Researchers at the University of New South Wales, Australian Defence Force Academy have created a powerful laser which can be used to ignite fuel for hypersonic scramjets while travelling at speeds up to Mach 10.
Dr Sean O’Byrne, lead researcher in the laser diagnostics group, and PhD student Stefan Brieschenk have proved that laser-generated sparks can ignite supersonic mixtures of hydrogen fuel and air. The successful demonstration occurred after three years designing and building the supersonic ignition experiment.
“At flight speeds of around 10,000km/h, one of the difficulties with scramjets is getting the fuel to mix and burn before the air has left the engine,” O’Byrne said.
Using the laser, the researchers have been able to create sparks at temperatures close to 100,000 degrees Celcius, under which hydrogen fuel forms a small amount of atomic hydrogen, accelerating the reaction between the fuel and the air, even at temperatures that are too low to spontaneously ignite. As each laser pulse only lasts for a few billionths of a second, the laser-generated spark requires less energy than a continuous electrical spark.
While it has been developed for application in hypersonics, it is expected that the same principle will have application in natural gas engines. “Natural gas is a fuel with a lot of potential for clean combustion, and the success of Stefan’s experiments indicate that this technique may also improve ignition from gas-fired engines,” said O’Byrne.