Great New IC Engine Idea

[Philip]

The following link is to an article that was featured on the front page of the January edition of Popular Mechanics South Africa.

http://69.143.55.21/scuderi%20engine-za.pdf

I think that it looks like a very promising technology. I've been following it for some time. I'd like to know what everyone thinks. Please don't give me reasons it's not going to work without taking a chance to understand how it works.

[jutz]

Okay, they talk about other new engine designs (such as the Wankel) requiring "exotic components and unique materials" as a negative and eight paragraphs later mention that modern construction techniques and materials, high-temperature lubricants and special coolants should be able to overcome the problems already identified by the test laboratory. I always get doubtful when I find that kind of doubletalk.

Personally, I doubt that the improvement in efficiency will exceed the loss of efficiency due to the extra piston and cylinder. Also, it will be physically larger than current 4-stroke engines of similar power and have significantly more moving parts (more expense, more failure potential).

I also think the significant increase in burn rate they're attempting to achieve will increase the tendency for detonation and require special fuels.

[Orrin]

It bears a strong resemblance to the Reid oilfield engine. The Reid employed a separate charging cylinder, much like this one has.

I cannot see why there'd be any increase in efficiency by using a separate compressing chamber. If anything, there would be losses because there's bound to be a pressure drop across the transfer passage.

[img]/ubb/images/graemlins/cool.gif"%20alt="[/img]Orrin

[Philip]

I think that the increase in efficiency would come from the fact that in this design when you get your spark the power piston is offset from the crankshaft. If I'm not mistaken you'd have a huge decrease in friction because of this.

Why do you think there would be a pressure drop across the transfer passage? I think that the way they've got it set up it would just act like a queue. If you timed it correctly I can't see how you'd lose pressure. However, that's what I personally would worry about the most. The timing would be critical in my view.

Good post. I'll have to check out the Reid oilfield engine you speak of.

[Philip]

I don't like the doubletalk either. Does anyone know the exact reason the Wankel didn't catch on anyways? I've got to think that what they're talking about with the problems identified by the test laboratory is that the power/exhaust piston would fire every other revolution and thus get pretty hot. That's the biggest problem I can gather from this. I've heard that Saabs use ceramic pistons. Does anyone know how that's been working out for them?

I'm not convinced that it would be significantly larger. Emphasis on significantly. They're adding an extra piston and cylinder, but because the extra piston and cylinder give you a power stroke every revolution (as opposed to every other) you'd still have the same number of cylinders. For every two cylinders you'd have 2 power strokes every 2 revolutions. It might be a little bit bigger because of the transfer passage though.

I think the increased burn rate would be inherent in their design because you'd have gas coming out of that passage that would be turbulant as all hell.

Can you elaborate on the detonation thing? Isn't that the whole idea? [img]/ubb/images/graemlins/smile.gif"%20alt="[/img]

I've contacted the company that's trying to push this thing and they sent me a very nice promotional video. I'll post it as soon as I can figure out how to encode it.

[Doug_C]

I was thinking along that line myself. The one factor I think they do not mention is whether there is a difference in bore size. It could get a pressure intensification if the power side transfers to a smaller piston? That could be counterbalanced with the crank?

Some of this theory of mine, is what makes striling engines move with such low differentials in heat expanding over differential piston surface companions.

Time will tell. Since it has only been modeled in computer space, it is those things in the real world that may be unforeseen. Although it appears that they have covered most of their bases.

The thought of the flash of fuel being so short would seem to indicate a higher volatility of the mixture required. The standard 14:1 mixture these days does not seem realistic for the short crank angle of 10 degrees. My concern there would be that it would need twice the RPM to put out the same amount of torque. Longer crank angle duration=torque?

Then again, if as already mentioned in timing wherein the power cylinder is timed passed TDC, while the compression cylinder is at or slightly before TDC and not capable of using all the forces created during detonation pushing down on the piston in line with the crank throw for a short duration either side of TDC. That in itself will allow the power piston to assist the power stroke earlier in the cycle via the crossover passage.

Hmmmm, more to contemplate on this one.....



DC

[jutz]

Ummm... this detonation thing. Try <a href="http://www.motorcycle.com/mo/mcrob/rt-f ... l2.html</a>. If that's too technical try a web search under "detonation" and you'll find all sorts of links to stuff of varying levels of detail (and accuracy) about detonation. The short explanation is detonation is an explosion of the charge in an engine and, despite what you'll frequently read in magazines like Popular Mechanics, it is NOT what you want. It will destroy the engine. What you do want is a rapid but controlled burn of the charge.

There are lots of reasons the Wankel hasn't really caught on, not least of which is that it's competing with an engine which has 100 years more development time. It also doesn't help that the trochoid chamber is much harder to make than a cylinder so it doesn't get as much casual development assistance from tinkerers.

The Wankel really only has two advantages over piston engines: compactness and simplicity. Neither of these means a thing to the vast majority of automobile owners who are put off by it's two major disadvantages: cost and inefficiency. Both of these disadvantages can probably be dealt with through development but, as I've already mentioned, the Wankel's main competition has a 100 year head start.

As for the very nice promotional video... Very nice promotional videos are produced by salesmen. Good engines are rarely produced by salesmen. I'd much rather see a functioning prototype.

[Doug_C]

Detonation is usually a pretty loose term for ignition from spark.

Pre-detonation which is a product of the compressed mixture going off before the spark has initiated the burn. Pinging etc can be caused by poor fuel mixture, poor timing and a hot running head? High compression engines do not help much with low grade fuels. When it diesel detonates it is pinging while the piston is still going up. The charge is fighting the pistons momentum. Definitely not good on any part of the reciprocating assemblies even though the piston takes the brunt of it.

DC

[Philip]

As for the very nice promotional video... Very nice promotional videos are produced by salesmen. Good engines are rarely produced by salesmen. I'd much rather see a functioning prototype.

I couldn't agree more. Salesman are a necessary evil;)

[CudaMike]

Isn't the intake valve on cylinder no. 2 going to get fried since it is open when combustion starts? The intake valve is on its seat during combustion in a conventional 4-stroke. The exhaust valve comes off of the seat after the combustion is essentially complete, and when it closes the heat in the valve head is dissipated into the head. Of course, top fuel dragster and funny car engines are the exception, with the nitro still burning even coming out the headers.
I'm skeptical like the rest of you. I'm going to have to study this thing for a while.

[Philip]

I think there's no doubt that at the very least that valve would have to be made of a more durable material than the valves used in normal Otto cycle engines.

Based upon your comments I suppose the question is could the valve technology employed by top fuel dragsters and the like, or simply a titanium valve solve this problem?

I'd sure like to get my hands on that computer modeling analysis.

[Philip]

I'd like to thank everyone for their comments. I definitely came to the right place to have this discussion. You all seem very knowledgeable - much more so than myself.

Anyways, in case anyone is interested - I dug up some more information on the inventor. I have a friend that works in the refrigeration industry. He's pretty sure that this is the same guy that invented the oil-less compressors for refrigerant recovery machines that completely took over the market about 10 years ago and still dominate today. He did it by offsetting the compression piston - reducing the friction enough to completely eliminate the need to use oil. Perhaps that lead him to this.