if its still in a pile. So, the two questions are, I think, what happens in the case of a blending/manufacturing error (particles that are too large) and what is it that we're left with when nanoparticles vs large particulates of the aluminum.

Mark

Paul,

A lot of studies tried to reject correlation between toxic substance and direct effect to health. However, recent information also questioned the method of the process, the hidden motive of the study, the source of financing of the study, the correlation for long term effect and not just the short outcome, etc...

I am a medical doctor and I don't trust many of the new studies about drug developments mainly because most are funded by pharmaceutical companies that all they care is profit and even try to hide or downplay serious side effects.

Lulu

I found a 2006 publication "The Role Of Metals In Alzheimer's Disease Explored", Journal of Alzheimer's Disease. Anyway, the contributions of the metals could not be ruled out yet.

donee


Hi All,

I doubt this will go very far. Alumina (aluminum oxide) is the second hardest material known to man. So, the abrasion on the exhaust valves and exhaust components will be so bad, it will not be econonmic.

Oh, Aluminum and Alumina are both very non-magnetic. Other than filtering, the way to remove them from an exhaust fluid flow would be centrifucally. So, one would need something like a Dyson vacuum cleaner on the tail pipe.

And as another posters comment suggest, why not just burn corn nano-particles?

reed

shortening the ignition delay of diesel is a horrible idea, future HCCI engines want low cetane and high octane.
Also there are cheaper/easier ways to raise cetane too.

mjo

You're right, Aluminum is not a magnet. However, it can act like a diamagnet in the presence of alternating magnetic fields.

Ever see an aluminum ball or disk levitated by an AC-powered electric magnet?

Jay Tee

why not have nano-particles that contain hydrogen atoms? That will improve combustion.... There! I'm smarter than all the rest of you.

Rafael Seidl

Modern engines use extremely high fuel injection pressures (~2000 atmospheres) and extremely fine injection holes to achieve as much air-fuel mixture preparation as possible before compression ignition kicks in. This is results in smaller zones of rich mixture and therefore, reduced production of soot during the combustion phase. It also results in more rapid combustion and hence, higher RPM limits and rated power for passenger car diesel engines.

Ultrafine particles in the fuel are, however, a separate source of headaches. Over a number of years, they can cause erosion of the injector holes and the bearing surfaces of the high pressure fuel pump. These are among the most expensive components in the entire engine. Biodiesel (fatty acid methyl esters) naturally contains higher amounts of particulate matter and delivers lower lubricity than dinodiesel, one reason many manufacturers limit their warranty cover to B5 (except for Citroen PSA: B20).

Adding aluminum specs to diesel fuel might well improve ignition properties, but only at the expense of increased wear and tear on the fuel system. In addition, the flow-through DPFs now common on new European passenger cars would gradually seize up because metal oxides cannot be thermally purged. Using fuel or engine oil containing a metal-based additive is not recommended, as the DPF would have to be removed and mechanically cleaned or else replaced well before the vehicle reaches 10 years or 150,000 miles.

HDVs deal with engine-out PM using continuously regenerating traps (CRTs) which do not seize up. This is possible because the duty cycle of these vehicles operates the engine at high load much more frequently, increasing exhaust gas temperatures.

donee


Hi mjo,

That action requires eddy currents. The counter EMF is dependant on the area of the flowing eddy current. Nano-particles by definition, have low planar areas to support the eddy currents. This is why transformers are laminated, and powdered iron cores are used in switching power supplies. The thinner the plates, or smaller the powder particles, the less the eddy currents. The smaller the particle, the less the eddy current force.

mki

"change in nanoparticle material nor the nanoparticle size influenced the ignition"

Well why not add water?
It is proven many time that adding water impove the efficiency of ICE.
Water injection was extensiwly used in air plane engines during WWII.

Henry Gibson

With some work, they are used in buses, a Capstone turbine could be fitted to a hybrid car. Fuel burning is constant, and this would eliminate the particles. A recent version puts out cleaner air, except CO2, than it takes in. Remove most of the batteries from a TESLA and add a turbine pod and you might get better well-to-wheel effciency. Turbines have been run on methanol, ethanol, diesel, biodiesel natural gas and other fuels, and always produce low emmissions...HG....

mki

the Capstone turbine was discus in one of the previous post. It is not as efficient as it look.
At list 30% less efficient then any othere solution.

rob

If the actual particle doesn't matter, then this already happens any time the engine has the EGR solenoid open. Nano-sized bits of carbon soot in the intake charge...

Kent

Jay Tee is right on track. These results, observed on a hot plate in a laboratory, will almost certainly not translate well to existing automotive fuel systems. As for the environmental ramifications. DPF technology could probably be adapted to filter out the particles, but there are and probably always will be a whole lot of fuel burnt without the benefit of a DPF. Think generators, air compressors, construction equipment, all pre-DPF trucks and autos, not to mention diesel fuel that gets burned as heating oil. I personally dread the thought of particulate size metals and metal oxides floating around.

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