Achates ? 1

[enginesrus]

I thought a few vehicle manufactures were gearing up to manufacture this engine? What happened? I'm guessing they are trying to use the wrong materials that lack the durability?

 

[BrianPetersen]

Active website suggests they're not broke yet. My own suspicion is that real world testing found that it did not live up to expectations.

 

[j2bprometheus]

Hi- ACHATES claims they are partnering with Cummins for some military application:

http://achatespower.com/achates-pow...pability-for-the-us-army-ground-combat-fleet/

j2bprometheus

 

[dgallup]

Supposedly Formula One is considering them for their next engine architecture. But I'll believe it when I see it.

There are better links but this is the first one I can lay my hands on.

https://www.cycleworld.com/story/bikes/advanced-two-strokes-to-power-formula-1-future/

----------------------------------------

The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[enginesrus]

I would think Fairbanks Morse would be the more likely partner, since they are doing this real time, and have been for the past 80 or so years I think. And they are now at or over the 50% range.
Since those engines are not made from Al, my guess would be the new designs made from Al castings very likely don't hold up. The design is well proven it just has to be done correctly .

 

[BrianPetersen]

It's more likely that the claimed thermal efficiency and emissions benefits did not translate into reality.

A normal diesel-engine combustion chamber has the injector in the center spraying outward. Can't do that with the opposed-piston layout - it can only spray in from the outside. It's probably harder to achieve proper fuel distribution in the combustion chamber. That's not favourable for emissions.

All piston engines rely on piston rings. Those need lubrication. All engines relying on piston-porting inevitably lead to a bit of the lubricating oil getting into the combustion process (if piston-ported intake) or out the exhaust (if piston-ported exhaust). That's bad.

Detroit Diesel gave up on two-strokes for on-road applications when faced with 1990s-era emission standards, and those standards are tougher today.

Fairbanks-Morse does not build engines for on-road applications ...

 

[btrueblood]

"All engines relying on piston-porting inevitably lead to a bit of the lubricating oil getting into the combustion process" - Brian

This. They mention it in some of their papers and on the website, but there is no mention of how they addressed minimizing it.

 

[EdStainless]

I'll bet that these guys have gone back and read all of the reports for the old Army Adiabatic Diesel program.
As I recall each engine mfg was give a 5yr contact, and it went from one company to the next. Sometime in the late 70's - early 80's I saw one of these on a test stand.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy

 

[Lou Scannon]

Adiabatic engines were still a "hot" topic in the mid 80s, but fizzled out by the 90s IIRC. Apart from the brutal component temperatures and thermal gradients, chief objections were higher NOx due to higher peak flame temperatures, all else being equal, and the unwanted outcome that most of the heat that was retained in the cylinder, due to the hotter surface temperatures, rather than being turned into work, escaped with the exhaust. Whether there was any effort to turn this phenomenon to advantage via Miller timing and higher boost pressure, I have not heard.

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

 

[RodRico]

The Cummins/Achates team was awarded $47.4 million by the National Advanced Mobility Consortium (NAMC) under the Advanced Combat Engine (ACE) project in September 2017, so they've only been working 15 months and it's likely a bit premature to write it off as a failure.

I imagine Cummins' primary contribution is manufacturability and reliability. While Fairbanks Morse might seem a more likely partner than Cummins, Achates may view them as a competitor and thus refuse to team with them. Note that many companies also refuse to bid on government contracts because of the red tape, and Fairbanks Morse isn't listed as a member of the NAMC, so perhaps they simply weren't interested.

The contract is for military applications, so emissions likely weren't a factor in the Army's award. They would likely be more concerned with power density (power-to-weight, power-to-volume), reliability, field maintainability, efficiency, and oil consumption. I imagine Achates is working hard to get oil consumption down via fine control of oil injection in a fashion similar to Mann and Wartsila.

The contract awarded to the Cummins/Achates team is for research and development, so it's a given that there is work to do. In the end, the engine could "work" but fail to meet any one or more of the government's objectives and thus not be taken into production. Companies tend to be very vocal about their R&D successes and remain silent about their failures. That being said, it's a bit early to tell whether this program is on track or struggling IMHO.

 

[BrianPetersen]

So all we know thus far, is that it is very efficient at extracting money out of government research grants.

 

[RodRico]

Brian, I ran an R&D team working government contracts for a couple of decades, and I assure you no established government R&D partner puts their reputation on the line by proposing completely unfounded concepts; past performance is a heavily weighted evaluation criterion for all such contracts from the government. Cummins certainly doesn't need a few million from R&D and is capable of vetting a diesel engine design, so I think it's safe to assume they had reasonable expectations of success before teaming with Achates and proposing their technology.

 

[turbomotor]

One of the drawbacks of any uniflow scavenged 2 stroke engine is the design of an efficient charge air system. Achates may recognize that problem, and that may be why they have partnered with Super Turbo.

https://www.superturbo.net/media/articles/article-22/

 

[RodRico]

turbomotor,

This sounds complex and costly: "The SuperTurbo is a fully mechanical driven turbocharger that provides the benefits of supercharging, turbocharging and turbo-compounding in one device."

I use a third piston to form a charge pump used to scavenge and charge my opposed pistons. The ports are large so I can keep pressure down around one tenth bar (to minimize pumping loss) and reduce required ring tension in the air pump (to reduce friction loss). All told, the charge pump is responsible for so little loss, it really has virtually zero impact on performance. It does, however, increase engine size (the charge pump bore and stroke is the same as that of the opposed piston pair).

Rod

 

[turbomotor]

Thanks for the info on your very interesting charge pump. Does the charge pump discharge just depend on porting to manage the exit flow, or are you using reed valves?

And I agree, the SuperTurbo sounds OK on paper, but there are a number of technologies that have not been proven to have high durability (such as very high speed planetary traction drive). I have read stories about a similar technology used on the automotive aftermarket (Rotrex Supercharger), but I have yet to hear of one of these installations that makes it past 100k kilometers.

 

[RodRico]

The only flow controls associated with the entire scavenge/charge system are the intake and exhaust ports in the main cylinder and a face port controlling intake to the charge pump. Everything is cam driven, so I have fine control over timing constrained only by acceleration, jerk, and material stress. The charge pump piston doesn't move unless the intake and exhaust ports are wide open (the exception being a brief 3 degree period when Atkinson operation may have the charge pump increasing volume at precisely the same rate the opposed pistons are decreasing volume, thus reducing intake volume without much pumping loss). My continuation patent is finally filed, so I may post some figures in a separate thread to collect a final round of feedback before cutting metal.

The turbo selected by Achates seems as complex and costly as the entire engine. It seems inelegant, and that bugs me.

 

[gruntguru]

The turbo selected by Achates seems as complex and costly as the entire engine. It seems inelegant, and that bugs me.

Agree. Can't imagine why Achates would blur the whole concept introducing another unknown when an off-the-shelf turbo will do the job. Unless of course they are looking for a diversion?

je suis charlie

 

[TugboatEng]

EMD has been using high speed planetary drives on their turbochargers since the 1960's. I believe the gear drive runs the turbocharger up to around 25,000 rpm before the turbine wheel produces enough power to override the overrunning clutch.

 

[turbomotor]

I have heard of this approach that EMD uses on their two stroke engines (I think?), but I have never studied it. Now that CAT owns EMD, I wonder if they plan to use the planetary drive and overrunning clutch approach to some of their large (Lafayette) four stroke stationary engines that need to come up on-line for emergency power generation in a very quick manner.

 

[RodRico]

turbomotor, note I have published a Solidworks animation of my opposed piston and charge pump set-up under a different thread.