Late to the party, but I really like this engine design.
In conventional engines the pistons have 4 distinct tasks: draw in fresh air, compress it, convey the pressure of the combustion phase to power on the crankshaft and push out the exhaust gas.
But this engine has no pistons. Instead it has a pair of single-toothed
gear pumps and a rotating valve to transfer the compressed air to the combustion side at precisely the right time.
The beauty of the design is that it is very efficient. The compression is done by the notch on the first pair; it pushes straight in, without sideway motion or forces.
Likewise the combustion pushes against the notch on the second pair, again driving it round in the direction of movement.
It is pure torque to compression and pressure to torque.
The difference with ordinary gear pumps is that one of the 'gears' does not have teeth at all' instead it just has a gap. Unlike in a gear pump that 'gear' is housed tightly and no air passes around that gear.
All air moves with the notch on the other gear until it meets the part where both wheels touch and it can go no further, getting compressed until the gap in the rotating valve allows it to the combustion side just in time.
There the notch has just lifted out of the gap, opening a steadily increasing combustion chamber. The gap in the rotating valve moves away, the spark plug ignites the gas, the pressure rises and pushes the notch forward - until it passes the exhaust port just before dipping in the hole of the other gear again.
On its next pass it will push the exhaust gas out of the chamber while being pushed forward itself by the next combustion cycle.
So how can this engine be so light, yet so powerful?
- It is quite simple. It only has rotating parts on 2 counterrotating axles, nothing else. No camshaft, no crankshaft, no pistons swinging up and down.
- It is nicely balanced. Because it only rotates it should not vibrate much.
- It can rev like crazy. 25K RPM... Plus every single rotation is a combustion cycle, much like a 2 stroke engine - which this isn't, for the lack of strokes.
- There should be very little friction. No sliding motion, no metal parts swinging back and forth, no pushing at an angle on connecting rods.
- Heat management should be simple as there would be no need to cool the part of the chamber where the combustion takes place. The hotter the better, I guess. The gear wheel should probably remain relatively cool to prevent premature combustion.
Sealing the valve wheels to prevent gas moving past the notch, between the gears or past the bearings is important. Yet as it only turns it can be made to fit very tightly, especially when metal with al low thermal expansion coefficient is used or when (if all else fails) care is taken to heat the gear chamber to match the temperature in the notch so they expand likewise.
This is a deceivingly simple yet very clever engine. I wonder what will come of it. This could be part of a tiny yet effective range extender for EVs...!