The Ecomotors OPOC engine has money 6

[turbomotor]

More than a year ago (12 Feb 09), Painterman(Mechanical) started a thread 71-237389 to address the question of opposed piston engines. The thread was popular, and some of the discussion diverged to the subject of Prof. Ingr. Dr. Peter Hofbauer's OPOC engine. (Hofbauer is the ex VW Powertrain Development boss who conceived, prototyped, and continues to develop the OPOC engine concept.)

At that time, I somewhat dismissed the OPOC engine because I understood that DARPA had discontinued their financial support of the concept development.

Well, I may have made a very big mistake in dismissing the concept. Ecomotors (the company started to exploit the OPOC concept) has recently secured additional funding for further development. We may yet see a production version of this concept.

My question to you astute and discerning gentlemen (and ladies): Do you think this thing will actually work well (in the real world of prime movers)?

Dick

http://www.ecomotors.com/news/

 

[TrackRat]

It will be interesting to see if this project goes any where.

 

[TDIMeister]

In addition to having worked in the same company as Prof. Hofbauer before founding EcoMotors, I received an M.Sc in the same University in Germany of which he is an alumnus.

I've had a chance to take a closer look at the working of the OPOC engine, so I can make some revisions to my critique that was made in the abovementioned thread.

As stated before, a very slight secondary out of balance exists because the L/R ratio and hence motion profiles are different between in the outer set of pistons compared to the inner. Also, depending on the masses and positions of the CoG of the two pairs of rods, their forces don't cancel-out completely.

As for the need for a scavenging blower, this could be eliminated by using the outer volume of the outer set of pistons as scavenge compressors. Further boosting could be achieved by exhaust gas turbocharging.

I think this engine will prove useful for unmanned drone aircraft and the engine packs in range-extender hybrids.

 

[tbuelna]

Dick,

You, of all people, should understand the issues with this particular engine configuration. Remember the issues with injector nozzle location and spray geometry on the TRC engine? And the persistent compression ring scuffing due to lack of liner surface oil film near TDC, caused by the limited stroke overlap between the oil control and compression rings?

Personally, I don't see the OPOC engine making much headway in the mainstream recip engine market. It's only real benefit is good power-to-weight. But there are other recip piston designs that can potentially do better, without the OPOC's limitations.

The only thing about the OPOC engine that really impresses me is Hofbauer's ability to keep raising money for it.

Here's an interesting proposal based on the OPOC engine:

http://ila2010.eads.com/data/8b9e95...dc8cc63dbc3ccafc98b9ea177c2dfddc57ddaaa93.pdf

Hope you're doing well.
Terry

 

[TDIMeister]

The forced side position of the injectors is far from optimal based on current practise for compression ignition engines. However, an engine that could run highly-premixed mixtures (e.g. HCCI, PCCI, etc.) over a wider operating range could render the point moot.

I agree that lubrication is a problem, especially for outboard pistons and the associated gudgeon pins and rod small-end eyes that cannot have the benefit of an oil spray the way the inboard pistons can.

 

[YvesLLewelyn]

Let's be honest about OPOC's engine - it is hopelessly bad.
The claims are wildly exaggerated or just plain ridiculous.
The real point of interest with this engine is how somebody as apparently impeccably qualified as Hofbauer could come up with something as bad as this. If it wasn't for Hofbauer's credentials nobody would look twice at this engine. Do people like Hofbauer get to the top of the academic and commercial automotive world by political manoeuvering alone?
And somebody as clever as Bill Gates has invested in it? It is a very strange world.

 

[Satanicusmaximus]

Given the huge difference between thier engines power density and the comparison engines on thier site one can only assume that the comparison engines are infact 4-stroke engines. I bet an ordinary direct injected 2-stroke engine with the same displacement as the OPEC engine would perform equally as well.

 

[PJGD]

Remember the issues with injector nozzle location and spray geometry on the TRC engine? And the persistent compression ring scuffing due to lack of liner surface oil film near TDC, caused by the limited stroke overlap between the oil control and compression rings?

Terry: Don't lose sight of the fact that the role of an engineer is to be ingenious. His job is to solve vexing problems, and you have identified just such a problem. Interestingly, both Achates Power in US2008314688 and EcoMotors in US2010050978 have attempted to address either your noted problem or something close to it. In other words, where there is money and/or a will, there is a way so I suspect that the problem will be resolved eventually.



The forced side position of the injectors is far from optimal based on current practise for compression ignition engines.

TDIMeister: I agree with your statement as it stands, however there has been continuous development of on-axis combustion systems since Saurer patented the concept with toroidal chamber-in-piston in the mid 1930's and it demonstrably works well. There has been far less development of side injection combustion systems. Nevertheless, I would be interested in your views on what you perceive to be the problems or shortcomings of side injection systems?



Let's be honest about OPOC's engine - it is hopelessly bad.
If it wasn't for Hofbauer's credentials nobody would look twice at this engine.

YvesLlewelyn: Could we please have some rationality in our postings? Your statements need backing up with logical explanations of what is so bad and hopeless and why. For example, there must be some detail of the engine that you believe to be hopeless but you don't say what it is. It can't be the basic OPOC concept since Hofbauer's engine was anticipated by Mercedes-Benz in DE19503444 from 1995, not to mention a Herr Fischer in DE4135386 of 1991, so others certainly have looked twice at it.

I have no direct connection with any of these engines; if I had, I would probably attempt to refute Satanicusmaximus's assertion. However your considered responses would be appreciated!

PJGD

 

[tbuelna]

PJGD,

"In other words, where there is money and/or a will, there is a way so I suspect that the problem will be resolved eventually."

I don't disagree with that statement. The development history of the Wankle rotary engine is proof of that. Like most of you though, I'm an engineer and gearhead. So there's nothing I like more than watching a mechanical gizmo that makes noise and goes round-and-round. But I've also worked on many engine development programs in my career, including a couple of OP diesels. So I have intimate knowledge of their shortcomings.

While I wish Prof. Hofbauer and Bill Gates well with their endeavor, in the end I'm sure it will come to naught. Getting an engine into production and generating a profit costs hundreds of millions of dollars, which is much more than the $23 million Mr. Gates has invested in the OPOC project.

For any consumer product, such as an IC engine, to successfully displace an existing product, it must be better in every way, including cost, performance, reliability, marketability, etc. There's a reason the recip piston, 4-stroke, overhead poppet valve IC engine is universally used for automobiles. It's because it gives the best compromise of all of the market demands.

Bill Gates has just poured his $23 million down a rat-hole. But he's not stupid, so maybe it's just a tax write-off.

Here's a great book on the subject of OP engines.

http://books.sae.org/book-r-378

The most interesting fact about OP engines is that the only profitable, and thus successful, OP engine is the Fairbanks-Morse 38D. It has been in production for over 70 years.

Regards,
Terry

 

[PJGD]

Terry,

Yes, you are preaching to the converted with respect to development costs and probability of commercial success. However, there are several OP engines in development at present, each different in various ways and I am hoping that some technical papers will eventually come out that will discuss the development challenges that were faced and perhaps overcome.

Eventually, if the market needs an engine having the attributes that OP engines bring, then someone will be able to use those resources plus the outstanding Pirault/Martin book to design a successful example.

While I agree that the Fairbanks-Morse 38D has to be considered a commercial success, I would argue that several other OP engines were too in their day. The Doxford OP engines were in production across 70 years also. The Trojan and the Rootes TS3 engines were probably commercial successes while they were being made also.

PJGD

 

[TDIMeister]

Don't forget the various Junkers Jumo series.

 

[PJGD]

It's OK, we had not forgotten the Jumo (the Pirault/Flint book has an excellent review of these engines). I'm just not convinced that they made enough of them to be classed as a commercial success.

Had the war not got in the way, I think that engine would have been a great success particularly on transatlantic flights. But as it was, the accelerated development of the jet engine would have done for the Jumo what it did for the Nomad concept. The Jumo would have found a home in Coastal Command aircraft or other Cold War military aircraft but it would not have had much use after the mid 1950's, I think.

PJGD

 

[ArthurP4140]

This "Kneeslider" site link is interesting. The NSU engine shown appears to be not just similar but virtually identical to the OPOC engine. How do patent laws allow this?

http://thekneeslider.com/archives/2...roke-engines-opposed-piston-opposed-cylinder/

 

[PJGD]

Arthur:
The NSU engine is in the old motorcycle that is pictured and it is a parallel twin layout with common combustion chambers, I believe. The sectioned engine immediately above the bike is still the EcoMotors OPOC.

PJGD

 

[OldJagMk5]

PJGD – The engine in the old NSU motorcycle is not a “split-single/twingle”. I don’t think NSU ever made a “twingle”. If you look at an enlarged picture of the old ‘bike you will see that the two tall black finned objects under the petrol tank are the cylinders and have no common combustion chamber. Evidence (such as the odd position of the exhaust) would suggest that the engine is what the magazine article says it is – a prototype opposed piston engine.
The sectioned engine picture is the OPOC engine. It was used in the article to illustrate the layout of the NSU engine. The OPOC engine is essentially a flat or horizontally opposed version of the parallel twin NSU engine.
VW absorbed NSU – Hofbauer worked for VW - it seems quite possible that Hofbauer/OPOC were well aware of the NSU engine and copied it although they don’t appear to acknowledge this.
It is also notable that NSU apparently didn’t notice any miraculous improvements in power and fuel economy as OPOC do with their engine of the same layout.
The engineer who worked on the NSU engine (I don’t know if he invented or originated the idea) was Otto Reitz. He went on to design a long series of “twingles” for Triumph/TWN. The implication would seem to be that he got the same asymmetric timing effects etc. as the opposed piston NSU engine in a much simpler way with the “twingle” arrangement.