Faster than supersonic on ‘spiked’ jet fuel

PRINCETON (US)—A team of engineers is testing fuel additives made from tiny particles called nanocatalysts that may allow supersonic jets to fly faster and cleaner.

The nanocatalysts are composed of snippets of carbon sheets only a single atom thick.

“Right now we don’t know what actual reactions enhance the combustion rates when the particles are added to fuels,” says Ilhan Aksay, a professor of chemical engineering at Princeton University and the project’s lead investigator. “If we understand it further, we can make it more effective.”

The researchers are hoping to tackle a basic barrier to designing faster supersonic aircraft. The ignition time and burn rate of current jet fuels limits the speed of the engines.

“To fly at highly supersonic speeds one needs to run the propulsion system at supersonic speed to maximize its efficiency, but there is little time to mix, ignite, and extract energy from the fuel,” explains Richard Yetter, a professor of mechanical engineering at Pennsylvania State University and a principal investigator on the project. “To make the planes go faster, we need to burn fuel faster.”

The Princeton-led team has proposed a solution based on the use of graphene—molecular sheets of carbon atoms that exhibit unusual physical and electrical properties.

In 2003, Aksay and his chemical engineering colleague, Robert Prud’homme, developed the first commercially viable technique for making graphene by using a chemical process to split graphite into its ultrathin individual sheets. The resulting flakes are 200- to 500-nanometers wide, making the largest of them about one-hundredth the width of an average human hair.

Aksay and his colleagues are hoping to leverage another characteristic of the graphene particles: When small amounts are added to liquid fuels, they lower the temperature at which the fuel ignites.

“The concentration of the nanocatalyst in the fuel would be very small,” Aksay says. “The idea of being able to put in a very small quantity and have such a dramatic effect is important.”

The catalyst also might be used to reduce the amount of nitric oxide produced by diesel engines or accelerate soot oxidation rates, which may reduce pollution and fuel use. The graphene particles could even be used in liquid propellants for thrusters that help satellites position themselves in space.

Researchers from the University of Delaware, Stanford University, and the University of Maryland contributed to the study. The work is funded by a $3 million grant from the U.S. Air Force.

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