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Rotary engine spins comeback

Posted: 01 Feb 2007 ?? ?Print Version ?Bookmark and Share

Keywords:Wankel? rotary engine? Regi U.S.? Radmax? automotive?

Remember the Wankel? There's a new twist on the rotary engine whose quirky name once made it fodder for a Monty Python sketch.

Conceptualized by German inventor Felix Wankel in the 1920s, the Wankel engine rolled into the North American car market in the 1970s, but made little headway. Now, a Canadian company says it has fine-tuned the design and is preparing to reintroduce the technology to a broader market that includes the U.S. military.

Reg Technologies Inc. says that its Radmax direct-charge engine is based on the Wankel rotary design, but can deliver up to three times the power with half the weight of a true Wankel engine of the same size. "It's a very simple design, so it's very efficient," said John Robertson, president of the engine company, which shares the rights to the Radmax technology with subsidiary Regi U.S. Inc.

The fundamental difference between the rotary design and standard reciprocating piston engines is that the intake-compression-ignition-exhaust sequence is completed in one revolution rather than two. That makes the rotary design more fuel-efficient.

While the company has discussed licensing deals with automakers, including an unidentified electric-car maker that might use the technology for battery recharging, its best customer opportunity may be the U.S. military. Licensee Radian Milparts has built a four-stroke, 42HP diesel engine based on Radmax technology to power unmanned air vehicles. The key to the application is weight: Since the engine is lighter and more fuel-efficient, unmanned aircraft could carry less fuel but fly longer.

The company is also pitching the technology to makers of hybrid autos for use in generators to recharge electric engines. It is designing diesel engines for possible use in other military vehicles. And a prototype 125HP diesel engine has been built, with variations targeting everything from battery chargers and air-conditioner compressors to golf carts and hybrid electric cars.

Wankel's downfall
The Wankel engine design was indeed revolutionary. Its downfall, according to Robertson, was that the engine was insufficiently sealed to prevent fluids from leaking and to control emissions. Robertson's company claims to have solved the problem through an innovation it calls flat-surface sealing. The technique eliminates corners, making it easier to seal engine components such as combustion chambers.

Unlike a reciprocating piston-driven engine, Robertson notes, the Radmax design provides "constant combustion." He likened the engine's performance to riding a bike downhill, whereas a piston engine's operation is analogous to pedaling uphill.

The Wankel that made the Mazda hum gets an overhaul for duty in unmanned military aircraft.

In the Radmax design, a disk-shaped rotor and drive shaft turn a circular housing. Up to 12 vanes, substituting for pistons, are mounted parallel to the shaft to help form combustion chambers. A 20:1 compression ratio means the engine can burn a variety of fuels, including natural gas, hydrogen, propane, diesel or regular gasoline.

The company is gearing up for comprehensive testing of the second-generation rotary engine as soon as early this year. It is also seeking partners to help it build engines if and when the orders roll in. The company claims to be close to a deal with automotive-component maker and military contractor Etco Inc.'s automotive products unit.

Promising technology
At least one analyst thinks the technology is promising and that the new engine design could tap into a global market estimated to be worth as much as $200 billion.

Market researcher Bridge IR Group released a research report in November highlighting weight, power and fuel-efficiency advantages for the Radmax design in a wide range of applications. With several prototypes already in testing, Bridge concluded, Radmax's developer could quickly move to production and "achieve commercial success."

As the failure of the first Wankel engine showed, however, the global auto market is littered with good ideas that came to naught. Industry observers said the company's chances for success depend on its ability to sell Radmax engines to a variety of customers beyond automakers.

Reg Technologies has spent $11 million on Radmax engine development over the past several years. "We see light at the end of the tunnel," Robertson said.

Asked whether the company is trying to raise money beyond the equity line of credit it announced in November, Robertson responded, "We wouldn't turn it down."

- George Leopold
EE Times

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