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LiquidPiston X-engine new rotary engine concept is awarded a US Army research contract


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May 9, 2008
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Connecticut-based company LiquidPiston is developing a portable generator for the US Army that uses its X-Engine, a new type of rotary engine that'll deliver as much power as the Army's current-gen-set at one-fifth the size.

The engine is a non-Wankel rotary engine.

View: https://vimeo.com/64911927

Article in NewAtlas with more detail

"If you recall the Wankel," says Schkolnik, "they have a triangular rotor inside a peanut-shaped housing. We have the opposite, a peanut-shaped rotor in a tri-lobed housing. So take everything you know about the Wankel and turn it literally inside out. They have a long, skinny, moving combustion chamber, we have a stationary combustion chamber that's nice and round. You can drive it to a high compression, just by making the chamber smaller. And because it's stationary, we can directly inject fuel where the Wankel could not. So those are the two key advantages of the diesel: high compression ratio and direct injection.

"And then there's our apex seals, they're like our piston rings," he continues. "In the Wankel engine, they're inside the rotor, again. They move at a high speed, and bounce around, they're very hard to lubricate. In our case, they're stationary, they don't bounce around, and you can lubricate them directly from the housing.

"So we basically solved the key challenges the old rotaries had with combustion and with oiling. Those oiling challenges caused both durability issues and emissions problems. By making those components stationary, we solve the challenges of the old rotary. And we also upgraded its cycle to give it much higher efficiency."

The X-Engine's ability to eliminate bulk and weight is extraordinary; to give you an idea, the team pulled a 40-lb (18-kg), 6.5-hp engine out of the go-kart in the video above, and replaced it with a 4.5-lb (2-kg) X-Engine making 3 hp.

LiquidPiston demonstrated the technology for the US Army by building a Compact Artillery Power System (CAPS) generator unit designed to power the digital fire control system on an M777 Howitzer artillery piece. It replaced a generator that needed a truck to move it around with something 20 percent the size: a 41-lb (18.6-kg), 1.5-cubic foot (28.3-L) box about the size of a gaming PC that can easily be carried by two men.