External combustion engine

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External Combustion
U.S. Military Looks Into Clean-burning Cyclone Engine
By william matthews
Published: 4 May 2009
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A bit more than a year ago, as oil prices climbed, two of the Big Three automakers were keenly interested in Harry Schoell's Cyclone external combustion engine. Then the auto industry collapsed.

Today, two of another big three are eyeing the Cyclone engine. The U.S. Army thinks it may be an efficient way to generate electricity. The U.S. Navy sees a new way to propel torpedoes.

Schoell, a Florida inventor, envisions a day when his external combustion engine replaces most of today's gasoline- and diesel-powered internal combustion engines.

Its advantages are many, Schoell says. It's smaller, simpler, cleaner, quieter, more economical and it can be fueled by almost anything that will burn.

"It's far superior," he said.

But it's hard to convince a world in the tight embrace of a 100-year love affair with the internal combustion engine. Schoell hopes to start by convincing the U.S. military.

The Cyclone engine works by pumping fuel and air into a round combustion chamber, where it swirls cyclonelike and burns at about 2,000 degrees Fahrenheit. Combustion gas passes into a heat exchanger, where it heats deion-ized water to 1,200 degrees under 3,200 pounds of pressure.

The water turns into steam, but under pressure the steam remains in a fluid state and is referred to as a "supercritical fluid," Schoell said.

The steam passes through a valve and into a cylinder, where it expands with almost explosive force to drive a piston. When the piston is pushed to the far end of the cylinder, the steam exits through an exhaust port.

From there, the steam enters another heat exchanger, where heat is recovered and cycled back to the combustion chamber. Now cooler, the steam exits the heat exchanger and enters an air-cooled condenser, where it is turned back into water and is pumped back to the first heat exchanger to go through the cycle again.

The process for turning water to steam and back is a closed cycle. The engine needs fuel to produce heat to make steam, but virtually any fuel will do. Schoell has run his engines on gasoline and diesel fuel, but also on fuel made from orange peels, palm oil and chicken fat.

Propane gas will work, and so will ethanol, biofuel, powered coal, municipal garbage and agricultural waste, Schoell said.

"We can run it on dirty oil drained from a crankcase," he said. "Nothing will harm the engine."

And the cyclonelike swirl of fuel and air in the combustion chamber enables complete combustion so there is little except carbon dioxide as exhaust. The Cyclone engine emits almost none of the unburned hydrocarbons, carbon monoxide and nitrogen oxide that come from an internal combustion engine.

No Lubricant Needed

The deionized water - water that is highly filtered to remove impurities - serves as the engine's lubricant as well as its source of steam, eliminating the need for oil, oil pumps or oil changes, Schoell said.

There is no radiator, no need for computers to control fuel mixtures, no catalytic converter and, even when used as a car or truck engine, no transmission.

Schoell, who founded Schoell Marine in 1966, has spent 40 years developing advanced boat hull designs and inventing marine propulsion systems. He began work on the Cyclone engine in 2004 and established Cyclone Power Technologies in Pompano Beach, Fla., to develop it.

The engine won awards from the Society of Automotive Engineers in 2006 and 2008 and was Popular Science magazine's invention of the year in 2008.

Much of the work of marketing the engine is being done by Advent Power Systems in nearby Coconut Creek, Fla.

Chief Executive Phillip Myers, a former Air Force engineering officer, touts the Cyclone's ability to run on multiple fuels as a solution to the military's "enormous logistical problem of providing multiple specific grades and types of fuels" for different vehicles, generators and other internal combustion engines.

Myers said the Army's Tank-Automotive Research, Development and Engineering Center is interested in a small Cyclone engine to power an electric generator inside its Abrams tanks, Strykers and Bradley fighting vehicles.

A 12-by-12-by-17-inch engine and generator would be used to keep electrical equipment in the vehicles going when the main engine is turned off. That would be a big gas saver for the Abrams, which has a 1,500-horsepower gas turbine engine that burns 12 gallons of fuel an hour simply idling.

In February, Cyclone Power Technologies announced the completion of tests with Raytheon of a Cyclone engine designed for the Navy to use in unmanned underwater vehicles and torpedoes. The engine burns Moden fuel, a liquid fuel that the Navy describes as low-cost and environmentally friendly.

The fuel contains its own oxygen, so it is able to burn in the absence of air, such as underwater and in space, Myers said.

Since they are lighter and smaller than internal combustion engines, Cyclone engines might also win favor as engines for propeller-driven UAVs, Myers said.

And the Defense Advanced Research Projects Agency (DARPA) is studying whether a Cyclone engine fueled by biomass could power robots on long-endurance military missions. DARPA's idea is that the robots would refuel themselves by foraging for fuel.

The robot would gather wood, grass, paper and other biological material, shred it and feed it into its Cyclone engine, which would power a generator to produce electricity to run the robot.

With DARPA-esque humor, the robot is dubbed an Energetically Autonomous Tactical Robot, or EATR. It is being developed for DARPA by Robotic Technology, Potomac, Md.

Robert Finkelstein, Robotic's president, said the Cyclone engine "looks very promising. It is better than what we were originally contemplating," which was a Sterling engine that uses temperature differences between cylinders to generate power.

A Cyclone modified to burn wood chips and other biomass is to be delivered to Robotic Technology this summer.

After seeing Cyclone engines in operation at Schoell's plant, Bilal Ayyub said he was convinced enough of the technology to place a six-figure order for the EATR engine. Ayyub is a University of Maryland engineering professor also working on the project. ■