A Practical Detonation Engine.

Exploding Engine Could Reduce Fuel Consumption
The military and GE have made strides toward a practical detonation engine.

          A new kind of engine under development, called a detonation engine, could save the military hundreds of millions of dollars in fuel costs every year. The technology, which military researchers are working on together with scientists at GE and other companies, could reduce fuel consumption at power plants, in ships, and on airplanes by as much as 25 percent. The Navy alone estimates that retrofitting its ships with the technology would reduce annual fuel costs by $300 to $400 million.

It could be over a decade before such engines are put to practical use. But DARPA, having finished detailed plans, is now in the middle of a $62 million program aimed at building the first full-scale demonstration of one version of the technology. (GE is involved in the project: see “GE’s Risky Research.”) Meanwhile, Navy researchers are using sophisticated simulations to advance a version of the concept that could make it far more practical.

Detonation engines would replace jet engines in airplanes and the gas turbines that run power plants and Navy ships. A set of rotating blades at the front of those engines compresses air, which is then mixed with fuel and combusted in a steady flame. That produces hot gases that do the work an engine is designed to do, whether it’s turning a propeller, propelling a jet, or spinning a generator to produce electricity.

Improving the efficiency of conventional jet engines has involved finding ways to increase air compression. But the cost and complexity of that approach is making it harder to realize improvements. Detonation engines offer another way to achieve high pressures. In a detonation engine, fuel combustion generates a shock wave that raises pressures to levels 10 times those inside a conventional engine. “It’s like an explosion or a bomb,” says Kazhikathra Kailasanath, a researcher at the Naval Research Laboratory in Washington, DC. “If you burn something in an open flame, the pressure stays the same as the surrounding pressure. The big difference with a detonation engine is going from that to a confined type of combustion, where the pressure goes up and the combustion occurs more rapidly.”

The most highly developed form of detonation engine, which has been in the works for many years, is the pulse detonation engine, the type GE is developing. Whereas combustion occurs continuously in a conventional jet engine, pulse detonation involves setting off a series of detonations—say, 60 to 100 per minute.....

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