The U.S. Air Force Research Laboratory is progressing with development of the Meyer Nutating Engine, a new type of internal combustion engine aimed at UAVs and other applications, with higher power density than conventional reciprocating piston engines.
The core of the concept - a nutating disk. (Guy Norris)
At the heart of the engine are two disks that nutate, or wobble, on individual Z-shaped power shafts. As the disk edges pitch up and down they create voids that increase and decrease in volume as they spin. The voids take the place of combustion chambers in the cylinders of conventional piston engines. The motion of one disk produces a four-stroke cycle, and enables the displaced volumes to be used twice per engine revolution, making the engine twice as power dense as a conventional two-stroke engine and four times as power dense as a four-stroke piston engine. One disk acts as an expander, and one that acts as a compressor. The disk directly drive shafts for propulsion or power generation. It also has the capability of changing compression ratios, and can use different fuels, including hydrogen, as well as heavy JP-8.
Working with Illinois-based Kinetic and BEI of Michigan, AFRL has successfully tested a prototype engine which, despite weighing only 103 lbs and being a mere 21.5 in long and 11.8 in wide, generates up to 150 Hp. AFRL program manager Gary Smith says the engine is “potentially capable of 230 Hp – it is running very de-rated.”
Development work is moving forward to new phases of experimentation, including more complete understanding of the combustion process. “We’ve got to write the book on nutation as nobody has done it before,” says Smith.
Darpa is also working with AFRL on the initial stages of a nutating auxiliary power unit for the General Atomics MQ-9 Reaper UAV. The target is a 5kW unit weighing just 16 lbs.
AFRL’s Gary Smith explains the basic concept of the Meyer Nutating Engine. (Guy Norris/YouTube)