Lasers to replace spark plugs in zapping engines into running more efficiently
An internal combustion engine hummed away in a lab near Chicago for a week last November, and it brought a different kind of excitement. The reason for the excitement is due to the fact that this particular engine sets fire to fuel with lasers instead of spark plugs, burning fuel more efficiently than normal. Laser-ignited engines could lead to cleaner and 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. 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 pace 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 excellent instant for ignition. They can even be fired multiple times during the same cycle into different parts of the cylinder to maximize fuel burn.
The laser-fired engine was presented for the first time at the ARPA-e energy innovation summit last week in Washington DC. 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 generate.
"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."