“Inside-out Wankel” rotary engine delivers 5X the power of a diesel

Intended for military, commercial and aerospace applications, the XTS-210 is about the size of a basketball, weighs 19 kg (42 lb) and displaces 210 cc. It will run on multiple fuels including diesel and kerosene/jet fuel. The company is aiming for around 20 kW (26.8 hp) and 29.4 Nm (21.7 lb-ft) of torque, both at 6,500 rpm.

Those numbers compare favorably to the 18.8 kW (25.2 hp) and 63 Nm (46 b-ft) peak outputs of the Kohler KDW1003 E536A, according to LiquidPiston, a diesel about five times larger than the XTS-210, and more than four times the weight. And the XTS design uses only two major moving parts: a rotor and a shaft. You can see a breakdown of an older version in the video below.

So how do they work? “If you remember the Wankel,” LiquidPiston co-founder and CEO Alec Schkolnik told us in a interview 2020“they have a triangular rotor inside a peanut-shaped case. We have the opposite, a peanut-shaped rotor in a trilobal case. So take everything you know about the Wankel and flip it literally.

“They have a long, thin, movable combustion chamber, we have a stationary combustion chamber that’s nice and round. You can drive it to high compression, just by reducing the chamber. And because it’s stationary, we can directly inject fuel where the Wankel could not. So these are the two main advantages of diesel: high compression ratio and direct injection.

“And then there are our apex seals, they are like our piston rings. In the Wankel engine they are inside the rotor again. In our case, they are fixed, they do not bounce and you can lubricate them directly from the housing.

“So we’ve basically solved the major problems that older rotary machines had with regard to combustion and lubrication. These lubrication problems have caused both durability problems and emissions problems. By making these components fixed, we’re solving the challenges of the old rotary. And we also improved its cycle to give it much higher efficiency.”

LiquidPiston X-Engine takes flight [Long]

LiquidPiston has been working on these X engines for almost 20 years now, with many prototypes already tested in small planes (see above) and karts. Other prototypes have included naturally aspirated versions developing up to 40 hp and forced induction engines up to 70 hp. They performed these things on diesel, gasoline, hydrogen And propaneand they are currently developing the XTS-210 with JP-8/Jet-A fuel due to its ubiquity in defense and aerospace.

The company is set to commercialize the XTS-210 based on a $9 million contract with the U.S. military, with a prototype slated for delivery in 2024. This brings LiquidPiston’s military contract total to over $30 million. Its immediate use cases are expected to be in portable generators and UAVs, although a separate project is evaluating it for use in a hybrid-electric VTOL UAV.

“There are virtually no diesel engines in the 25 horsepower class today that are suitable for mobile aerospace and military applications, where size and weight parameters are particularly critical,” Shkolnik said in a statement. Press. the heavy fuel or multi-fuel capability of the XTS-210 provides significant end-system capability and utility benefits, especially for the military to reduce supply chain and logistics loads in an era of “power in motion” is increasingly important. »

The XTS-210 is about the size of a basketball and produces around 25 peak horsepower

Liquid Piston

As electrification takes off, it’s difficult to work on new combustion engine concepts – but the military certainly won’t be all-electric anytime soon, and the portability and multi-fuel capability of the LiquidPiston design certainly could take it to volume manufacturing if it proves to be effective and durable under a wide range of conditions.

Source: Liquid Piston

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