[SEL] Spark Plugs are becoming Obsolete

[Mark Shulaw]

Read an interesting article today in one of the 
newsletters I get. This idea has been around for 
a while but they are finally getting it near 
practical for automotive use. My bet is this idea 
originated here and we as usual did not pursue 
the research as it was deemed practicality was 
too distant in the future to be of immediate 
value to stock holders.  But this should interest 
this group. See the article below with credits.     Mark




Laser Sparks Revolution in Internal Combustion Engines

New laser system may lead to reduced auto emissions, enhanced fuel efficiency

WASHINGTON, April 20­For 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 
(<http://www.cleoconference.org/>CLEO: 2011), to 
be held in Baltimore May 1 - 6, researchers from 
Japan will describe the first multibeam laser 
system small enough to screw into an engine's cylinder head.
Laser Sparks



A standard spark plug (left) and the micro-laser 
with three-beam output for multi-point ignition 
(right). Photo courtesy Takunori Taira, National 
Institutes of Natural Sciences, Japan.

Equally significant, the new laser system 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 nitrogen oxides (NOx), a key component of smog.

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 cylinder­producing 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 fuel economy,” 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 ceramic 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.

This work is supported by the Japan Science and Technical Agency (JST).

CLEO: 2011 presentation 
<http://cleo2011.abstractcentral.com/planner?NEXT_PAGE=ITINERARY_ABS_DET_POP&SESSION_ABSTRACT_ID=797739&ABSTRACT_ID=1042779&SESSION_ID=83094&PROGRAM_ID=2916>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.

About CLEO
With a distinguished history as the industry's 
leading event on laser science, the Conference on 
Lasers and Electro-Optics (CLEO) and the Quantum 
Electronics Laser Science Conference (QELS) is 
where laser technology was first introduced. 
CLEO: 2011 will unite the field of lasers and 
electro-optics by bringing together all aspects 
of laser technology, with content stemming from 
basic research to industry application. Sponsored 
by the American Physical Society's (APS) Laser 
Science Division, the Institute of Electronic 
Engineers (IEEE) Photonics Society and the 
Optical Society (OSA), CLEO: 2011 provides the 
full range of critical developments in the field, 
showcasing the most significant milestones from 
laboratory to marketplace. With an unparalleled 
breadth and depth of coverage, CLEO: 2011 
connects all of the critical vertical markets in 
lasers and electro-optics. For more information, 
visit the conference's website at 
<http://www.cleoconference.org>www.cleoconference.org.

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