We've had no shortage of opposed piston engines over the years, but this team is aiming for substantial efficiency gains, as much as 50%, over previous attempts with a design utilizing gasoline compression ignition. The Argonne National Laboratory is working with Achates Power, Inc., and Delphi Automotive on the project to create a "super engine."
As the pistons reverse course and slide to opposite ends of the cylinder, ports machined into the cylinder allow exhaust gases to escape while fresh air is taken in, then the pistons move together again to compress and ignite in a two-stroke cycle. The design eliminates cylinder heads — which are a major cause of heat loss and inefficiency in conventional engines — and allows the engine to run with diesel-like efficiency and power, while maintaining gasoline's emissions benefits.
An analysis by Achates Power indicates the new engine will yield fuel efficiency gains of more than 50 percent compared with a downsized, turbo-charged, direct-injection gasoline engine, while reducing the overall cost of the powertrain system.
I like the concept and it looks promising, but the proof is in the actual engine. After seeing so many positive reports on the EcoMotors OPOC engine, the Cleeves Cycle from Pinnacle Engines, the CoAxe Opposed Piston Diesel and many others, it's hard to get too excited over one more, at this point a running engine demonstrating the performance and efficiency the researchers say they can achieve would be the game changer. I do hope one of these engines finally makes it, maybe this will be the one.
Frits Overmars says
I applaude this new two-stroke Super Engine, but it comes a bit late – 84 years late to be exact:
http://www.deutsches-museum.de/en/collections/machines/power-engines/combustion-engines/diesel-engines/vehicle-and-small-diesel-engines/aircraft-engine-opposed-piston-engine-jumo-205-1932/
Paul Crowe says
If you check a few of our other posts on opposed piston engines, we’ve discussed a lot of earlier examples in the comments. It’s an old idea, but they keep coming back with some type of improvement in the hopes of doing it better than before. I hope they do, but as I note above, we’ll just have to wait and see.
Mike says
Yeah. And I invented it again in high-school back in 1986 when I was 15. My teacher thought it was a fabulous idea, but Junkers Jumo. I was blown away and quite a bit dishearted to discover this.
It has been the bane of my mech eng career to find that I am a century too late every goddamn time. Frederick Lanchester. Buckminster Fuller.
My engine had a unique feature, though: one crank rotates with half the speed of the other, so there is a four-stroke cycle through two-stroke-type ports.
Still needs supercharging to breathe in the right direction, though. And probably reed valves too.
Paulinator says
I’ve seen a few museum examples of the 80 year old Junkers aero-diesel engines that are identical to this “new” technology. They took a page out of OPOC’s playbook. The effort appears to be about mining grants, rather than developing a viable product.
Paul Crowe says
Once they start working those “grant mines” and find a few they just keep digging. I wonder if they’ll ever be exhausted.
Buck says
If performance is the goal, and recognizing that there is nothing new under the sun, a Delta configuration, as used successfully by Napier, that is three cranks in a triangle with a cylinder bank between each pair of cranks, could pack a lot of engine into the available space.
GenWaylaid says
I suppose it stands to reason that if you can get enough control to have gasoline compression ignite, then any design that works well for diesel engines can be applied.
I have no doubt that Argonne et al. can make this engine burn little gasoline for the power produced, but I doubt they’ll burn little enough oil to meet modern vehicle emissions standards. Any design that relies on piston ports will burn some oil because the piston rings need to carry lubrication all the way across the port.
Cylinder heads with poppet valves may lose a lot of heat, but I’ve never seen a better way to separate combustion from lubrication.
Bob says
The drawing above shows 2 rings on the piston skirt – I’m guessing that addresses the port oiling concern?
Ricardo Juarez says
The new items in this engine seem related to the research on the combustion “mechanics” and what seems a thorough and extensive study simulation of the processes going on after ignition. Of course the self ignition of gasoline is very important. The honda EXP-2 2stroke used “autoignition” of the mixture at certain rpms continuing without the need of a spark and was reported as a very efficient combustion. The question is if this self-combustion of gasoline can be produced with direct injection in ordinary high compression engines. I believe it has been done but in that case why is it not applied regularly to 4 stroke engines ? Personally i love 2 stokes and would find exciting if this process could be adapted to the old “twingle” concept on motorbikes but now with independent lubrication (and a compressor).
sam says
All of the negative comments are quite surprising. I see no ‘grant mining’ here. Achates have successfully manufactured a 3 cylinder opposed piston diesel engine and it’s taken them a heck of a long time to do so. They have in excess of 6000 hours of runtime on it as per their website. They have gone to the trouble to get their results verified and explain in detail the work they’ve done to get around historical issues with opposed piston engines, namely oil consumption. As I understand it, this was mainly due to excessive piston slap owing to piston pin wear, causing liner degradation. These are purely mechanical issues that Achates have solved over several years. Unlike the Junkers Jumo engines, or the Commer TS3, etc, modern computing power is available. So, regarding the issue of oil ejection out of the exhaust port, by monitoring the pressure in the exhaust manifold it is possible to keep the oil in the piston rings as they move past the port(s). I believe they designed their own tools to monitor pressure in between the piston rings in order to do that, so they can see what’s going on. That is scratching the surface on the work they have done, and I’ve probably explained it wrong as it frankly baffles me how ingenious some of the work they’ve done is, but I am confident that at some time, these engines will make it into production. They aren’t like any of the other companies mentioned, as they appear to have a great deal of commercial awareness looking at the things dr James Lemke has said, and have gone to great lengths to back up their arguments with actual data from actual units. They’ve also considered the issues of manufacturing their units in large volumes and what kind of tooling is required. Nearly all of the designs I’ve ever seen ignore that.
Incidentally, when testing, the main test unit powered all of it’s ancilliaries including oil pump and I believe alternator. As I understand it, that isn’t always the case.
So I have faith in Achates, and they certainly appear to know what they’re doing, and take great care in doing so; I really look forward to hopefully seeing a heck of a lot more from them.