Machine Design

Rotary engine burns diesel

The RandCam Direct Charge engine is an internal-combustion engine built around a rotary design.

The technology is owned and licensed in North America by Regi Tech, Richmond, British Columbia, Canada ( Its makers claim a RandCam engine would have two to three times the power and weigh half as much as a Wankel engine of the same size.

The engine is comprised of a disc-shaped rotor and driveshaft which turn the housing, or stator, which remains stationary. Up to 12 vanes mounted parallel to the shaft slide up and down along the outside of the rotor as they follow a track along the inside of the stator housing. Combustion chambers form between the rotor, stator walls, and vanes, and their volumes change as the vanes move during rotation. Although the design could use only two vanes, the current version has 12, which generate 24 combustion events (intake, compression, ignition, exhaust) per rotation. This lets the engine generate 1 hp/0.75 lb, as compared to a conventional internal-combustion engine's 1 hp/6 to 7 lb. The engine has a compression ratio of 20:1, which lets it burn a variety of fuels, including diesel. It also uses 13 moving parts rather than 40 for conventional piston engines. That's because the rotor and vanes replace timing gears, connecting rods, pistons, cylinders, and valves. This should improve reliability and cut manufacturing costs. The engine also generates lower vibrations because all the components are spinning in the same direction. There are no pistons or valves making thousands of abrupt changes per minute. The combustion chambers are also balanced around the rotor, plus the rotor acts as a flywheel to smooth out power imbalances and eliminate destructive harmonics. The makers admit, however, that tolerances are crucial to efficient operation of the engine. Based on its high-power density, low weight, reduced vibration, and multifuel capability, a 42-hp version will likely be installed soon on a military UAV.

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