Supposedly this engine has superior fuel economy and emissions characteristics. As far as I can tell, it is a two stroke engine. Instead of using crankcase scavenging, it uses the lower portion of the cylinder to pump the air necessary for charging the combustion chamber.

It is also claimed that the "Balanced Precision Reverse Cam Effect Roller Crankshaft" did good things too, although from the animation it looks to me that it just results in the piston spending more time at TDC and BDC, and I'm not sure the advantage of that. It apparently is also known as a "Scotch Yoke." The engine is also supposedly "self supercharging."

It is also claimed that the exhaust gas temperature is 190 to 240 deg F, the compression ratio varies from 8:1 to 20:1, and that the air/fuel ratio is 30:1 to 50:1.

I have spent some time looking at the animation, and while I would believe the engine would run, I just don't see how it is "self supercharging", I don't see the advantage of the "Scotch Yoke", and I don't quite understand how it would operate with a 30:1 to 50:1 fuel/air ratio.

Looks basically like a 2-stroke, but with the fuel injected in the transfer ports. Not sure why this is environmentally friendly, since 2-strokes main problem is allowing uncombusted fuel out the exhaust. Admittedly CFD has improved this in recent years, and if fuel is injected after scavenging situation is better.

Self supercharging is a misnomer - they are really self scavenging engines. Nice bit of design, but I'm not sure why it should have higher sfc than most engines. A 2-stroke diesel, now theres an engine to hanker after - especially if it is matched to a turbo for scavenging.

This unit will still have the old problem of allowing the last bit of exhaust pressure to escape untapped. At first I wondered if the Bourke cycle was a piston brayton cycle. This would be very efficient, since the expansion could be greater than compression. Cool exhaust would also result. I think these units just use the coolant to keep the whole combustion cycle at a controlled temperature.

The scotch yoke may wear prematurely too. I prefer the epicycloidal mechanism (rotary engines are one example), although this would require an X-4 config. There have been some nice demos of this, but I'm not aware of any actual engines.

I'm interested to hear a thermodynamic explanation of why this engine is meant to be so good though!

If you could get ignition at an air/fuel ratio of 50:1 I could understand why the exhaust gas temperature would be quite low. In addition, the combustion temperature at an A/F ratio of 50:1 would be quite low, which would explain low nitric oxide production, and the PM's might be low by virtue of the excess oxygen present in such a lean condition. But it looks to me that the power density of such an engine would be absymal.

Here is an abridged version that took considerably less time, and is probably more concise, precise and less provocative, so maybe the timeout was a good thing after all

For my previous post, I was missing a lot about this engine, as I must confess I never read all the posts, and as the links seemed to go to sites with technically poor content, I did not spend much time on them.

I have since attempted to rectify this, but after to much research when the quality of the source information is taken into account, I must admit I am still missing a lot, including nearly half a day of my time.

On all the links I visited, I could not make an animation or video work, so I still have not seen the cycle and I am trying to imagine it from the very few drawings an photos of parts

There are minor differences in piston acceleration rates, and this engine has a small advantage in the piston having pure harmonic motion, and certainly no side loading is an advantage, however the pistons on each side travelling the same direction, as Greg points out will be a balancing disaster.

My comments in my previous post are based on petrol and spark ignition as the fuel.

I see no difference between the way fuel would burn in this engine compared to any other 2 or 4 stroke piston engine.

I see no supercharging as the air below the piston is squeezed into the same volume above the piston.

Lean mixture will result in detonation and destroy the piston, unless it is built to diesel standards that withstand detonation.

The only valving I see in the sketches and drawings are piston port type like any modern 2 stroke. As there is no apparent scavenging or supercharging, I don't see how it runs at all, if the cylinder with residual exhaust gas is over atmospheric pressure.

In my previous post I was taking power density rather than thermodynamic efficiency into account, and my views would soften considerably if only TE was being considered, however I expect that all engines must be a compromise between inertia losses from reciprocating weight, thermal efficiency via expansion ratio.

To answer SBBlue's comments directly:-

To have peak pressure by TDC, you must ignite the fuel considerably before TDC unless you have instantaneous combustion. This time to burn generates some pressure well before TDC, and considerable pressure a little before TDC, all of which resists rotation of the engine.

Even if you have detonation, you still need some time for the pressure to build up before TDC so it will be maximised by TDC.

I agree, using prolonged combustion to maintain peak pressure for a longer portion of the power stroke will give higher power density, but very poor conversion of the heat to mechanical pressure, all other things being equal.

Re NOx emissions. I have been taught that lean mixture, high compression and to much advance all lead to NOx emissions. The high compression and/or excessive advance generates more peak pressure, and therefore more heat. In the presence of free oxygen (from lean mixture) and nitrogen, NOx is then formed. I have never seen evidence to the contrary on this point.

MORE NEWS