If this is really practical, the applications for light aircraft should be huge.

What is power to weight ratio of other ICEs? 20:1 is a nice ratio but i would like something in which to compare.

Er, even 20 HP/lb does.

The state of the art in auto engines is about 100 HP/liter for high performance models (about 1.6 HP per cubic inch).  I can't tell you what the typical power/weight is for cars, but for opposed-piston light aircraft engines it is about 0.5 HP per pound.

Looks much like the Sarich Orbital engine:
http://www.ipaustralia.gov.au/patents/ex_orbit.shtml

This is what happened to it:
http://en.wikipedia.org/wiki/Orbital_engine

"...that promises high power output with a very high power to weight ratio (20:1)."
Sorry but as long as power and weight are not expressed in the same units, such a sentence is pure nonsense. I would certainly never trust an inventor who is not even able to use proper terms to describe his "discovery".

Given that it is an American inventor I would hazard a guess that they are saying 20hp to 1lb, but that is only specualtion since it isn't explicitly defined.

I believe the LS1 from GM weighs ~400-450lbs and developed 400hp in Z06 form that would give 1hp per lb but that is with emissions equipment (catalytic converters & mufflers), emissions requirements and driven accessories. Until they have this engine running in an EPA lab to ascertain compliance with automotive emissions standards the power it produces can't be compared.

For example: A drag car from Puerto Rico, known as Sakura, was running mid 7 second 1/4 mile times using a 2.6L 4 cylinder turbocharged engine developing somewhere around 1000hp (the motor used with turbocharger weighed around 350lbs) but don't expect that engine to meet emissions standards for noise or air.

Well, if you read the article, you would see that the claim was 150Lbs and 3000hp.

20hp : 1Lbs

Modern high output street legal engines Are between 1:1 HP:Lbs and 1.5. (Some bike engines offer 2:1 but not for very long :)

Someone earlier mentioned HP/Liter, but that is a measurment not useful for anything but marketing.
It bears no relivance to HP:Weight, nor reliability, nor thermal efficiency or emissions. It is a moron's litmus test.

This engine is potentially exciting, but I agree with previous posts, I want to see it run on a fuel, and I have doubts about 150Lbs worth of material handeling the stresses from 3000hp, or even half of that.

I agree Tom,

With this much heat thermal cooling is a big problem.
I'm not sure how they are going to achieve good combustion in only 90 degrees CA. This is too short even with hydrogen. The exhaust heat losses will be very high and reduce the thermal efficney. I'm not sure how they are also achieving a high compression ratio with this configuration.

The engine has high surface area for the outer housing this will disapate much of the heat and lower the thermal efficiency. The cooling the center rotor will be a big problem.

You also have a strange split line running down the center of the combustion chamber that separates the two different rotor groups of four. This split line will be prone to combustion gas penetration, especially at very high compression ratios.

How does this keep the combustion rotation in the desired direction? It looks like it would just produce center pressure that would go both forward and backward.

I think that they use some elaborate gearing system, but this will add friction and be prone to wear. This will add to the reduction of the brake thermal efficiency.

You might somehow get high power density, but you won't be able to maintain it for very long due to the thermal loading and you certainly won't get very good fuel efficiency from high surface heat and exhaust losses. This would be something that the military might try, but I can't see what it will do to help reduce our oil and fuel consumption.

Hmmm, power to weight ratio is 20hp/lb,eh? This proves that the inventor of this thing is an idiot when it comes to material science. Power is force times distance. Aluminum, Titanium and Steel can withstand certain amount of stress before they will break. The best heat engine (Diesel) is around 50% thermal efficient. This means that a lot of heat will need to be ejected from the engine before it will melt. A race-car engine is at the forefront of power-to-weight ratio, and at no more than 3hp/lb ratio, the limiting factor here is metallurgy, as the material cannot handle any more heat nor stress. A race car engine must be rebuilt after every race. A Wankel rotary engine is even simpler than the toroidal engine and it has no reciprocating parts, either, and a good Wankel engine has about 1hp/lb to 2hp/lb, no more.

This design does have better thermal properties than the Wankel; the ratio of surface to volume is much lower, and there appears to be no period where the intake and exhaust are interconnected.  The big issue appears to be the mechanical arrangements for moving the vanes.

This may have more potential as a topping cycle for gas turbines than as a stand-alone engine.  In a gas turbine, combustion occurs at constant pressure and the gases expand, increasing entropy.  Now consider a gas turbine blowing through an engine like this, running at 1:1 compression ratio and a larger expansion ratio.  The fuel would burn in a closed chamber and the gases would increase in pressure, deriving work from the expansion before being released to run the turbine.  An adiabatic engine built with silicon carbide combustion-chamber surfaces could eliminate most need for cooling, too.

If a gas turbine could get an extra 3:1 pressure ratio in the expansion stage, it would improve the efficiency considerably.  It would also let the turbine idle with much lower fuel consumption, as the compressor would not be required to generate sufficient pressure to keep the engine operating.

This design has MUCH worse thermal efficienies vs a Wankel, Engineer-poet, at least as described: the "dwell" of 12-degrees means the effective engine surface area at it's "TDC" is probably doubled, and since that is the point of highest temp/pressure, it'd have roughly twice the energy loss from heat as a conventional engine.

That 12-degree also reduces the angular distance for getting a good expansion ratio. If they were able to reduce the "dwell" and increase the expansion ratio, though, perhaps the efficienies would come back up. However, the reason they probably won't be able to, if they manage to build one, is that they have a terrible arrangement for the flame kernal at the spark plug. It's at the cylinder wall!! They'd get terrible incomplete combustion without the dwell, I'd imagine. And it gets worse: the gap of the plug can't extend into the swept area at all(!!) - so the rings will be going over a gap, which is not possible with current ring technology... you'll get immediate wear and strain to the rings.

The other problem to the rings & sealing is that the "cylinder wall" halves are moving in relation to each other, meaning these would have to be sealed to each other, which would be a HUGE source of friction that isn't mentioned. In an ICE, piston/cylinder wall friction is about 70% of total friction, but in this engine it'd be under 50% because of the addition in the friction from one-half of the cylinder wall to the other!!

Several technical points of the article are in error, under "features":

1. There is no way a gasoline engine can reach 70:1... and it's not a diesel since I see spark plugs. People have worked on high-compression gas-detonation engines, but this design isn't suited for it with its sealing issues.

2. Open ports with no restriction is not a benefit (one-way airflow is, though). I've seen the data from Lotus's cam-less high-pressure hydraulic valvetrain, which can mimic any profile, even square-wave... open values with a square-wave, though, and they actually have worse airflow. I also believe (though it's not mentioned) that this would be a very low-rpm, low-mean-piston-speed engine, so to salvage air-flow with some fancy variable-length-runner intake system may be difficult, due to the extreme length of the runners required. Probably measured in feet, not inches.

3. Air/Oil cooled? Are you kidding me. Everyone has already pointed out extreme cooling a 3000hp 150lb engine would require... of course what we really want is a 300hp 50lb version, I guess, but either way cooling requirements are basically bhp over thermal efficieny, so you'd need a larger cooling system than a normal 300hp engine, not a smaller/non-existant one.

4. No thrust loading?? Ok, take a bucket of water, and swing it over your head on a rope... do you feel loading on your arm? These piston skirts will as well... its centrifugal. There should be much less than the load caused by the kinematics of a connecting rod, especially if this is a low-rpm engine, but it's not zero.

5. Pistons don't touch the cylinder walls? Please. See #4

6. No reciprocation? The momentum loss in a "stop and go" system described here is EXACTLY equal to the momentum loss in a reciprocating engine, so this is technically accurate, but of exactly ZERO benefit.

7. There 6th bullet point is actually somewhat correct, cheers!

8. They almost had a run, there! But no... while it's true all the strokes happen simultaneously, this is not a benefit... because there are a lot of off-axis forces because every-other piston is moving together, but adjacent pistons are moving with opposing motions, and extreme & opposing forces. Note that the "upper cylinder head" function is being performed by the bottom-half of the trailing piston!! so these forces will require extremely robust construction, perhaps heavier-duty than a convention ICE engine that has seperate power/intake/etc strokes.

However overall, not having looked at the patents yet, and seen the air-engine demo, won't write this off yet. Well, I'll write it off for fuel efficiency and clean-burning, but if the sealing, intake, and combustion issues can be overcome, which is certainly possible, it would be very compact for it's power output, if not for it's weight. That is useful in some applications - tanks, airplanes, etc.

And it is original, at least to a wankel/orbital... I haven't looked at the referenced patents from '69 though, but even if it's not completely original to those patents, at least those patents have long expired.

Good luck to them I guess. Most of the errors I pointed out are just on people writing articles about engines who aren't engine people, or haven't thought through their own inventions I guess.

-Kevin

Under the hood of almost all modern automobiles there sits a four-stroke internal combustion engine (ICE). Though the efficiency of the design has been improved upon significantly in the intervening years, the basic concept is the same today as that used by the first practical four-stroke engine built in the 1870s...But the automotive industry may soon be revolutionized by a new six-stroke design which adds a second power stroke, resulting in a much more efficient and less polluting alternative.
[...]
...After the exhaust cycles out of the chamber, rather than squirting more fuel and air into the chamber, his design injects ordinary water. Inside the extremely hot chamber, the water immediately turns to steam– expanding to 1600 times its volume– which forces the piston down for a second power stroke. Another exhaust cycle pushes the steam out of the chamber, and then the six-stroke cycle begins again.
The Six-Stroke Engine

Thanks, Kevin for a thorough analysis, and especially in explaining that the two cylinder halves are moving against each other. I kept thinking erroneously that some kind of transverse cut out at the center of the torus allows the pistons to transmit their force to the center shaft. Now, then, the issue is even more interesting:
1) For the kind of pressure involved in generating decent horsepower in a IC engine, a cylinder half will be pushed away from the other half with the greatest of force. Let's say 500-600 psi at the end of combustion point, then the cylinder halves are pushed away from each other with forces of thousands of pounds. Now, let's see what kind of seal and lubrication would be able to hold up against that kind of force in that kind of heat without breaking down and excessive wear? not to mention heavy construction need at the junction of the seal, causing high inertial mass that must be stopped and go continously, thus accelerating the wear on the gearing mechanism that allows such a weird motion to occur. In a standard piston Otto-cycle engine, the piston pin and crankshaft are also exposed to high force right at the point of combustion, but the difference is that the piston pin and crankshaft are protected from the extreme combustion heat so that the oil won't get degraded, and that they are generously lubricated by fresh oil forced in under high pressure.
2) Dwell time of 12 degrees for complete combustion? Pure fantasy. This much time and 3000-5000 degrees F of heat generated and tremendous amount of force necessary to restrain the piston movement until the dwell time is over means tremendous thermal stress and mechanical stress on all the involved parts, such that, if this design will ever work at all, it won't last very long. How long can one expose lubricant to extreme heat of 3000 degrees F?
If you think that Wankel engine is having problem with rotor seal and efficiency, don't look toward this new design for salvation.
GOOD LUCK, MYT engine and Raphial Morgado, you are gonna need a lot of it!!!