5 ms·

Opposed-Piston Engine

51 points by acd 12y ago

cstross 12y ago
See also the Junkers Jumo 2014: http://en.wikipedia.org/wiki/Junkers_Jumo_204 http://en.wikipedia.org/wiki/Junkers_Jumo_204 And its descendant, the Napier Deltic engine: http://en.wikipedia.org/wiki/Napier_Deltic http://en.wikipedia.org/wiki/Napier_Deltic And in particular, the animation of the Deltic layout (three cylinders, three crankshafts (one of them contra-rotating), six(!) pistons): http://en.wikipedia.org/wiki/Napier_Deltic#mediaviewer/File:Napier_Deltic_Animation.gif http://en.wikipedia.org/wiki/Napier_Deltic#mediaviewer/File:... (Opposed piston engines aren't exactly new.)
- agumonkey 12y ago
  Not new but first time I see them (even though it's so obvious I feel stupid). So many engines geometries and configuration, it's beautiful. Thanks ps: old reddit thread for other designs http://www.reddit.com/r/technology/comments/82gqi/six_pistons_three_cylinders_three_crankshafts/ http://www.reddit.com/r/technology/comments/82gqi/six_piston...
  - tankenmate 12y ago
    The reason they aren't more common is because many people tried, but without high precision parts and extensive dynamic analysis it is very difficult to make them work reliably. Have a look at the Deltic, it was very powerful for its size and weight, but was a maintenance nightmare; in both of its major applications, high speed naval patrol boats and high speed trains. The major breakthrough with the dynamics on the Deltic was the one contra rotating crank.
JeanSebTr 12y ago
«To play the animation, please click the arrow located in the center of the image below.» That's the most hand-holding approach I've read telling me to play a video.
papaf 12y ago
Can anyone recommend any books on the design of combustion engines? I am looking for a text book that would be approachable to someone without an engineering background although comfortable with undergraduate level mathematics.
- auxym 12y ago
  A relatively short but complete book I'd recommend would be Ferguson & Kirkpatrick's "Internal Combustion Engine". It was used in an undergrad engines course I did. The classic, big textbook, AFAIK, is John Heywood's (MIT Prof) Internal Combustion Engine Fundamentals. These books give you a general understanding of the functioning of ICEs. For practical design considerations, I've found "Internal Combustion Engine in Theory and Practice" by Charles F. Taylor interesting. There's a lot of other books on specific aspects of design, look for example at books published by the SAE. I'm not sure exactly how much one would get from going through a book like Ferguson without basic notions in physics (basic thermodynamics, dynamics, fluid mechanics, materials). I think a motivated individual could certainly supplement as he goes using wikipedia as a starter for things he does not understand. No advanced knowledge of these topics is needed, as I said, just the basics.
ferongr 12y ago
The animation shows a turbocharger but it also shows that the engine operates on a 2 stroke cycle. Conventional wisdom would say that the turbocharger would be a waste since both intake and exhaust ports are open at the same time, preventing the compression of the mixture, while at the same time potentially wasting some of it as it is forced out of the exhaust port. I'd speculate that the turbocharger is small enough and used mainly to introduce the mixture into the chamber with enough velocity to make it swirl, while at the same time improving the removal of exhaust gases.
- ams6110 12y ago
  On large two-stroke engines a blower/turbocharger is often used to not only introduce additional fresh air for the next combustion cycle but also to more rapidly/completely purge the combustion gasses out the exhaust ports (this is called scavenging).
  - semerda 12y ago
    It's not just air, its usually compressed air above atmospheric sea level (bar+). This opposed-piston architecture appears more complicated. Adding an additional crankshaft isn't a small feat. Removing valves that rely on the rotation of a crankshaft is a small win. Add bar+ of pressure into a combustion motor like this and watch it pop. Too many moving pieces! But saying this, what is the drive to keep on overcomplicating things like traditional combustion motors? The Wankel engine was simple, small & powerful (when a turbo hanged off it). The industry killed it to replace it with a more complicated piston engine. And now this more complicated architecture proposal. I would love to see engineering innovation focusing on simplification like that which exists in electric motors. There is still so much more that can be done with magnets & coils.
    - Gravityloss 12y ago
      Emission controls have become a lot stricter. In heavier engines, they are the major technology driver now. Wankels have a crescent shaped combustion space. That is bad for emissions as the far away thin corners dont burn so well.
mpweiher 12y ago
There's also http://www.ecomotors.com http://www.ecomotors.com . Their main engine guy, Prof. Hofbauer, was a neighbor in Wolfsburg, he was in charge of VW engines at the time. Brilliant engineer. (No association apart from the neighbor thing). They claim 100 mpg cars are possible with their engine.
Shivetya 12y ago
any reason to use an exhaust driven turbo? I would expect an electric turbo could offset the need to have multiple cylinders for synchronizing the exhaust pulses
- auxym 12y ago
  Generally speaking the tradeoff is less steps in energy conversion means better efficiency, and less needed machinery (electric generator, motor, perhaps gearbox of sorts, perhaps battery), meaning less costs, weight and more reliability.
a-b 12y ago
A lot of tanks has opposed engines https://en.wikipedia.org/wiki/Opposed-piston_engine https://en.wikipedia.org/wiki/Opposed-piston_engine main reason - "flat" configuration
larrydag 12y ago
I'm no mechanical engineer but doesn't two crank shaft decrease efficiency quite a bit? Also introduces a lot more moving parts.
- auxym 12y ago
  Crankshaft frictional losses are typically the smallest of the friction losses in a engine, the others being cylinder/ring friction and the valve train (you could also include accessories and pumping). You can play around with the applet at http://www.wiley.com/college/mechs/ferguson356174/apps/friction/friction.html http://www.wiley.com/college/mechs/ferguson356174/apps/frict... [1] to verify this. You are right that it introduces more parts (weight, costs, reliability), which I guess is one of the reasons we haven't seen its adoption.
deleted 12y ago
[deleted]
fnordfnordfnord 12y ago
This is what I can't wait for. free piston generator engine https://www.youtube.com/watch?v=QUbBqSu9Hdc https://www.youtube.com/watch?v=QUbBqSu9Hdc

51 points by acd 12y ago

See also the Junkers Jumo 2014: http://en.wikipedia.org/wiki/Junkers_Jumo_204 http://en.wikipedia.org/wiki/Junkers_Jumo_204 And its descendant, the Napier Deltic engine: http://en.wikipedia.org/wiki/Napier_Deltic http://en.wikipedia.org/wiki/Napier_Deltic And in particular, the animation of the Deltic layout (three cylinders, three crankshafts (one of them contra-rotating), six(!) pistons): http://en.wikipedia.org/wiki/Napier_Deltic#mediaviewer/File:Napier_Deltic_Animation.gif http://en.wikipedia.org/wiki/Napier_Deltic#mediaviewer/File:... (Opposed piston engines aren't exactly new.)

agumonkey 12y ago
Not new but first time I see them (even though it's so obvious I feel stupid). So many engines geometries and configuration, it's beautiful. Thanks ps: old reddit thread for other designs http://www.reddit.com/r/technology/comments/82gqi/six_pistons_three_cylinders_three_crankshafts/ http://www.reddit.com/r/technology/comments/82gqi/six_piston...
- tankenmate 12y ago
  The reason they aren't more common is because many people tried, but without high precision parts and extensive dynamic analysis it is very difficult to make them work reliably. Have a look at the Deltic, it was very powerful for its size and weight, but was a maintenance nightmare; in both of its major applications, high speed naval patrol boats and high speed trains. The major breakthrough with the dynamics on the Deltic was the one contra rotating crank.

JeanSebTr 12y ago

«To play the animation, please click the arrow located in the center of the image below.» That's the most hand-holding approach I've read telling me to play a video.

papaf 12y ago

Can anyone recommend any books on the design of combustion engines? I am looking for a text book that would be approachable to someone without an engineering background although comfortable with undergraduate level mathematics.

auxym 12y ago
A relatively short but complete book I'd recommend would be Ferguson & Kirkpatrick's "Internal Combustion Engine". It was used in an undergrad engines course I did. The classic, big textbook, AFAIK, is John Heywood's (MIT Prof) Internal Combustion Engine Fundamentals. These books give you a general understanding of the functioning of ICEs. For practical design considerations, I've found "Internal Combustion Engine in Theory and Practice" by Charles F. Taylor interesting. There's a lot of other books on specific aspects of design, look for example at books published by the SAE. I'm not sure exactly how much one would get from going through a book like Ferguson without basic notions in physics (basic thermodynamics, dynamics, fluid mechanics, materials). I think a motivated individual could certainly supplement as he goes using wikipedia as a starter for things he does not understand. No advanced knowledge of these topics is needed, as I said, just the basics.

ferongr 12y ago

The animation shows a turbocharger but it also shows that the engine operates on a 2 stroke cycle. Conventional wisdom would say that the turbocharger would be a waste since both intake and exhaust ports are open at the same time, preventing the compression of the mixture, while at the same time potentially wasting some of it as it is forced out of the exhaust port. I'd speculate that the turbocharger is small enough and used mainly to introduce the mixture into the chamber with enough velocity to make it swirl, while at the same time improving the removal of exhaust gases.

ams6110 12y ago
On large two-stroke engines a blower/turbocharger is often used to not only introduce additional fresh air for the next combustion cycle but also to more rapidly/completely purge the combustion gasses out the exhaust ports (this is called scavenging).
- semerda 12y ago
  It's not just air, its usually compressed air above atmospheric sea level (bar+). This opposed-piston architecture appears more complicated. Adding an additional crankshaft isn't a small feat. Removing valves that rely on the rotation of a crankshaft is a small win. Add bar+ of pressure into a combustion motor like this and watch it pop. Too many moving pieces! But saying this, what is the drive to keep on overcomplicating things like traditional combustion motors? The Wankel engine was simple, small & powerful (when a turbo hanged off it). The industry killed it to replace it with a more complicated piston engine. And now this more complicated architecture proposal. I would love to see engineering innovation focusing on simplification like that which exists in electric motors. There is still so much more that can be done with magnets & coils.
  - Gravityloss 12y ago
    Emission controls have become a lot stricter. In heavier engines, they are the major technology driver now. Wankels have a crescent shaped combustion space. That is bad for emissions as the far away thin corners dont burn so well.

mpweiher 12y ago

There's also http://www.ecomotors.com http://www.ecomotors.com . Their main engine guy, Prof. Hofbauer, was a neighbor in Wolfsburg, he was in charge of VW engines at the time. Brilliant engineer. (No association apart from the neighbor thing). They claim 100 mpg cars are possible with their engine.

Shivetya 12y ago

any reason to use an exhaust driven turbo? I would expect an electric turbo could offset the need to have multiple cylinders for synchronizing the exhaust pulses

auxym 12y ago
Generally speaking the tradeoff is less steps in energy conversion means better efficiency, and less needed machinery (electric generator, motor, perhaps gearbox of sorts, perhaps battery), meaning less costs, weight and more reliability.

a-b 12y ago

A lot of tanks has opposed engines https://en.wikipedia.org/wiki/Opposed-piston_engine https://en.wikipedia.org/wiki/Opposed-piston_engine main reason - "flat" configuration

larrydag 12y ago

I'm no mechanical engineer but doesn't two crank shaft decrease efficiency quite a bit? Also introduces a lot more moving parts.

auxym 12y ago
Crankshaft frictional losses are typically the smallest of the friction losses in a engine, the others being cylinder/ring friction and the valve train (you could also include accessories and pumping). You can play around with the applet at http://www.wiley.com/college/mechs/ferguson356174/apps/friction/friction.html http://www.wiley.com/college/mechs/ferguson356174/apps/frict... [1] to verify this. You are right that it introduces more parts (weight, costs, reliability), which I guess is one of the reasons we haven't seen its adoption.

deleted 12y ago

[deleted]

fnordfnordfnord 12y ago

This is what I can't wait for. free piston generator engine https://www.youtube.com/watch?v=QUbBqSu9Hdc https://www.youtube.com/watch?v=QUbBqSu9Hdc