Posted on 06/23/2015 12:50:20 PM PDT by Red Badger
New Zealand's Duke Engines has been busy developing and demonstrating excellent results with a bizarre axial engine prototype that completely does away with valves, while delivering excellent power and torque from an engine much smaller, lighter and simpler than the existing technology. We spoke with Duke co-founder John Garvey to find out how the Duke Axial Engine project is going.
The Duke Axial Engine is lighter, more compact and already slightly more powerful than a typical equivalent engine, even though this is just a prototype
Duke Engines' 3-liter, five cylinder test mule is already making a healthy 215 horsepower and 250 lb-ft of torque at 4,500rpm – slightly outperforming two conventional 3 liter reference engines that weigh nearly 20 percent more and are nearly three times as big for shipping purposes. With an innovative valveless ported design, the Duke engine appears to be on track to deliver superior performance, higher compression and increased efficiency in an extremely compact and lightweight package with far fewer moving parts than conventional engines.
The Duke engine is an axial design, meaning that its five cylinders encircle the drive shaft and run parallel with it. The pistons drive a star-shaped reciprocator, which nutates around the drive shaft, kind of like a spinning coin coming to rest on a table.
The reciprocator's center point is used to drive the central drive shaft, which rotates in the opposite direction to the reciprocator. "That counter-rotation keeps it in tidy balance," says Duke co-founder John Garvey. "If you lay your hand on it while it's running, you can barely detect any motion at all, it's quite remarkable."
That's borne out by the video below, where the engine revving doesn't even cause enough vibrations to tip a coin off its side.
Instead of cam- or pneumatically-operated intake and outlet valves, the cylinders rotate past intake and outlet ports in a stationary head ring. The spark plugs are also mounted in this stationary ring – the cylinders simply slide past each port or plug at the stage of the cycle it's needed for and move on. In this way, Duke eliminates all the complexity of valve operation and manages to run a five-cylinder engine with just three spark plugs and three fuel injectors.
The Duke engine ends up delivering as many power strokes per revolution as a six cylinder engine, but with huge weight savings and a vast reduction in the number of engine parts.
The engine has shown excellent resistance to pre-ignition (or detonation) – potentially because its cylinders tend to run cooler than comparable engines. Duke has run compression ratios as high as 14:1 with regular 91-octane gasoline. This suggests that further developments will pull even more power out of a given amount of fuel, increasing the overall efficiency of the unit.
Alternative fuels would appear to be a promising possibility. In a 2012 interview, Garvey said "we just switched it over [to kerosene jet fuel] one day and it just ran straight away, as well if not better than it was running on petrol."
Garvey tells Gizmag "we've developed the engine to the point where we feel it's ready to be commercialized. But we're still without funding, and we're looking for the right application to build toward. The engine seems suitable for a wide range of functions, but we need to find the right funding partner to develop it toward a niche that can maximize its advantages."
That's unlikely to be automotive in the immediate future; car manufacturers have already sunk a lot of money into their own engine technology. But aeronautics, portable generators and marine outboard motors are uniquely placed to take advantages of the Duke engine's high output, compact dimensions and low weight.
Another key opportunity might lie in range extender motors for plug-in hybrid vehicles – engines that don't drive the wheels, but run at high efficiency to drive generators and top up the battery of electric drive cars.
Duke has partnered with engine development company Mahle in the US, formerly Cosworth in the UK, and is ready to begin commercializing the technology once the right customer comes along.
"The estimate is that it's probably a process of a couple years to get it to production ready," says Garvey. "This has been a huge undertaking, and sometimes you wonder if you should have started in the first place – but we've built an engine with some impressive advantages over current technology. It's the smallest and lightest engine around for its displacement and power output.
"Even our prototypes are outperforming established engines of the same displacement and there's a lot of development left in there for further weight reduction and performance gains. So we're very optimistic."
The Duke Engine – Version 3
The Duke Engine features axially mounted pistons that drive a star-shaped reciprocator
More info:
http://www.dukeengines.com/
New Engine Technology Ping!...................
Sounds like a radial?
Axial. Pistons go back and forth in the axis...............
How is this concept different from the Wankel Engine?
Axial, not radial design...............
Ping
Watch the videos at the link for more detailed explanation..................
Swash plate — https://en.m.wikipedia.org/wiki/Swashplate
Inefficient at converting linear reciprocating to rotary motion.
No valve and ports — dirty on I burned hydrocarbons.
High compression — dirty on NOx.
Going nowhere..
I dunno ... 5 cylinders means it burns more gas than a 4-banger ...
bump
Yeah, that was my question, what are the emissions like.
Looks like many hydraulic pumps. Sounds to me like it has promise.
Make it a turbo Diesel and I’m in.
“How is this concept different from the Wankel Engine?”
1. It has pistons.
2. It has a ‘crankshaft’.
From Their website:
What about emissions?
Like the Wankel rotary our combustion chamber is unencumbered with valves and such like. However unlike the rotary we approach a near optimal chamber shape far closer to a conventional 4-stroke engine. Therefore we achieve a much more complete burn than a rotary.
Charge motion development will further improve our combustion efficiency to approach that of a conventional 4-stroke.
There is currently some oil required for the seals to work and this can add to the emissions, however our consumption is far less than that required for a 2-stroke or rotary.
From their Website:
How long would it take to develop a diesel powered Duke?
We know that the SI Duke engine runs on kerosene (JetA1) with few changes from an optimised petrol version. During our forth-coming test program we intend to try the engines on Diesel fuel as it is not greatly different (chemically speaking) from kerosene. We have high hopes that the Duke engine will become the the world’s first internal combustion engine to run on such a wide variety of fuels. Using spark ignition Duke engines with heavy fuels will result in much smaller and lighter engines than comparative compression ignition Diesel engines. We will release our test results as they become available.
From their website:
What fuel types can a Duke engine run on?
To date most of our development and testing has been on gasoline of various octane ratings. Other commonly used SI fuels such as biogas CNG, ethanol, methanol, lpg could be easily tuned for with no physical changes to the engine.
We have done some SI testing on JP8 (AKA Jet A1 and kerosene). Initial results are very encouraging and we plan to do some more optimisation here as we learn more about the Duke’s unique characteristics. We expect that JP5 will also be able to be used in Duke engines with few changes.
Performance and BMEP - 3 litre Duke Engine
Performance test status on gasoline:
Torque: 339 Nm / 250lbft @4500 rpm (lambda 0.9), safe map spark.
BMEP: 11.8 Bar / 171psi
Power: 160 kW / 215hp @4500 rpm (lambda 0.9), safe map spark.
Significance of current gasoline performance status:
11.8 Bar BMEP is competitive with conventional SI engines.
3.0L torque output of 339Nm / 250ft/lbs is above that typically achieved by comparable conventional engines - due to pistons reciprocating at 120% of output speed, allowing a 20% higher output to be achieved at any given speed.
160kW power output is competitive with conventional SI engines of equivalent displacement and is currently achieved at only 4500 rpm.
V3i gasoline performance reported is below its real potential due to the lower Jet A1 compression ratio used and interim precautionary limit of 4500 rpm in this test phase (design target 6000 rpm).
Performance test status on Jet A1:
Torque: 292Nm / 215lbft @3500 rpm (lambda 0.88) detonation detected spark advance – 5deg.
BMEP: 10.2 Bar / 148psi
Power: 126kW / 169hp @4500 rpm (lambda 0.88) safe map spark advance.
Significance of current Jet A1 performance status:
Torque on Jet A1 achieved between 79% and 100% of gasoline baseline between 2000 and 4500 rpm.
These Jet A1 full load test results are considered particularly encouraging. The 10.2 bar BMEP achieved on Jet A1 is marginally above that of a Lycoming O320E comparator at rated power, operating on AVGAS. This is above the BMEP considered feasible with Jet A1 in conventional naturally aspirated spark ignition engines.
V3i Performance on Jet A1 is expected to increase significantly from this initially encouraging level due to operating at higher speeds with further combustion system and calibration optimisation.
“Looks like many hydraulic pumps. Sounds to me like it has promise.”
Advantage: There are no valves.
Disadvantage: There are no valves.
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