Lasers set to zap engines into running more efficiently

[Nipuna]

Vital spark: room for improvement (Image: Horizon International Images Limited/Alamy)

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PEW pew! For a week last November an internal combustion engine hummed away in a lab near Chicago. Why the excitement? This particular engine sets fire to fuel with lasers instead of spark plugs, burning fuel more efficiently than normal. Laser-fired engines could lead to cleaner, greener cars.

In a normal combustion engine, a mix of fuel and air enters a chamber where it is ignited by a spark plug. Hot, expanding gases from the burning fuel then exert force on a moving part such as a piston – generating mechanical energy that can be used to turn the wheels of a car, for example. But because each combustion cycle happens very quickly, it is hard to get all of the fuel mixture to burn. The problem is that spark plugs can only ignite the fuel at one end of the chamber, says Chuni Ghosh, CEO of New Jersey-based Princeton Optronics, the firm that developed the new ignition system.

In Ghosh's engine, a laser ignites the fuel in the middle of the chamber instead, burning more of the fuel and improving combustion efficiency by 27 per cent. Laser ignition could boost the fuel efficiency of a car from 40 kilometres per litre up to around 50, for example. The more complete burn also emits fewer polluting by-products such as nitrogen dioxide.

Lasers are also better at keeping up with the thousands of cycles a minute at which a car engine runs. They can be tuned more precisely than spark plugs so that they fire at the optimal instant for ignition. They can even be fired multiple times during the same cycle into different parts of the cylinder to maximise fuel burn.

The engine was presented for the first time at the ARPA-e energy innovation summit last week in Washington DC. The idea itself is not new, but Princeton Optronics is the first to show that it works in a real engine, with the heat and extreme forces that thousands of revolutions per minute produce. Toyota toyed with a similar system in 2011, but never tested it in these conditions.

Cars are not the only vehicles that stand to gain. Back-up generators and ships' engines could benefit too. "There is a lot of pressure on the shipping companies to reduce the pollution from their ships," says Ghosh. "One shipping company we are talking to is interested in retrofitting their existing engines with laser ignition."

This article appeared in print under the headline "Lasers set to stun engines into efficiency"