Posted on 08/12/2003 5:39:38 PM PDT by Brett66
After Combustion:Detonation!
At first glance, the engine bolted to the test stand looks like an unlikely candidate to lead an aerospace revolution. Its size is unimpressive: At about four feet long, it's dwarfed by the machinery that feeds it air and fuel, machinery that fills a house-size structure at the China Lake Naval Air Warfare Center in California. And its appearance is unremarkable: This machine has none of the grace of the high-bypass turbofans that power modern jetliners, with wide, sweeping inlets and delicate blades. From the outside, it's simply a collection of metal tubes, one large cylinder feeding into five smaller ones terminated by convex, barnacle-shaped nozzles.
But Gary Lidstone and Tom Bussing have bet that this little aircraft engine—the most advanced expression yet of a revolutionary concept called pulse detonation—could absolutely bury all those that have come before it. Lidstone is the manager of propulsion programs for Pratt & Whitney's Seattle Aerosciences Center, and Bussing is his boss and the creative force behind the device's design. Here at China Lake, standing in the desert heat, the two survey their handiwork like proud papas, explaining how it has taken years to show that the concept behind this engine can open up an entirely new world of jet propulsion. "There's a big payoff," Lidstone says. "It's a paradigm shift that could make other things obsolete."
Indeed, Lidstone's team is hardly alone in its quest. In the past 10 years, the promise of the technology—a promise of a propulsion system far simpler than today's turbofans and capable of operating across a much wider velocity range, powering aircraft from takeoff to Mach 4 with ease—has touched off an explosion of interest at university, military and NASA research centers, and in labs as far away as Japan, France and Russia. In just the past three years, the two companies that stand to gain or lose the most from the rise of a revolutionary, market-disrupting jet-engine technology have begun to invest heavily in pulse-detonation engine (PDE) research. In January 2001, Pratt & Whitney bought the company Bussing had created to develop his concepts. That same year, General Electric designated pulse detonation a top priority. Arriving late in the game but armed with a new approach that could trump Pratt & Whitney, GE began plowing resources into building a PDE development team at its Global Research Center in upstate New York. "We see pulse detonation throughout our entire product line," says Harvey Maclin, manager for advanced technology, marketing and government programs at GE Aircraft Engines and one of the early sponsors of pulse-detonation research at GE. "That's why we're so interested in it."
For decades, these two companies have been battling for supremacy in the global jet-engine arena, exploiting any advantage that might give them an edge in the struggle for civilian and military market share. But those advantages have grown smaller as conventional jet-engine performance edges closer to the limits of thrust-to-weight ratios and fuel efficiency. Pulse-detonation technology offers a chance to escape from this spiral of diminishing gains and score a big win—not to mention the first lucrative corporate and military contracts. Those contracts could be for superefficient engines for subsonic jetliners, which would chop fuel consumption by an amount that engineers would "kill their grandmothers" to get, Lidstone jokes, or for supersonic, unmanned aerial vehicles or manned fighters. We could also see a supersonic airliner that's much cheaper and more practical than the recently grounded Concorde. Pulse detonation would also offer cheaper access to space, saving tons of liquid oxygen and fuel by powering vehicles from the ground to high altitude and hypersonic velocity, where conventional rocket engines would take over to lift them into orbit.
1st of six parts:
PULSE DETONATION: HOW IT WORKS
(Top) Pure PDE. Pulse-detonation engines use a more efficient combustion process, a detonation wave, to produce power. In a pure PDE, a spark ignites a tube filled with an air-fuel mixture (top). The explosion travels supersonically down the tube (center), blowing exhaust gases out the end and sucking more air and fuel inside.
(Center) Conventional turbofan. Jet engines produce power in two ways: A central combustion area creates a large amount of thrust but isn't efficient for long trips. For that, a turbine powers a fan, which blows air around the combustion chamber and out the back. The fan is efficient at subsonic speeds, but is unsuitable for long supersonic flights.
(Bottom) Hybrid PDE. A hybrid turbofan-PDE would combine both systems: The central core engine would still turn the large fan in front, but the bypass air would flow into a ring of PDEs. This system would produce significantly more thrust without requiring additional fuel.
Illustrations by Stephen Rountree
Refrigerators, toasters, blenders, and VCRs.
That was my first thought...
"Pulse-conflagration" would be the proper description. The pressures and therefore efficiency of detonation is orders of magnitude higher.
The latest "Popular Science" edition has an in depth analysis of the "PDE".
Possible PDE contrail
Bill Richardson eating
a) Theoretically the pulse jet engine has a higher fuel efficiency than a normal jet engine that keeps constant pressure. Intermittent rather than constant fuel combustion is another key factor in making the pulse-jet engine more fuel efficient. than ordinary
b) Engines can be produced in many sizes with many different thrust outputs ranging from a few pounds to thousands of pounds.
c) They have a very high thrust-to-weight ratio, which means a lighter engine producing more pounds of thrust than it's weight.
d) They are mechanically very simple and have very little moving parts.
The tubes are closed at one end, unlike a Ram-jet.
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