Laser sparks revolution in internal combustion engines

Apr 20, 2011

For more than 150 years, spark plugs have powered internal combustion engines. Automakers are now one step closer to being able to replace this long-standing technology with laser igniters, which will enable cleaner, more efficient, and more economical vehicles.

In the past, lasers strong enough to ignite an engine's air-fuel mixtures were too large to fit under an automobile's hood. At this year's Conference on Lasers and Electro Optics (CLEO: 2011), to be held in Baltimore May 1 - 6, researchers from Japan will describe the first multibeam system small enough to screw into an engine's cylinder head.

Equally significant, the new is made from ceramics, and could be produced inexpensively in large volumes, according to one of the presentation's authors, Takunori Taira of Japan's National Institutes of Natural Sciences.

According to Taira, conventional spark plugs pose a barrier to improving fuel economy and reducing emissions of (NOx), a key component of .

Spark plugs work by sending small, high-voltage electrical sparks across a gap between two metal electrodes. The spark ignites the air-fuel mixture in the engine's cylinder—producing a controlled explosion that forces the piston down to the bottom of the cylinder, generating the horsepower needed to move the vehicle.

Engines make NOx as a byproduct of combustion. If engines ran leaner – burnt more air and less fuel – they would produce significantly smaller NOx emissions.

Spark plugs can ignite leaner fuel mixtures, but only by increasing spark energy. Unfortunately, these high voltages erode spark plug electrodes so fast, the solution is not economical. By contrast, lasers, which ignite the air-fuel mixture with concentrated optical energy, have no electrodes and are not affected.

Lasers also improve efficiency. Conventional spark plugs sit on top of the cylinder and only ignite the air-fuel mixture close to them. The relatively cold metal of nearby electrodes and cylinder walls absorbs heat from the explosion, quenching the flame front just as it starts to expand.

Lasers, Taira explains, can focus their beams directly into the center of the mixture. Without quenching, the flame front expands more symmetrically and up to three times faster than those produced by spark plugs.

Equally important, he says, lasers inject their energy within nanoseconds, compared with milliseconds for spark plugs. "Timing – quick combustion – is very important. The more precise the timing, the more efficient the combustion and the better the ," he says.

Lasers promise less pollution and greater fuel efficiency, but making small, powerful lasers has, until now, proven hard. To ignite combustion, a laser must focus light to approximately 100 gigawatts per square centimeter with short pulses of more than 10 millijoules each.

"In the past, lasers that could meet those requirements were limited to basic research because they were big, inefficient, and unstable," Taira says. Nor could they be located away from the engine, because their powerful beams would destroy any optical fibers that delivered light to the cylinders.

Taira's research team overcame this problem by making composite lasers from powders. The team heats the powders to fuse them into optically transparent solids and embeds metal ions in them to tune their properties.

Ceramics are easier to tune optically than conventional crystals. They are also much stronger, more durable, and thermally conductive, so they can dissipate the heat from an engine without breaking down.

Taira's team built its laser from two yttrium-aluminum-gallium (YAG) segments, one doped with neodymium, the other with chromium. They bonded the two sections together to form a powerful laser only 9 millimeters in diameter and 11 millimeters long (a bit less than half an inch).

The composite generates two laser beams that can ignite fuel in two separate locations at the same time. This would produce a flame wall that grows faster and more uniformly than one lit by a single laser.

The laser is not strong enough to light the leanest fuel mixtures with a single pulse. By using several 800-picosecond-long pulses, however, they can inject enough energy to ignite the mixture completely.

A commercial automotive engine will require 60 Hz (or pulse trains per second), Taira says. He has already tested the new dual-beam laser at 100 Hz. The team is also at work on a three-beam laser that will enable even faster and more uniform combustion.

The laser-ignition system, although highly promising, is not yet being installed into actual automobiles made in a factory. Taira's team is, however, working with a large spark-plug company and with DENSO Corporation, a member of the Toyota Group.

Explore further: Germanium tin could mean better and cheaper infrared cameras in smartphones

More information: CLEO: 2011 presentation CMP1, "Composite All-Ceramics, Passively Q-switched Nd:YAG/Cr4+:YAG Monolithic Micro-Laser with Two-Beam Output for Multi-Point Ignition," by Nicolaie Pavel of Romania's National Institute for Laser, Plasma and Radiation Physics; Takunore Taira and Masaki Tsunekane of Japan's Institute for Molecular Science; and Kenji Kanehara of Nippon Soken, Inc., Japan, is at 1:30 p.m. Monday, May 2 in the Baltimore Convention Center.

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User comments : 34

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baudrunner
1.5 / 5 (17) Apr 20, 2011
I predict that this idea, although attractive, will be shelved for security reasons. Laser components this powerful can do serious damage and can be adapted to home-made weaponry.
sstritt
4.1 / 5 (17) Apr 20, 2011
I predict that this idea, although attractive, will be shelved for security reasons. Laser components this powerful can do serious damage and can be adapted to home-made weaponry.

High power density, yes, but only 10mJ energy per pulse. Not that scary.
NameIsNotNick
4.5 / 5 (16) Apr 20, 2011
Weapon, I don't think so... but it could be the break-through we've been anxiously waiting for to reliably ignite the BBQ.
CapitalismPrevails
1 / 5 (7) Apr 20, 2011
Would this make the bloom box irrelevant?
Yogaman
1 / 5 (2) Apr 20, 2011
Aren't YAG lasers typically 1% efficient? (That's what google says.)

If so, although the required ignition power is only a few watts ("several" * 10 mJ * 60 Hz) per cylinder, the engine would need a few toasters worth of new electrical supply.

Perhaps this is the real reason car makers are not enthusiastic.
d_robison
not rated yet Apr 20, 2011
Aren't YAG lasers typically 1% efficient? (That's what google says.)

If so, although the required ignition power is only a few watts ("several" * 10 mJ * 60 Hz) per cylinder, the engine would need a few toasters worth of new electrical supply.

Perhaps this is the real reason car makers are not enthusiastic.


Could be, I couldn't find anything on their efficiency but I did find a lot on who uses them. It seems fairly common in dentistry, medicine (oncology, hysteroscopy...), military/defense, etc. So I would assume that it is probably not terribly inefficient (especially since it's used in medicine, hospitals try to cut costs wherever they can). I could be wrong though.
gmurphy
5 / 5 (5) Apr 20, 2011
Long-term viability would have to be demonstrated too, engines are grimy, vibrating and hot, the lasers would have to tolerate these conditions for years without degrading in performance. That said, the benefits of cleaner burning fuel are more than enough reason to pursue this tech.
bfast
Apr 20, 2011
This comment has been removed by a moderator.
freethinking
1 / 5 (7) Apr 20, 2011
I had this idea years ago, should have written in up and patented it.... rats
bg1
4 / 5 (4) Apr 20, 2011
What about fouling of the lens through which the laser beam passes? Eventually you'll get a buildup that will block the beam.
Bog_Mire
2 / 5 (4) Apr 20, 2011
bit of kerosene and a wire brush.

kidding.
cmn
not rated yet Apr 20, 2011
What about fouling of the lens through which the laser beam passes? Eventually you'll get a buildup that will block the beam.

Spark plugs do as well... I'd imagine the laser version would be replaceable.
maxcypher
4.7 / 5 (3) Apr 20, 2011
What about fouling of the lens through which the laser beam passes? Eventually you'll get a buildup that will block the beam.

Perhaps the lasers could be mounted in the cylinder walls instead of the top so that the piston sealing rings constantly scrape/wipe them clean?
rethinker
1 / 5 (1) Apr 20, 2011
What about fouling of the lens through which the laser beam passes? Eventually you'll get a buildup that will block the beam.

Perhaps the lasers could be mounted in the cylinder walls instead of the top so that the piston sealing rings constantly scrape/wipe them clean?

seems logical and maybe part of the rings or as you say within a close proximity of the rings Chain saw manufacturing has self sharping why not self cleaning lasers

mrlewish
5 / 5 (4) Apr 20, 2011
Like the headline "Laser sparks revolution in internal combustion engines" Two double entendres in the headline.
Going
not rated yet Apr 20, 2011
The laser may well also blast away any coating of the lens.
Newbeak
1 / 5 (1) Apr 20, 2011
Who cares? Internal combustion engine are obsolete! Gasoline and diesel are obsolete! See wikipedia entry "energy catalyzer", or check out http://www.nickelpower.org

Almost certainly snake oil.See: http://www.popsci...kthrough
The Cyclone engine,however,is the real deal.I have been following it's progress for several years.I can't wait to see it applied to autos,power tools,etc
SemiNerd
not rated yet Apr 21, 2011
Long-term viability would have to be demonstrated too, engines are grimy, vibrating and hot, the lasers would have to tolerate these conditions for years without degrading in performance. That said, the benefits of cleaner burning fuel are more than enough reason to pursue this tech.

Nah... spark plugs have to be replaced every year or so anyway. It all depends on cost and how hard they are to replace.
Eco_R1
5 / 5 (1) Apr 21, 2011
@baudrunner ,then they have to shelf gasoline aswell for possible weapon production... empty beer bottle + gasoline + cloth + styrofoam = molotov cocktail.
rethinker
not rated yet Apr 21, 2011
gasoline is grandfathered in,so anyone who has some money can buy it,and as much as they want.
KnowledgeIsPower
not rated yet Apr 21, 2011
Gasoline engines are obsolete, like others have already mentioned. How about we release the magnetic zero-point motors and then we can talk about TRUE future technology, that requires NO FUEL whatsoever?? Even in japan they have cars that run off of water! I think the "Laser igniters would be great for BBQ igniters!!
Ricochet
5 / 5 (2) Apr 21, 2011
I think the idea is that the explosion created by the lasers will require less fuel in the mixture, and a more complete burning, which would mean naturally less leftovers, and therefore less residue.
As for the claims that gas engines are obsolete, while technologically, they may be, they will only become "obsolete" once there's a new industry standard.
Ricochet
not rated yet Apr 21, 2011
In any case, I was thinking they'd make really neat model rocket launchers.
rethinker
1 / 5 (1) Apr 21, 2011
Gasoline engines are obsolete??

Most likely we will still see them used for the next 200 years.

If you want to get rid of any of your fleet,let me know I come and get them out of your way.
Newbeak
not rated yet Apr 23, 2011
Gasoline engines are obsolete??

Most likely we will still see them used for the next 200 years.

If you want to get rid of any of your fleet,let me know I come and get them out of your way.

Jeez,there better be something better in a lot sooner than 200 years from now.Think of the pollution from god knows how many ICE engines if we still used the technology a couple of hundred years from now!
If we still have combustion powered engines in the future,at least have them use external combustion,which can be made 100% complete.I'm thinking along the lines of the Cyclone engine.
Newbeak
not rated yet Apr 23, 2011
Gasoline engines are obsolete, like others have already mentioned. How about we release the magnetic zero-point motors and then we can talk about TRUE future technology, that requires NO FUEL whatsoever?? Even in japan they have cars that run off of water! I think the "Laser igniters would be great for BBQ igniters!!

You have to be skeptical in these matters.There is no serious published research in zero point energy being used as a power source.Similarly,cars cannot run on water.There are gadgets that produce hydrogen for injection into an engine,but the difference it makes in fuel economy is non-existent.Popular Mechanics tested them and found them to be useless.
Skeptic_Heretic
not rated yet Apr 24, 2011
So there are two problems with spark plugs that facilitate wear. The metal degrades over time leaving a larger gap, and combustion byproducts build up on the filaments insulating the gap.

How would they keep the laser emitters clean?
Newbeak
5 / 5 (1) Apr 24, 2011
So there are two problems with spark plugs that facilitate wear. The metal degrades over time leaving a larger gap, and combustion byproducts build up on the filaments insulating the gap.

How would they keep the laser emitters clean?

Good question.Perhaps the deposition of combustion byproducts wouldn't be as problematic if only extremely lean fuel mixtures were used..
k_m
1 / 5 (3) Apr 24, 2011
Maybe some people will remember the spark plug anti-fouling devices some installed on worn engines with excessive oil blowby. They were basically hollow tubes screwed into the cylinder head that the plugs screwed into. This removed the electrodes from direct exposure to combustion gasses.
A similar approach could be done with lasers: they could be recessed / removed away from the chamber and focus the beams within the chamber.
Newbeak
not rated yet Apr 24, 2011
Maybe some people will remember the spark plug anti-fouling devices some installed on worn engines with excessive oil blowby. They were basically hollow tubes screwed into the cylinder head that the plugs screwed into. This removed the electrodes from direct exposure to combustion gasses.
A similar approach could be done with lasers: they could be recessed / removed away from the chamber and focus the beams within the chamber.

That is new to me,but I'm not a mechanic.Perhaps a combination of anti-fouling devices and ultra-lean combustion would work.
totalloser
not rated yet Apr 24, 2011
I doubt that this technology will help with NOX emissions. Especially run at leaner mixtures. Oxides of nitrogen are created in a LEAN condition where normally stable nitrogen under high pressures and temperatures becomes unstable and in the presence of *excess* oxygen bonds with it.

Lean conditions generally also HARM efficiency. Gasoline engines gain efficiency and run cooler when run slightly richer of a stoichiometric mix.

A rapid ignition would mean later ignition timing and a flame front that would not be fighting the compression stroke. This could garner efficiency, though I'd wager less than 5%.
totalloser
not rated yet Apr 24, 2011
Anti fouling devices work in a completely different way. They increase the distance heat has to travel back to the engine head. This means that a longer path means a hotter plug. This heat burns off excess fouling.

"Hotter" plugs do the same thing by simply increasing the depth of the gap around the center electrode.
Ricochet
not rated yet Apr 29, 2011
How about two laser beams being shot into the cylinder from a "protected" distance, intersecting in the middle of the cylinder, whereas neither beam by itself is enough to cause an explosion of the fuel air cloud, nor cause damage to the cylinder housing, combined at the interection point to ignite the fuel...
KBK
1 / 5 (2) May 01, 2011
This is all about putting perfume on a pig... and besides, the oil companies have a history of killing innovation or any inventors/inventions that threatens their cash cow by being truly game changing.

Oil companies are tuly run by low or zero empathy sociopaths posing as humans.

In case you did not know, sociopaths really are out there in corporations in huge numbers-at the top. Their trick is that they learn to emulate emotions as children, as a protection/ hidden truth' issue and reasoning. The ones you seen in the prisons are the weaker, more foolish and lesser intelligent ones.

Look it up, no angry comments on this truth, please and thank you.

Dump the gasoline. Work on real technologies, not this.
Skeptic_Heretic
not rated yet May 02, 2011
In case you did not know, sociopaths really are out there in corporations in huge numbers-at the top. Their trick is that they learn to emulate emotions as children, as a protection/ hidden truth' issue and reasoning. The ones you seen in the prisons are the weaker, more foolish and lesser intelligent ones.

Look it up, no angry comments on this truth, please and thank you.
You mean psychopaths, not sociopaths. They're referred to as 'industrial psychopaths' and typically score in the mid 30's on the PCL.