The go-kart's conventional piston engine is on the left, the LiquidPiston rotary alternative is on the right
A new kind of engine has showed its stuff for the first time outside the lab, and though it merely made a go-kart go, it could well be the start of something big.
The engine is a rotary design, a pistonless setup that maximizes the power-to-weight ratio. It’s the fruit of a dozen-odd years of work by LiquidPiston, a startup co-founded by Alec Shkolnik, who has a Ph.D. in computer science, with a specialization in AI and modeling. The engine itself is based on combustion technology developed by his father, Nikolay, a Soviet-trained mechanical engineer who retrained in the United States as a physicist.
There’s no liquid, though, and no piston: The company has outgrown a name that referred to a design that used both to convert expanding gas into propulsive force. Now, half a dozen iterations later, the result is an all-metal rotary engine that’s decidedly not your father’s Wankel, the famous, humming heart of the Mazda RX series.
“It’s kind of a Wankel flipped inside out, a design that solves the old problems with sealing and fuel consumption,” says company founder Alec Shkolnik. “The Wankel has a triangular rotor inside a peanut-shaped housing; we have a peanut-shaped rotor inside a triangular housing. Our seals go at the apexes of the triangle [...] and our seals are stationary because they’re in the housing.”
The seals stop gas from moving from one chamber to another. In a Wankel, the seals move rapidly, and that makes them hard to lubricate. You have to spray oil into the combustion chamber knowing that only a fraction will reach the seals and the rest will go up in smoke—a problem for both fuel economy and engine emissions. LiquidPiston’s engine lacks that baggage but retains the rotary engine’s intrinsic mechanical simplicity—just a rotor and an eccentric shaft, together with fuel injectors, fuel pumps and oil pumps.
Shkolnik admits that his machine is hardly ready yet for the auto industry’s 100,000-mile durability standard. But he argues that even in its teething stages it should find application in any field that prizes a tiny, fuel-efficient simple motor that packs a lot of power into a small volume and mass.
“We’ve replaced the go-kart’s 40-lb engine with our 4-lb, 3 to 5 horsepower engine,” Shkolnik says. As of today, you can buy the developer’s kit.
It will be interesting to see if they can scale up this design to what is needed for an automobile. A 20lb prime mover cranking out 35 hp in a hybrid would solve a lot of engineering problems.