I’ve stumbled upon this new way of making combustion engines called Round Engine, or it’s more techy-sounding name Variable Geometry Toroidal (VGT).

At first I thought it’s some kind of rotary engine but it’s not. I will talk about how it’s different later.

VGT Technologies Inc likens their VGT engine to a pushing merry go round, while normal engines are paddling bicycles.

Key aspects of the VGT Engine

  • Circular piston housing where the piston goes in circles instead of a straight housing where the piston goes up and down.
  • Crankshaft and conrods are replaced by a main disc which connects to the driveshaft.
  • Pistons are connected directly to the main disc. In a normal engine this means it’s connected directly to the drive shaft. The shape of the piston is unique, and has to interface with the timing disc to complete the cylinder.
  • The timing disc functions as the top of the cylinder.
  • Round Engine has only one compression and exhaust chamber. Air intake and exhaust valves are shown on the diagram. Variable valve positioning can be achieved with a slot and some mechanism to move the slot cover to create moving valves.
  • Combustion occurs outside piston housing in a separate chamber. This means only one spark plug is required. On larger engines, a second combustion chamber can be added directly opposite (180 degrees) the first combustion chamber.

How does it work?

Basically air is compressed by the rotating piston using the timing disc surface as the top of the cylinder. The air is compressed between the piston and the timing disc.

After that, air is moved to the combustion chamber by the piston. The valve closes and compressed air is trapped in the combustion chamber. Fuel is injected, spark ignited and combustion occurs.

The combusted air pushes the piston forward until the piston travels past the exhaust valves. The gas is then exhausted through the exhaust valves once the piston moves past the exhaust valves.

Basically for each rotation of the drive shaft, two combustions will occur because the Round Engine has two pistons.

Differences between the rotary engine and the Round Engine.

The rotary (Wankel) engine is elliptical while the Round Engine is perfectly round. The two engines also use different torque arms. Because of the shape, a rotary engine’s torque arm continually varies similiar to a normal piston engine. But with the Round Engine, the torque arm follows a perfect circular path so the torque arm is always constant.

Other benefits of the Round Engine design include smoothenss because the circular motion generates virtually no vibrations. Limited amount of moving parts also increases engine life. The design is also modular, allowing multiple Round Engines to connect to the same drive shaft.

Before this blog post gets too long, you can check out more about the Round Engine at VGT Technologies Inc.