Laser ignition demonstrated in a real engine could boost engine efficiency by 27%

Spark plugs can only ignite the fuel at one end of the chamber. 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 miles per gallan up to around 50 miles per gallon, for example. The more complete burn emits fewer polluting by-products such as nitrogen dioxide. New Scientist reported on an ARPA-e energy innovation summit presentation

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.

Princeton Optronics is the first to show that it works in a real engine.

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.”

Nature Photonics in 2008 had another study on laser ignition for engines.

A new ignition concept is needed for lean-burn combustion in gasoline engines. The approach should extend the lean ignition limit air/fuel ratio to greater than 20, to enable reliable ignition under high in-cylinder pressures (up to 100 bar at the time of ignition) thus enabling high load operation, operation under high levels of exhaust gas recirculation, and lower or maintain ignitability (coefficient of variance of IMEP less than 3%). The objectives of phase I would be to develop a laser igniter for advanced automobile engines. Our goal would be to first define the specifications of the laser igniter to be developed. We would then design and build a laser igniter in and test it very thoroughly at Argonne National Laboratory. The major objectives of testing will be determining optimal laser pulse energy, number of pulses required per combustion cycle, time spacing between pulses, thermal load in the spark plug well, and other such parameters through single-cylinder engine tests. In phase II, we would develop a more advanced laser igniter and test it thoroughly for all the relevant parameters. In phase I, we would first define the specifications of the laser igniter to be developed in phase II of the program. We would then design the laser igniter to be developed in phase I and order the of the optical, mechanical and thermal components. Next we would do the optical bench test and verification of the solid state laser design and build the the laser ignition module. We would then test the laser igniter in a single-cylinder engine at Argonne National Lab. Finally, we would do the design for the improved laser igniters to be built in phase II. Commercial Applications and Other Benefits: The laser igniters would have near term high volume applications in automobile engines. In addition to automobile engines, it will have applications in natural gas power generation engines and other types of power generation engines such as those using biogas. In future it will have applications for natural gas truck engines and aerospace engines.

Princeton Optics is working on Improved Reliability Laser Based Ignition System

Navy needs improved reliability ignition systems for aerospace engines to reduce flameouts at high altitudes as well as reduce maintenance cost because of the need to frequently replace the conventional spark plug igniters for fuel ignition in the engines. Laser ignition, whose feasibility has been demonstrated in the past decade for conventional natural gas and gasoline engines is very well suited for ignition in the aircraft engines. They would be very reliable and would reduce the spark plug related repairs needed for the aircraft engines. They would also reduce engine flameout and reduce the relight time for the engines, improve the fuel efficiency and reduce the NOx emissions. The new technology of high power VCSEL pumps and VCSEL pumped solid state lasers developed at Princeton Optronics is finding application towards laser spark plugs for automobile and natural gas engine applications. Princeton Optronics wants to use this technology to make laser ignition systems for aerospace engines. In phase I, the feasibility of the approach will be studied and in phase II a prototype will be built and tested.