interesting engine concept

CrabbyMilton · January 16, 2017, 03:40:08 PM

Idea is interesting but I wonder how it would be accepted.
I like the music though.

https://www.youtube.com/watch?v=JoQkTIfAB2U

Iceni John · January 16, 2017, 04:36:21 PM

It's deja vu all over again - Commer TS3 meets Fairbanks-Morse. Interesting, but hardly new. I wonder what happened to that opposed-piston design a few years ago using pull rods for each cylinder's outer piston? Maybe if we wait long enough, someone will reinvent the Detroit 2-stroke! (Oh wait, Foden and Nissan did . . .)

John

blue_goose · January 17, 2017, 05:05:51 AM

There were lots of those on Subs back in the 30's, 40 and 50
Jack

CrabbyMilton · January 17, 2017, 05:18:05 AM

I found an article that some startup group was developing a locomotive that would burn coal or wood thereby creating steam. Then the steam...Oh wait, I think they had done that before never mind. I think I found that on the same site that was talking about BOEING offering a piston version of the 787.

TomC · January 17, 2017, 08:14:43 AM

To this day, most all submarines and naval ships still use the Fairbanks-Morse opposed piston engine for standby power. But it is also huge- 8 1/8" bore x 10" stroke for each crank, so 8 1/8" bore x 20" effective stroke and up to 12 cylinders in line.
Achates engine is already testing a 3 cylinder engine. If they made a 6 cylinder version, it would put out 550hp and 1620lb/ft torque-perfect for trucks and buses. I'm anxiously waiting their production. I know the military is very interested also. Good Luck, TomC

DoubleEagle · January 17, 2017, 08:52:43 AM

The Achates website shows a lot of important investors and many highly educated people behind the research. This redesign of an old idea might become big someday if the design really delivers what they are hoping for. The middle of the liner sure looks like something out of a Detroit 2 cycle. The key thing is how good it sounds when going through the gears (at least for those of us who love the sound of Detroit Diesels).

Brassman · January 17, 2017, 12:17:29 PM

Those OP engines were 2-strokes.

chessie4905 · January 17, 2017, 05:51:04 PM

Fairbanks-Morse also built locomotives with this type of engines. They had problems with this engine design and they later left locomotive market.

http://www.american-
rails.com/fairbanks-morse-locomotives.html

http://www.rypn.org/forums/viewtopic.php?f=1&t=7849&start=0

Iceni John · January 17, 2017, 06:22:45 PM

Quote from: Brassman on January 17, 2017, 12:17:29 PM
Those OP engines were 2-strokes.

Could they be anything else?! I just like the idea of an engine without heads. Let's hope that emissions and fuel economy don't limit their viability - what was acceptable half a century ago may not be acceptable now.

John

Dreadnought · January 30, 2017, 12:21:17 PM

I worked with them and was involved in integrating a similar concept into another drive train.

I have a very good handle on the pros and cons.

Emissions wise- the engine can be made to burn cleanly (or at least as clean as any other 4 stroke diesel).

There isn't a fuel economy advantage. They kept projecting amazing BSFCs dilluding themselves using wildly optimistic assumptions in simulation. When it came time to build hardware- the engine achieved a Breat Thermal Efficiency of 43% (about 194 g/kwh) while they always claimed/boasted 175 g/kwh/48% BTE was achievable. 43% is nothing special and other heavy duty engines can get closer to 45-49% at best point. They also made a 3 cylinder with extra large cylinders and their test engine wasn't proven to a heavy duty durability schedule. The industry norm is in line 6, I'm sure with extra attention (and cost) the 4 stroke figures could be improved upon with none of the risk.

The biggest problem is the excessive friction of having a long stroke combined with long skirts of the piston to get the correct port timing.

The biggest advantage a 2 stroke like that has is specific power (over a 4 stroke) . But one must ask- why opposed piston? Why not go with the Detroit Diesel style of 2 stroke?

There are claimed advantages in terms of faster combustion burn- but I view that with the correct skepticism - as warrented earlier by their ridiculous efficiency claims. If there is a faster burn- the burn of a 4 stroke can be made faster through some optimization with far less risk, and in practice, how much real world benefit does a faster burn give? Once you add pilot injection to slow the burn down for better refinement- you can only focus on the faster burn late in the cycle anyway.
The biggest difference between the Detroit Diesel style vs the opposed piston 2 stroke- aside from the extra friction of the OP unit, is that extra heat goes out of the exhaust on the OP while on the DD style it goes into the coolant. After a while you get tired of the lies

So in summary- smoke and mirror such that they can syphon extra funds from Pal Alto financial company and have a great extended vacation in San Diego!

TomC · February 02, 2017, 10:09:24 AM

Opposed piston-you get twice the piston stroke than a normal single piston per cylinder engine. Piston stroke is key to fuel economy. Some say an opposed piston will be naturally 20% more fuel efficient than the most fuel efficient 4 stroke. That means, if now, big rig trucks properly equipped and driven are now getting 8mpg at 80,000lbs, the oppposed piston could get 9.6mpg. Based on 120,000mi per year and $3.00/gal fuel, that would mean a savings of $7,500 a year! Good Luck, TomC

Iceni John · February 02, 2017, 10:39:56 AM

Quote from: TomC on February 02, 2017, 10:09:24 AM
Opposed piston-you get twice the piston stroke than a normal single piston per cylinder engine. Piston stroke is key to fuel economy. Some say an opposed piston will be naturally 20% more fuel efficient than the most fuel efficient 4 stroke. That means, if now, big rig trucks properly equipped and driven are now getting 8mpg at 80,000lbs, the oppposed piston could get 9.6mpg. Based on 120,000mi per year and $3.00/gal fuel, that would mean a savings of $7,500 a year! Good Luck, TomC

Isn't each piston moving the same distance as a regular engine's? Yes, the space between the two pistons is twice as big as the space between a piston and its head, but that space is the equivalent of two cylinders. Or am I thinking all cattywampus?

I've also heard about the theoretical advantages of an OP design, but isn't it based more on better thermal efficiency by not having heads? I still think the concept has plenty more miles to run (so to speak). I wish we can see a real-life OP engine soon instead of these nebulous concepts more focused on attracting venture capital than anything else. Let's hope however that any new OP engine is not as noisy as the venerable Commer TS3 - I can still clearly recollect once being in a TS3-powered Commer bus in the late 1960s or early 1970s, and you could barely hear yourself think if you were sitting near the engine's doghouse. Maybe that's where I nurtured my interest in 2-stroke diesels?

John

Dreadnought · February 03, 2017, 06:40:11 AM

Quote from: TomC on February 02, 2017, 10:09:24 AM
Opposed piston-you get twice the piston stroke than a normal single piston per cylinder engine. Piston stroke is key to fuel economy. Some say an opposed piston will be naturally 20% more fuel efficient than the most fuel efficient 4 stroke. That means, if now, big rig trucks properly equipped and driven are now getting 8mpg at 80,000lbs, the oppposed piston could get 9.6mpg. Based on 120,000mi per year and $3.00/gal fuel, that would mean a savings of $7,500 a year! Good Luck, TomC

The key to fuel economy is a thermodynamically optimized chamber- which means a low chamber surface area to volume ratio. Too long a stroke and the friction goes up. Engine friction goes up by the Square of mean piston speed. This is exacerbated on a 2 stroke with piston ports as the skirts have to be extended which further increases engine friction. I'm not sure where the 20% number comes from. As indicated by the quoted measured BSFC numbers- this is a direct measure on a dyno of the fuel efficiency of the engine- there is very little benefit of the 2 stroke vs the 4 stroke to date.

TomC · February 04, 2017, 08:48:50 AM

The two main reasons that 2 stroke engines are so noisy is-one from the blower which is easy to silence with a good air cleaner. And two compression noise which will be quieted from using the new common rail fuel injection with it's mulitple injection per power stroke. Just look how quiet the full size Diesel pickups are now. Good Luck, TomC

daddysgirl · February 04, 2017, 11:57:30 AM

Quote from: Dreadnought on January 30, 2017, 12:21:17 PM
I worked with them and was involved in integrating a similar concept into another drive train.

I have a very good handle on the pros and cons.

Emissions wise- the engine can be made to burn cleanly (or at least as clean as any other 4 stroke diesel).

There isn't a fuel economy advantage. They kept projecting amazing BSFCs dilluding themselves using wildly optimistic assumptions in simulation. When it came time to build hardware- the engine achieved a Breat Thermal Efficiency of 43% (about 194 g/kwh) while they always claimed/boasted 175 g/kwh/48% BTE was achievable. 43% is nothing special and other heavy duty engines can get closer to 45-49% at best point. They also made a 3 cylinder with extra large cylinders and their test engine wasn't proven to a heavy duty durability schedule. The industry norm is in line 6, I'm sure with extra attention (and cost) the 4 stroke figures could be improved upon with none of the risk.

The biggest problem is the excessive friction of having a long stroke combined with long skirts of the piston to get the correct port timing.

The biggest advantage a 2 stroke like that has is specific power (over a 4 stroke) . But one must ask- why opposed piston? Why not go with the Detroit Diesel style of 2 stroke?

There are claimed advantages in terms of faster combustion burn- but I view that with the correct skepticism - as warrented earlier by their ridiculous efficiency claims. If there is a faster burn- the burn of a 4 stroke can be made faster through some optimization with far less risk, and in practice, how much real world benefit does a faster burn give? Once you add pilot injection to slow the burn down for better refinement- you can only focus on the faster burn late in the cycle anyway.
The biggest difference between the Detroit Diesel style vs the opposed piston 2 stroke- aside from the extra friction of the OP unit, is that extra heat goes out of the exhaust on the OP while on the DD style it goes into the coolant. After a while you get tired of the lies

So in summary- smoke and mirror such that they can syphon extra funds from Pal Alto financial company and have a great extended vacation in San Diego!

IDK enough but to be dangerous, but have you seen this?

https://www.youtube.com/watch?v=SL1uwRtqPWE