Opposed Piston Opposed Cylinder Engine

[MechAg94]

http://www.engineeringtv.com/video/Opposed-Piston-Opposed-Cylinder

I got this link on email and it looked interesting.  At least it appeared to be a new idea, but somebody that is an engine guy may disagree.
The video had this caption below it which is longer than I thought. 

An extremely lightweight opposed piston opposed cylinder (OPOC) engine has been developed under a Defense Advanced Research Projects Agency (DARPA) program. FEV and Advanced Propulsion Technologies (APT) were asked by the U.S. Army Tank Automotive Research Development and Engineering Center (TARDEC) to modify this engine for heavy-truck applications. Analyzing the two stroke scavenging, the side-injection combustion, and the structure of the key components shows the potential of the OPOC concept. It is predicted for the 465 kW (650 hp) OPOC truck engine. The OPOC engine was designed to be modular. Each module is self-contained and delivers 325 hp. The modules are connected together via the Modular Displacement Clutch, which synchronizes the modules for achieving even firing when both modules are functioning. With an optimized scavenging process, the special design features of the OPOC engine offer a significant step towards the potential of the two-stroke engine having double the power density of a four-stroke engine. An estimated 90% scavenging efficiency has been achieved with unique gas exchange characteristics of the OPOC engine and the use of an electric assisted turbocharger. The OPOC engine runs with almost two times the engine speed (3800 rpm) along with a large cylinder stroke (167.53 mm), as a result of the split stroke of the opposed piston structure. This also improves the power density by another factor of 2.

Hosted by: Lee Teschler Videography by: Curtis Ellzey Edited by: Curtis Ellzey

[Northwoods]

There's opposed piston designs dating back to the 1930's IIRC.  It has it's advantages in that there's no top end to have problems with, or weigh things down.  And it produces great power for the dispacment.  But, it has some downsides.  One is how to ensure equal force is applied to each piston in the cylinder, and another is how to exhaust the burned fuel.  Not insurmountable, but not trivial either.

[HeroHog]

Been around a LONG time in big Navel ships as diesel Marine engines I am afraid!

I watched the video and am very impressed with what they have done with the concept! The old ones had a crankshaft at either end of the cylinder where this single shaft design eliminates a ton of shafts, gears and balance issues! The electronically assisted turbos intrigue me as well!

[drewtam]

The spokesmen for this product were pretty good. They knew what they were talking about. [No 150mpg carburettors here / they aren't snake oil salesmen.]

In the video, he quoted 220 g/kwhr efficiency. He claims to having demonstrated power, fuel consumption, smoke number, and weight.

220g/kwhr is equivalent to a well designed diesel meeting Tier 3 or Tier 4 non road emissions (or 2004 & 2007 on high way truck engine emissions). He has not demonstrated emissions compliance. I would expect that meeting emissions compliance would dramatically reduce fuel efficiency. For example, a non-regulated, well designed, modern technology diesel can easily hit ~190 g/kwhr. So on that apples to apples emissions basis, this engine is already 15% behind. So it seems the efficiency will be less than a typical modern diesel but much better than a gasoline.

Additional risk is whether this engine can be tuned to hit current emissions regulations at all. (Not impossible, but high risk). I am not as familiar with 2-stroke diesels, but I think they have trouble with PM & HC emissions.

[230RN]

Just looking at the pic on the cited site, it looks like the Deltic Diesel engine is a sort of wrapped around version of it sans the long connecting rods.



(2-cycle diesel)

And somebody's bound to bring up this site sooner or later, so I might as well be the somebody and sooner might as well be now:

http://fastjeff57.tripod.com/

^ Fascinatin' stuff.

I suppose the most efficient way of getting expanding gas to yield motive power, would be to put the vehicle itself into a cylinder and blow up some fuel mixture behind it so the expanding gases drive the vehicle out the cylinder directly.

Like this, see, 'cept horizontal and with deployable wheels:



Terry, 230RN

(Pic credits in properties)

[TommyGunn]

......Like this, see, 'cept horizontal and with deployable wheels:



Terry, 230RN

(Pic credits in properties)

Needs detcord. 

[Angel Eyes]

Been around a LONG time in big Navel ships as diesel Marine engines I am afraid!

Yep, Fairbanks-Morse made a lot of opposed-piston engines for marine use, then got into locomotive building post-WWII.

http://en.wikipedia.org/wiki/Fairbanks-Morse

[RoadKingLarry]

Yep, Fairbanks-Morse made a lot of opposed-piston engines for marine use, then got into locomotive building post-WWII.

http://en.wikipedia.org/wiki/Fairbanks-Morse

We had opposed piston F-M diesel gens on subs, still do I imagine.

[HeroHog]

I first learned of the FM opposed piston Diesels at "C" school at the Great Lakes Naval base in the mid 70s. I spent most of my Naval career as a Diesel Engineman working on the 12-278A GM Diesels that were also in common use in many locomotives. I also was always around various n-71 GM Diesels. I was on an ASR, a Submarine Salvage and Rescue ship... basically an ocean going Tugboat! We had 4 12-278a's for main propulsion and a handfull of 6-71s for axillary power and some 4-71s and even 2s in the whale boats.

The 1st number is the number of cylinders and the number after the hyphenen is the cubic inches per cylinder!

[Owens]

Interesting twist on an opposed piston engine. 2 cylinders, but 4 pistons that oppose in sets.

[kgbsquirrel]

The 1st number is the number of cylinders and the number after the hyphenen is the cubic inches per cylinder!

And the letter that follows the number after the hyphen?

[HeroHog]

And the letter that follows the number after the hyphen?

THAT I do NOT know!

[CNYCacher]

I find this design fascinating, especially the fact that they have the two pistons opposing each other from the same shaft, which produces net zero force on the main shaft bearings.  Most IC engines have tremendous forces acting against the shaft bearings at all time, and the block needs to be beefier because of that.

[drewtam]

An I6 or any flat engine achieves the same thing.

All of these still have some main bearing load. The balancing forces don't act through the same vector, the pistons, or in this case, the con rods are offset.

[bedlamite]

It's an incremental improvement, and we will probably see more of this type engine. But even with the 20some million that Bill Gates gave them last year they've only managed to get into generators so far. They still haven't met auto emissions requirements yet.

[CNYCacher]

An I6 or any flat engine achieves the same thing.

I don't see how.  The explosive forces are always forcing the piston to push against the main bearings.  Rotation is generated by attempting to make the cylinder head and main bearing fly away from each other.  They hold together though, and rotation is created by a combination of rotational inertia and the offset of the connecting rods.  The main bearings on the bottom of the crank journals must bear the brunt of the explosive force, as well as the inertial forces of the piston changing directions at BDC.  The main bearing on the top of the crank journals must bear the force of the vacuum on the intake stroke, as well as the inertial forces of the piston weight changing direction at TDC.

None of that really applies here.  Instead, the push-pull setup cancels out and really only makes rotational force between the engine body and the shaft.

All of these still have some main bearing load. The balancing forces don't act through the same vector, the pistons, or in this case, the con rods are offset.

[Scout26]

Everything old is new again....

[drewtam]

I don't think I can describe the balance of an I6 or flat engine using text. But these engines always have a set of mass counteracting the forces on the crank, through the crank.
Whenever there is a downward force (either from countering inertia or cylinder pressures); there is also an upward force somewhere else on the crank.

This also might help explain in it...
http://www.autozine.org/technical_school/engine/smooth3.htm