Opposed Piston Engine-3 cyl.

Status
Not open for further replies.
Interesting but I see some pretty big challenges:
Emissions - Fixed port 2 strokes do not do well with this
Weight - extra crankshaft and supporting block structure is heavy
Weight distribution - the extra weight is all high, no good for CG, so hard to adapt to cars
Packaging - It is a tall heavy engine - again maybe target use is SUVs and Trucks.
 
Interesting but then I remember whenn the media was pushing how great the Wankle would be. Yes I am a skeptic. The fuel injected out board engines for example are more complicated that the old carb engines but their performance and emissions are stellar in comparison. Good mpgs are always a plus . Over the past year with the driving I do I have been geting 21 to a bit over 23 mpg on my 2015 F150 . More Mpgs would always be better with a lower cost of operation [long term reliability] Lets hope it is a plus and pans out to benefit us all.
 
We can do a number of things to improve thermal efficiency. One is to increase the displacement of a cylinder by using fewer but larger cylinders. As this results in lower thermal loss to exposed surface area. This also serves to reduce piston ring swept area, reducing friction.

Low heat rejection engines can be built using coatings to reduce the transfer of combustion heat to surfaces. Or engines can be operated at very high temperatures, thereby reducing heat flow. (an opposed piston engine is the latter type) as the pistons operate at very high temperatures. It eliminates the cylinder head as a thermal path.

Also, like the modern and hyper efficient (41%) Prius engine, configure the engine to have a higher expansion ratio (more expansion than compression) . Done with intake valve timing AKA Atkinson cycle. In opposed piston designs some think it can be done by port and piston timing via geometry. Possibly including the use of different stroke lengths, different connecting rod lengths, differing piston positions, and so on.



This design may accomplish some of that inherently, however, I fail to see how the predicted huge gains are met. 45% thermal efficiency is, at the moment, an area of operation reserved for well refined diesel engines.
 
Last edited:
Eliminating the cylinder head and combustion chamber is eliminating a major area of thermal loss. Further, the heat that used to be lost instead goes to another piston.

Could be some real game changing stuff.
 
The most efficient engine at this point is the Wartsilla 31. Of course, with a bore of 11.8 inches, 16.7 inch stroke, nearly 1000 horsepower per cylinder, and max RPM under 1000, not practical for land transport. Really efficient though.

Rod
 
Opposed piston engines go back for more than 100 years, and were making 40%+ thermal efficiency long ago.
The English had successful OP engines for ship propulsion by the early 1920's, and some of those included waste heat recovery.
The Germans had the Junkers 204 OP diesel for commercial aircraft before WW2, and the 207 version was even turbocharged.
The Americans had the Fairbanks Morse 38 D 8+1/8 for submarine propulsion in WW2, and diesel electric locomotives postwar. That engine is still being constructed in Beloit, Wisconsin.
Then there is the Napier Deltic that is a 3-bank, 18-cylinder OP that was used for locomotives and Royal Navy MTB's. Lovely engine, sounds like a Detroit Diesel on Benzedrine.
I think Achates may be onto something. Cummins recently bought into their project to make a 4MW engine for power generation.
 
Originally Posted By: Danno

Weight distribution - the extra weight is all high, no good for CG, so hard to adapt to cars
Packaging - It is a tall heavy engine - again maybe target use is SUVs and Trucks.


Turn it on its side? Subaru does it.(kinda)
 
Originally Posted By: Miller88
For some reason the video wont' load, but if it is what I think it is, look up the commer TS3 ...


Yes, a rehash of the TS3, but using an extra crank instead of the rockers in the TS3. We didn't hear it running (I wonder why)... I reckon if you heard it running you'd be sold - the TS3 was the best sounding engine ever.
 
Originally Posted By: Silk
Yes, a rehash of the TS3, but using an extra crank instead of the rockers in the TS3. We didn't hear it running (I wonder why)... I reckon if you heard it running you'd be sold - the TS3 was the best sounding engine ever.
 
Back in the late '80s, I was doing drawings on jamming a couple of 186s together and opposed pistons...all ideas, no practicality.

If you start messing with crank timing and rod length/stroke, you can achieve a lot of different effectss, including having the pistons "chasing each other with variable volumes at either end...fun with geometry and physics.

Here's the inventor.

I like him
 
From what I can find, the older opposed piston designs are not as efficient as modern diesels. And, since we've been using the design from the late 1930's, I suspect the older designs are very refined and mature.

I have to wonder how the computational fluid dynamics aspect plays into greater efficiency.

On another note, a two stoke engine is entirely devoid of the friction creating, non power producing stroke of any typical 4 stroke, the exhaust-intake stroke. As in a two stroke, each time the piston goes down, it's producing power.
 
Originally Posted By: JamesBond
Originally Posted By: Danno

Weight distribution - the extra weight is all high, no good for CG, so hard to adapt to cars
Packaging - It is a tall heavy engine - again maybe target use is SUVs and Trucks.


Turn it on its side? Subaru does it.(kinda)


Thought of that option too. Just think it becomes a packaging issue with current platforms - interference with frames and suspension components. A ground up build could do it, just as Subaru does.
But we're talking billions to redo a platform such as the F150. For what net gain to Ford's bottom line? Not sure.
 
Originally Posted By: Cujet
From what I can find, the older opposed piston designs are not as efficient as modern diesels.


Older non opposed piston designs are not as efficient as modern diesels either. The old opposed piston engine couldn't live in the modern world, but with the technology that has been applied to diesels now, i'm pretty sure they could do well.

The old TS3 was only 202cu in in it's largest form, and were pulling huges loads at the time.
 
Originally Posted By: Shannow
...all ideas, no practicality.

Yep. Practicality becomes real pesky at a certain point.

Originally Posted By: Silk

Older non opposed piston designs are not as efficient as modern diesels either. The old opposed piston engine couldn't live in the modern world, but with the technology that has been applied to diesels now, i'm pretty sure they could do well.

This. I do have doubts about the trade-off between new diesel technologies and the practical drawbacks of an opposed piston engine.
 
Originally Posted By: Cujet
I have to wonder how the computational fluid dynamics aspect plays into greater efficiency.


My engineering thesis was two part...one was flow of air and fuel in a simulated inlet manifold, wet floor, mixing, film speeds etc. Part 2 was to develop a glass cylinder that could take cylinder heads from the J-Car (1.3 to 2.2, SOHC, and DOHC, Cosworth DFV, and the rotary valve head that AE Bishop's were designing for the J Car).

Was for flow visualisation, and to be fitted with an instrumented flow straighter to MEASURE swirl and tumble.

That was 1990... CFD at the time at the University was cutting edge, but extremely low resolution and inertial effects.

Nowadays, with the power of CFD, that test rig would be totally unnecessary.

For the engine in question, they mention piston tops for an effective combustion chamber shape, but would also give them all the information that they need on purging the cylinder without over-purging, "egr" tuning by cylinder residuals, swirl, and what happens to that sworl when the combustion chamber is formed in that last little bit of piston movement.
 
Status
Not open for further replies.
Back
Top