Lasers Could Replace Spark Plugs, Making Engines More Efficient

The spark plugs driving combustion in your car may soon be getting an optical upgrade, thanks to a team of Japanese researchers. Laser ignition systems, which are exactly what they sound like, could replace spark plugs as the primary means to ignite the fuel-air mix in engines, boosting fuel efficiency and cutting down on carbon emissions.

In a conventional combustion engine, the fuel-air mix is compressed by a piston and ignited by a spark plug seated in the top of the cylinder. That spark is generated by electricity arcing between two electrodes, which is a good enough way to ignite fuel but also limiting in what kind of fuel you can burn.

With spark plugs, the fuel-air mixture has to contain a certain amount of fuel, otherwise the spark won’t ignite it. A hotter spark will ignite leaner fuel-air mixes (mixtures with more air, less fuel), but hotter sparks will also degrade the electrodes. An ideal engine would run on leaner fuel and supply a hotter spark, and that’s where lasers can deliver. And hotter ignition is just the beginning.

Laser ignition can be finely tuned to be more precise than spark plugs as well. If you were to slow down the four-stroke cycle you would see that the exact timing of the spark plug ignition is erratic and difficult to predict. Laser could provide better timing, making the combustion more efficient and improving overall economy.

Further, lasers can be focused to provide ignition anywhere in the cylinder (spark plugs generate their ignition at the top, opposite the piston). Laser ignition could focus the ignition in the center of the compressed fuel-air mix, allowing the controlled explosion to spread out more evenly within the cylinder, deriving even more bang from each stroke. Laser can even ignite the fuel in two places simultaneously, creating an even more efficient explosion.

Previously lasers with the power to do all of this were possible but unfeasible. They were large, unwieldy, and unstable. But new high-powered ceramic lasers developed by the Japanese team are just 9 millimeters in diameter and capable of the finely tuned nanosecond-duration blasts necessary for precision engine timing. Until we figure out that whole smart grid/hydrogen economy thing, laser ignitions could go a long way toward trimming fuel costs and otherwise making conventional engines more carbon efficient.

The Register