A harmonically reciprocating piston rotary engine having a crankshaft, a piston rotatably supported on a crankpin of the crankshaft, and a rotating cylinder wherein the piston reciprocates sealing one side of a combustion chamber.
For a complete reciprocation of the piston inside the cylinder they are required two rotations of the crankshaft.
Without external balance shafts, the balancing of the inertia force, moment and torque is perfect (even for the single cylinder).
A synchronizing gearing keeps the cylinder rotating at the same direction with the crankshaft and at half angular speed than the crankshaft; the high pressure gas in the combustion chamber does not load the synchronizing gearing.
The motion the piston performs along its cylinder, and the motion the center of the crankpin performs along the same cylinder, are substantially the same.
Not only the power passes directly to the load and the synchronizing gearing remains unloaded but, additionally, the cylinder liner remains rid of thrust loads.
The PatRon is not limited to single acting pistons; it can utilize double acting pistons, too:
or even "multi-acting" (yet single piece) pistons:
The stroke S of the piston along the cylinder equals to four times the distance between the (fixed) rotation axis of the crankshaft and the (fixed) rotation axis of the cylinder.
The relation between the displacement D of the piston along its cylinder and the rotation angle f of the crankshaft is like:
which is a pure sinusoidal (or harmonic) motion.
In these two drawings (above and below), at the intersection of the three axial lines (dash dot lines) is where the rotation axis of the crankshaft and the rotation axis of the cylinder intersect the plane of the drawings.
The "casing" whereon the cylinder and the crankshaft are rotatably mounted is "single sided" in the following drawing (wherein at (a) it is shown the casing and the cylinder, while at (c) it is shown the casing and the crankshaft):
With two wings secured on the two cylinder heads to form a propeller:
it results a propulsion unit for light airplanes, ultralights etc.
The driving of the propeller by the cylinder (and not by the crankshaft) causes the loading of the synchronizing gearing (in the specific case the synchronizing gearing acts as a reduction gearing, too):
The single sided casing is not obligatory; in the following drawing a double sided casing surrounds completely the rotating cylinder (safety):
Here is a "sleeve valve" version:
that fits with long piston stroke and "through" (or uniflow) scavenging:
Click here or here for two animations of the above PatRon Sleeve Valve engine.
Or click here or here for the above animations in slow-motion.
The PatRon is for four-stroke engines, too (shown with PatRoVa rotary valves in the following drawing, which also shows how a single piece crankshaft can serve several cylinders):
With the PatRon:
* the power passes directly to the load,
* the synchronizing gearing remains unloaded by the high gas pressures during the compression - combustion - expansion,
* the two halves of the "immovable" casing (one per side of the spinning cylinder) are easily coupled / bridged forming a space wherein the cylinder spins safely,
* only one crankshaft is required (and only a set of balance webs secured on the crankshaft for the complete balancing of the engine),
* there are no high speed bearings loaded by heavy inertia loads,
* in case of air-cooling the rotation of the cylinder simplifies things (the cylinder is also the fan),
* if desired, the power can be delivered by the rotating cylinder (which spins at half crankshaft speed).
In the following animation there are two rotation axes normal to the plane of the drawing:
a first rotation axis at the intersection of the vertical dash-dot line with the top horizontal dash-dot line (about the first rotation axis the crankshaft spins and the piston orbits; the piston perfoms one more motion: it spins about the center of the crankpin);
and a second rotation axis at the intersection of the vertical dash-dot line with the bottom horizontal dash-dot line (about the second rotation axis the cylinder spins).
Here is a PatRon engine for small airplanes: it is, among others, a 2-stroke direct-injection (preferably Diesel) perfectly-balanced with unconventional scavenging.
The animation shows, among others, the casing whereon the spinning cylinder and the spinning crankshaft are rotatably mounted:
Here are shown the parts of the above assembly:
The bore is 120mm,
the piston stroke is 60mm (the bore to stroke ratio is only a little higher than the 1.91:1 used in the Ducati Panigale 1299 wherein the bore is 116mm and the stroke is 60.8mm),
the capacity is 1357cc.
The maximum dimension of the rotating cylinder is only 305mm (1ft).
With some 15% longer piston dwell at the TDC (harmonic motion of the piston relative to the cylinder, which means additional time for the efficient combustion of the fuel), the peak power of a direct-injection Diesel like the above can be provided at some 5,000rpm of the cylinder (i.e. 10,000rpm of the crankshaft) and is comparable (if not more) than the peak power of the Panigale 1299 (205bhp).
The scavengining is different:
At some angle of the cylinder the piston opens the "leading" port and the pressure of the gas in the cylinder drops sharply.
Several (like 10 or 15) degrees later the piston opens the trailing port, too; the exhaust happens through both ports; gradually the leading port becomes the intake port with the trailing port being the exhaust port.
The motion of the cylinder in the ambient air pushes air to enter from the leading port to scavenge the cylinder and then to exit from the trailing port.
After the BDC the pistons moves "upwards"; initially it closes the trailing port; the air entering the cylinder from the leading port continues to enter (due to inertia) until the piston closes the
leading port, too.
The gas in the cylinder is compressed. Near the TDC diesel fuel is injected into the bowl at the center of the crown of the piston.
After the TDC it follows the expansion.
After the middle stroke the piston opens the leading port (it serves as exhaust port and as intake port) and so on.
I.e. it uses neither crankcase scavenging, nor some external scavenge pump.
The combustion chamber is like a long room (say, a corridor) having a big window towards the north and another big window towards the south.
Outside the room it blows a strong wind coming from the north (this is what the rotation of the cylinder causes).
At the end of the expansion (a little after the middle-stroke) the north window opens. The pressure in the room is high.
The high pressure in the room pushes a big part of the "air" to exit from the north window and the pressure to drop sharply.
A little later the south window opens allowing gas to exit from that window too.
Due to the north wind, the flow from the north window gradually weakens, stops and reverses its direction, while the flow from the south window strengthens.
With both windows wide open (BDC), the strong north wind enters from the north window, scavenges the room (and cools down the walls, the ceiling and the floor of the room from within) and exits from the south window.
Later the south window closes, with the north window still open.
The wind continues to enter into the room from the north window (due to inertia / ram effect) overfilling the room with air (a kind of asymmetrical port timing: the exhaust closes before the transfer).
Finally the north window of the room closes trapping the air entered,
and the compression starts.
At 5,000rpm of the cylinder (10,000rpm of the crankshaft) the speed of the leading port of the engine of the above animation is about 200Km/h (125mph) provided the engine is not moving in the air. If the cylinder is moving in the air, the leading port "sees" the air coming at an even higher speed.
The following animation shows the cooperation of the cylinder, of the crankshaft and of the piston :
The following links / animations are for a slighly more compact version of the above design.
For the same bore (120mm) and piston stroke (60mm) the maximum dimesnion of the rotating cylinder is 280mm (11 inches).