X2 HEHC Rotary Engine Can Run Multiple Fuels, Requires No Cooling

The nature of the internal combustion engine is harnessing the power of thousands of small, controlled explosions. Alas, most of the energy created is wasted as heat, but a new rotary engine design can almost double the thermal efficiency of almost any kind of fuel while requiring fewer moving parts for a light, powerful, and simple engine design.

Called the X2 High Efficiency Hybrid Cycle engine, it is being developed by researchers at the U.S. Department of Energy LiquidPiston as a project aimed at making a more efficient combustion engine. Right now, most combustion engines can only achieve between 30 and 40% efficiency, which a majority of the energy created becoming waste heat. Today’s engines also have more valves, camshafts, and other complicated moving parts that make them heavy and costly to build.

The X2 HEHC engine combines the benefits of the four different kinds of combustion engines. The X2 has a high-compression ratio like diesel engines, the constant volume combustion of Otto cycle engines, the over-expansion to atmospheric pressure ala Atkinson cycle engines (commonly used in hybrids) and the internal cooling system using air or water of Rankine cycle engines.

What researchers have come up with is an engine that is quieter than current motors, delivers up to 58% thermal efficiency, and an extremely lightweight design that makes around 2 horsepower per 1 lb. of engine weight. Combined with fewer moving parts, it makes for a simple-yet-effective engine design that could lead to big fuel economy gains.

Researchers the world over are looking at new engine designs, from opposed-piston to wave disks to super steam engines. But none have tried to combine the benefits of the four different engine cycles into a single working unit. It’s a bold idea to be sure, one that would offer the world a cheap, lightweight engine that can run a multitude of different fuels.

There is currently a working prototype-grade version of the X2 engine, and researchers believe that they could get as much as 74% thermal efficiency from this engine design. This could triple the fuel economy of even the most efficient cars on today’s market. Imagine what that would do to oil prices and the automotive market. Sounds promising, but the X2 is still a long ways out. Will it ever move beyond the lab?

Source: Green Car Congress


Christopher DeMorro

A writer and gearhead who loves all things automotive, from hybrids to HEMIs, can be found wrenching or writing- or else, he's running, because he's one of those crazy people who gets enjoyment from running insane distances.