I’ve started a number of companies in my career, in several different industries. While I took my Ph.D. in theoretical physics, I’m a pretty applied guy—I tend to look for new ways to solve problems. In addition to being a physicist, I’m also a private pilot with more than 7,000 hours of flying time. I’ve flown a number of different planes over the years. A multi-engine plane, of course, has the advantage of allowing a pilot to continue flying if one engine fails, but the vast majority of private pilots fly single-engine planes. I began to wonder if there was a way to design an engine that is both light and fuel efficient so that two could be ganged together to drive a single prop, combining the fault resiliency of a twin-engine plane while reducing cost and asymmetrical thrust.
When I went on a beach vacation in 1998, I took Charles Taylor’s two-volume book on internal combustion engines and learned about the Junkers Jumo 205/207 engines of the 1930s and 40s. These opposed-piston, two-stroke, diesel aviation engines set benchmarks for fuel efficiency and power density that still, in combination, have not been matched. The challenge, however, lay in the ability to make the historically efficient and power dense opposed-piston architecture meet modern emissions and durability standards—which it had failed to do since the 1970 passage of the U.S. Clean Air Act.
Never one to shy away from a challenge, I began trying to solve this problem with Bill McHargue, a fellow physicist, in 1998. My inspiration was wondering what Junkers could have done with today’s engine technology—high-pressure common-rail fuel injectors, supercomputers, chemically reactive computational fluid dynamics, computer-aided engineering, advanced materials and lubricants, and sulfur-trace oil measurement tools.
By 2004, we made enough progress on improving the original Junkers design that we formed Achates Power, in partnership with fellow pilot, and friend, John Walton. True to my original focus of developing a more fuel-efficient back-up engine for a single-engine plane, I named the company after Achates—a character in Virgil’s epic poem Aeneid and the faithful friend to Aeneas (just as I hoped this engine would be a “faithful friend”).
It didn’t take long to realize, though, that if we created an engine clean enough to meet tough on-highway emissions standards, we could address a much larger market for commercial and passenger vehicles. With a global engine market that tops $300 billion a year and is projected to grow to $525 billion a year by 2020, I knew that the automotive industry is ultimately where we should focus our efforts. Armed with this knowledge, we went about staffing the company with the best and brightest scientists and engineers from the top automotive engine development and manufacturing organizations. We also sought out experts in academia and industry to guide us as part of the Achates Power Technical Advisory Board.
By 2005, we had finished our first engine prototype and had begun testing it in our in-house test cell. A second test cell was added in 2009 and, since then, nearly 3,000 hours of testing have been completed on the initial engine design as well as several other variations.
While I’ve always believed that we’d successfully modernize the opposed-piston, two-stroke engine, even I’m impressed with the level of efficiency gains we’ve witnessed over the last year. These gains, benchmarked against the Ford Power Stroke (considered one of the best medium-duty engines available) have demonstrated:
- More than 20% lower cycle average brake-specific fuel consumption
- Similar engine-out emissions levels meeting the most stringent emissions regulations in the world
- Low fuel-specific oil consumption
- Reduced cost, weight and complexity
Based on these results and our successful discussions with customers and prospects globally, I have no doubt that the Achates Power engine will make it to highways around the world. As new federal standards require an even more significant increase in fuel efficiency and reduction in greenhouse gas emissions, our opposed-piston, two-stroke engine is poised to transform the transportation industry—providing an economically and environmentally sustainable alternative to traditional, hybrid and electric powertrains.
Browsing your website as an outsider first it was not obvious why you named the company Achates Power. At some point in time I thought you refer to the Sicilian hero who discharged his arrow with such a power that it took fire from the friction of the air. (Can it be a hint to the Diesel cycle?) But this gentleman was named Acestes..
Anyhow, the Engine Design Timeline explains the source but up till recently we (the public..) needed the background given in the article above.
A different topic regarding the brake thermal efficiency of the opposed piston engine from Achates Power.
When I was a kid I learnt the hard way the obvious that riding my bicycle on a hilly terrain is much more exhausting than on the flat. Then I bought my first car and that particular model on that particular summer vacation did not have a higher fuel consumption at a drive with a mixture of uphill/downhill than on the plain. Then I learnt that hypermileage (maximizing the mile per gallon) with a stock car on a race actually relies on the pulse and glide technique. Let’s say you’re on a road where you want to go 60 km/h. Instead of driving along at a steady 60, you instead accelerate to 70 (that’s the pulse), and then coast in neutral with the engine off down to 50 (that’s the glide).
Then I learnt that a (well-engineered) parallel hybrid (at least where power comes from the ICE and at acceleration an electric motor provides additional thrust) has a better mileage at a constant speed, despite the several stages of energy transformation than a non-hybrid car with the same total performance. In other words we have mileage improvement even at constant highway speed.
The common denominator in the above mentioned examples can be found and understood by considering a generic efficiency curve for a modern gasoline engine. Its peak brake thermal efficiency is let say 25% but it drops to 15% at a partial load. (Diesels are much better let say 40%/30%, but still with huge differences between operational points.) It means that if I use the full load mode and then I shut off the engine or I downsize the ICE as for the parallel hybrid and I need higher load on the engine for the same external load I can have a significant (well not on the fairy-tale scale) increase in mileage.
When studying the publication from your website (renaissance_of_the_opposed_pistons.pdf, page 9. table 2) we can learn the brake thermal efficiency between A25 to C75 load conditions.
For me the most amazing is how steady the efficiency between the different load points is. I would be pleased to see a full efficiency map and I would also like to learn, if its is public, how you achieved it.
Characterizing this engine by the peak brake thermal efficiency underestimates how efficient it may be once it is built into a real vehicle. I can hardly wait to see it.
Thanks,
Sventin
Sventin:
Thanks for the feedback. As mentioned in the blog post, the source of the company name is from Virgil’s classic poem, Aeneid, about the Trojan Wars. In that poem, Achates was the trusted and loyal friend of Aeneas.
With regards to your question, to estimate the fuel efficiency benefit of our engine in a real vehicle, we use the 13-mode stationary cycle test. This is known as the Supplemental Emissions Test/Discrete Mode Cycle in the U.S., and it is identical to the European Stationary Cycle. We use six of 13 modes in our analysis, with the same weights of the full 13-mode test. The results between our six points (A25, A75, B50, B75, C25 and C75) correlate quite closely to the full 13-mode test, but by focusing on just these six, we can reduce our calibration and testing time by half.
Comparing our measured engine performance—at similar engine-out emissions—to the new Ford Power Stroke 6.7L engine, we have demonstrated a 21% reduction in brake-specific fuel consumption on the drive-cycle average. This is a substantial achievement, particularly considering our opposed-piston engine is less costly to manufacture and is also lighter weight.
Jim
I find this steady indicated thermal efficiency remarkable too. For me this is counterintuitive, because lower load spells lower peak temperature and carnot cycle efficiency is depending strongly on peak temperature.
In the above mentioned table one can see, that lower load actually yields h i g h e r indicated thermal efficiency – if I understand the table correctly.
I’d be thankful if you could drop some lines on that.
Dominik
Dominik:
There are many factors that contribute to indicated thermal efficiency (ITE). While there are ITE advantages to operating at higher loads, there are also several disadvantages.
1.) The heat transfer to the cylinder liner and piston increases.
2.) Calibration trade-offs are required to reduce the NOx formation caused by high combustion temperatures.
3.) Calibration trade-offs are required to limit the maximum pressure rise rate in order to reduce engine noise.
Good engineering involves achieving optimal results while managing the trade-offs inherent in constraints. Our opposed-piston, two-stroke engine provides many levers that allow us to achieve the remarkable ISFC and BSFC results documented in our technical papers.
Gerhard Regner
Director, Applications Engineering
Achates Power
I’m a mechanical engineer with 3 years of experience in industry. A personal hobby of mine is to study internal combustion engines and how, why one is different than the other. This has led to me take an interest in working for engine companies, although now I find it a bit hard to get into one because of not having the advanced skills I see required (advanced CFD, CAE etc). I contemplate going to Master’s school to a place that has a dedicated engine research lab. Let’s hear it from you sir.. what skills do you think an engineer must have to get into a company like yours? What do you typically look for in candidates? Thanks for replying.
Congratulations on your new 2 stroke diesel.
I drive a two stroke diesel pickup all of the time. A 1960’s Jeep with a Cerlist 3 cylinder motor.
If you ever need to show the new with the old I have several of the trucks.
Or if you wish to repower one of the original Jeeps that came with a 2 stroke diesel I may have an extra I’d be willing to work with you on.
Daniel Horenberger
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