Laser igniters to replace spark plugs

Laser igniters are set to revolutionise transportation by replacing spark plugs that have powered internal combustion engines for more than 120 years.

These low cost igniters, made from ceramics, will now provide cleaner, more efficient and more economical vehicles, says study author Takunori Taira of Japan’s National Institutes of Natural Sciences.

In the past, lasers strong enough to ignite an engine’s air-fuel mixtures were too large to fit under an auto hood.

Conventional spark plugs pose a barrier to improving fuel economy and reducing emissions of nitrogen oxides (NOx), a key component of smog, said Taira, according to the institute’s statement.

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. Conversely, lasers, which ignite the air-fuel mixture with concentrated optical energy, have no electrodes and are not affected.

Equally important, Taira 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.

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Lasers promise less pollution and greater fuel efficiency, but making small, powerful lasers has, until now, proven hard.

These findings will be presented at the Conference on Lasers and Electro Optics scheduled in Baltimore, US, in the first week of May.

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