This isn't a new engine, it isn't a new idea, and it isn't a particularly good idea.<p>Duke Engines have been around since 1993, and built their first prototype in 1996[1]. Axial engines themselves date back to 1911; Their practical use is limited to torpedoes, where the cylindrical form-factor is an advantage.<p>Axial engines have inherently high reciprocating mass compared to conventional piston engines, which is a catastrophic flaw in a performance engine design. Higher reciprocating mass increases inertia (reducing throttle response) and increases the forces at the end of the stroke (reducing maximum RPM). They offer no meaningful advantages in terms of fuel efficiency, and are likely to be less efficient in many applications due to the difficulty of implementing existing efficiency technologies (VVT&L, valve deactivation etc)<p>Both the current Duke engine and their hypothesised next-generation engine offers poorer specific power than current naturally-aspirated designs. The cylindrical form-factor is more difficult to package than a traditional piston engine; Camshafts offer enormous flexibility in terms of layout, allowing the engine to be squeezed into a multitude of shapes and sizes. Axial engines are inherently balanced, but balance is practically a non-issue in modern engines, even for layouts with very poor inherent balance.<p>[1]<a href="http://www.dukeengines.com/technology/overview/" rel="nofollow">http://www.dukeengines.com/technology/overview/</a>
No mention of meeting fuel economy and emissions requirements. Both of those are big topics that engine builders have to consider, with the 35mpg fleet-wide average that cars sold in the US must meet in about a decade. Having grown up in an age filled with car exhaust from carburated engines, I don't miss it a bit -- I <i>like</i> having clean air.<p>One of the comments to the article mentioned the difficulty in keeping high-pressure seals working. It was in conjunction with Wankel rotary engines, which have always had problems with the rotor tip seals leaking (ask any Mazda RX owner...) This engine has the same problem on the intake/exhaust end, as the piston carrier rotates past the openings.
Axial engines go back a long way, to at least 1917.<p><a href="https://en.wikipedia.org/wiki/Axial_engine" rel="nofollow">https://en.wikipedia.org/wiki/Axial_engine</a><p>That format is widely used in hydraulic systems, and is the basis of continuously-variable hydraulic transmissions. Classically, it has problems at high RPMs, but is well behaved at low ones.<p>It's an idea that might be worth looking at again. With better materials and controls, it might work. The geometry is more flexible than with Wankel engines. The elegant Wankel geometry means there aren't many parameters that can be adjusted to improve combustion. In a piston engine, you can design piston face geometry, cylinder head geometry and fuel and air injection points for better combustion. With a Wankel, you're kind of stuck with the geometry. We'll have to see how this new approach works on pollution control.
The only ICE advancement that really seems interesting to me is adding an extra cycle to inject distilled water into the cylinder for an extra power stroke.<p>The idea being that the heat from the prior explosive power stroke is used to turn the water into steam. Now you're using wasted heat energy and removing the need for cooling components.
"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."<p>Seems convenient to use a pretty lame reference engine to make yourself look good. 3 liter engines have made near 1000HP for years now.
The money quote, for the TL;DR crowd:<p>"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."
It seems to share some things in common with the rotary, like moving the ignition chamber past the fuel/exhaust ports, rather than opening/closing valves. So it will need some way to seal the cylinder during compression/ignition... will those seals tend to break up at 100,000 miles like a rotary's apex seals?
I assume the application most people have in mind is cars. As others have said, electric <i>seems</i> to be the future there, so while this may be a revolutionary engine, it's possible the timing won't help it.<p>What about other applications? Would this work well for marine, aviation, factory, or other purposes?
Looks interesting, but I'm guessing there is a lot of stress on the recipricator mechanism that the pushrods connect to, pushing against an incline to cause the output shaft to rotate.