Duke Engines' compact, lightweight valveless axial engine • Hacker News Board

Re: Duke Engines' compact, lightweight valveless axial engine

#21

Post by iaw » Wed, Nov 05, 2014, 9:52 PM UTC

noir_lord wrote: post #15

vlucas wrote: post #9

The money quote, for the TL;DR crowd: "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 su…

215hp out of a 3 litre is shockingly low except for a naturally aspirated carburator engine from the 80's. For example the 2 litre 2015 Mondeo Turbodiesel gets 210bhp. The article is interesting but reads like a marketing release, the weight saving is the interesting take away I think if reliability matches a modern diesel.

I do agree with you but a turbo diesel isn't a valid comparison because it is:

1) turbo charged 2) diesel fueled

An inter-cooled turbocharger setup on this engine would likely net an additional 100 HP without much issue (presuming the sealing issues aren't horrific). Generally 100 HP per litre of displacement is the gold standard for naturally aspirated engines (see Ferrari).

Re: Duke Engines' compact, lightweight valveless axial engine

#22

Post by Sophistifunk » Wed, Nov 05, 2014, 9:58 PM UTC

IanDrake wrote: post #16

MattBearman wrote: post #13

Earlier quoted context omitted.

As an RX8 owner (and enthusiast), I can tell you Wankel Rotaries aren't categorically better, or worse. They have strengths and weaknesses: - The vast majority of rotaries will need a full rebuild before 100k - worse - They rev to 10,000 RPM with an unbelievably smooth power delivery - better - I'm lucky to see 22 mpg - worse - The engine is so small and light that the RX8 has perfect 50/50 weight distribution - bett…

Learned stick on my second gen RX-7... -Almost no torque at low rpm - worse -Easy to flood, then once flooded major work - worse -Feed it a quart of oil every 1,000 miles - worse

We have a bunch of old rotary race cars in the showroom at the 9-5, you wouldn't believe how much noise and oil they put out the back whenever they need to be moved around :)

wank-wank-wank-wank-BANG!-wank-wank-wank-wank

Re: Duke Engines' compact, lightweight valveless axial engine

#23

Post by BrandonMarc » Wed, Nov 05, 2014, 9:59 PM UTC

I assume the application most people have in mind is cars. As others have said, electric seems to be the future there, so while this may be a revolutionary engine, it's possible the timing won't help it.

What about other applications? Would this work well for marine, aviation, factory, or other purposes?

Re: Duke Engines' compact, lightweight valveless axial engine

#24

Post by BrandonMarc » Wed, Nov 05, 2014, 10:11 PM UTC

iaw wrote: post #21

noir_lord wrote: post #15

Earlier quoted context omitted.

215hp out of a 3 litre is shockingly low except for a naturally aspirated carburator engine from the 80's. For example the 2 litre 2015 Mondeo Turbodiesel gets 210bhp. The article is interesting but reads like a marketing release, the weight saving is the interesting take away I think if reliability matches a modern diesel.

I do agree with you but a turbo diesel isn't a valid comparison because it is: 1) turbo charged 2) diesel fueled An inter-cooled turbocharger setup on this engine would likely net an additional 100 HP without much issue (presuming the sealing issues aren't horrific). Generally 100 HP per litre of displacement is the gold standard for naturally aspirated engines (see Ferrari).

Curious: what's the alternative to naturally aspirated engines? Space-bound rockets?

Re: Duke Engines' compact, lightweight valveless axial engine

#25

Post by erik_landerholm » Wed, Nov 05, 2014, 10:16 PM UTC

"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."

Seems convenient to use a pretty lame reference engine to make yourself look good. 3 liter engines have made near 1000HP for years now.

Re: Duke Engines' compact, lightweight valveless axial engine

#26

Post by Gracana » Wed, Nov 05, 2014, 10:17 PM UTC

BrandonMarc wrote: post #24

iaw wrote: post #21

Earlier quoted context omitted.

I do agree with you but a turbo diesel isn't a valid comparison because it is: 1) turbo charged 2) diesel fueled An inter-cooled turbocharger setup on this engine would likely net an additional 100 HP without much issue (presuming the sealing issues aren't horrific). Generally 100 HP per litre of displacement is the gold standard for naturally aspirated engines (see Ferrari).

Curious: what's the alternative to naturally aspirated engines? Space-bound rockets?

The other side of the coin is forced induction, using a turbocharger or a supercharger or even both. "Natural aspiration" just refers to engine with intake air at atmospheric pressure.

Re: Duke Engines' compact, lightweight valveless axial engine

#27

Post by JoeAltmaier » Wed, Nov 05, 2014, 10:24 PM UTC

erik_landerholm wrote: post #25

"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." Seems convenient to use a pretty lame reference engine to make yourself look good. 3 liter engines have made near 1000HP for years no…

How about hp per pound? Isn't that the advantage of this thing?

Re: Duke Engines' compact, lightweight valveless axial engine

#28

Post by mikeytown2 » Wed, Nov 05, 2014, 10:28 PM UTC

erik_landerholm wrote: post #25

"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." Seems convenient to use a pretty lame reference engine to make yourself look good. 3 liter engines have made near 1000HP for years no…

The best naturally aspirated piston engine is 166 hp per liter. The best naturally aspirated Pistonless rotary engine is 188 hp per liter [1]. The Duke is at 71 hp per liter; it has a long ways to go but it's already better than a naturally aspirated Diesel engine (44 hp per liter).

[1] http://en.wikipedia.org/wiki/List_of_automotive_superlatives...

Re: Duke Engines' compact, lightweight valveless axial engine

#29

Post by phkahler » Wed, Nov 05, 2014, 10:33 PM UTC

IanDrake wrote: post #17

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. 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.

One downside to that is that cooling everything will add to NOx in the emissions. A nice hot exhaust is needed for the catalyst to complete clean combustion. Not that it's a bad idea, just that it has an emissions tradeoff.

Re: Duke Engines' compact, lightweight valveless axial engine

#30

Post by phkahler » Wed, Nov 05, 2014, 10:39 PM UTC

MattBearman wrote: post #13

BrandonMarc wrote: post #7

Earlier quoted context omitted.

Thank you. I'd wondered how this would compare to a rotary engine. It's interesting how enthusiastic the rotary-engine crowd is, since my takeaway was always "well if it's so much better why isn't it more common".

As an RX8 owner (and enthusiast), I can tell you Wankel Rotaries aren't categorically better, or worse. They have strengths and weaknesses: - The vast majority of rotaries will need a full rebuild before 100k - worse - They rev to 10,000 RPM with an unbelievably smooth power delivery - better - I'm lucky to see 22 mpg - worse - The engine is so small and light that the RX8 has perfect 50/50 weight distribution - bett…

You missed one - perfect balance. The CG of a properly designed rotary does not move. It's the reason it can rev so high. And flat torque across most of the RPM range is the reason for the power density since torque*speed=power you increase power by spinning faster. Oh wait, you did say smooth power delivery. It does go together with the others.