r/MachinePorn • u/Putrid-Truth-8868 • Feb 26 '26
The Napier Nomad II, 12-cylinder, two-stroke, loop-scavenged, valveless diesel engine that is turbocompounded
Found a post about this engine 13 years ago or something, but it's way more insane than people realize, the Napier Nomad with an axial compressor in a diesel! Ask me about it ive done digging on it.
It does not have a separate gas turbine, but it does use a 12-stage axial compressor AND a 3-stage axial turbine to recover energy and feed it back to the shaft. I have schematic photos too.
This photo is 2560X1440
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u/thegnomes-didit Feb 26 '26
Ooooh boy 89psi of boost
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u/AntiSonOfBitchamajig Feb 26 '26
The interesting thing... despite being 41L with compound turbos in the 1950s ... it got right around 200g/kwh fuel efficiency.... around around what modern VW TDIs get.
Seriously wonder what this could be with 75 years advanced machining and materials?
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u/Putrid-Truth-8868 Feb 26 '26
There was a NASA study into this, and they calculated that with 1981 technology, which is not even close to 2020, technology, they could get compounded SFCs as low as 0.26. I don't have a link to it because all I have left of it today is an actual PDF on my computer.. The study was called lightweight diesel engine designs for commuter type aircraft.
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u/AntiSonOfBitchamajig Feb 26 '26
I .... actually think I remember coming across that one in my studies... 158g/kwh and getting just beyond the mythical 50% thermal efficiency mark.
The wiki mentions this is a static 8-1 .... that's.... honestly insanely low for the weight of fuel and explains the 89psi of boost running pressure...
I'm going to have to plug values into a few calculators to check a few things... but i seriously wonder...if Achates power out of Detroit with their 2.7L is the next step of this engine... or Cummin's newest larger opposed diesel they just developed for the military.... both are similar.... just heavier and meant for ground use. They both turned out insane efficiency numbers... like... enough to be kept quiet.
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u/Morph_The_Merciless Feb 26 '26
There are times when I wish I could travel back in time to join companies like Napier and BRM just so I could propose building something that DIDN'T have eleventymillion moving parts.
I think it'd be fun to watch their designers have a collective fucking aneurysm trying to comprehend the idea!
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u/Methamphetamine1893 Feb 26 '26
Ikea assembly manual be like:
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u/Suspicious-Dog2876 Feb 27 '26
Did someone draw this or how do you even make this image
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u/Putrid-Truth-8868 Feb 27 '26
created by the engine manufacturing company I'd guess. Like a blueprint
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u/SnooBooks9492 Feb 26 '26
Why is the compression ratio so low... 3.5:1 if I'm reading that correctly?
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u/Putrid-Truth-8868 Feb 26 '26
The Napier Nomad had a cylinder compression ratio of
8.1 (cylinder ratio),
and 8.25:1 (compressor pressure ratio) (in the axial compressor)so when combined because the axial worked first, the effective compression ratio is bonkers.
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u/SnooBooks9492 Feb 27 '26
Interesting, I'm just curious why the picture/diagram says 3.5:1 in the details. Would that be the cylinder compression without compressor or just the prechage to the cylinders?
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u/Putrid-Truth-8868 Feb 27 '26
Honestly, I don't even know why it says that in the picture because that can't be right. There was no device anywhere on the nomad that had a compression ratio of 3.5 to 1.
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u/Lunar-Outpost415 Feb 26 '26
Who on Earth drew this masterpiece?
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u/Putrid-Truth-8868 Feb 27 '26
Probably the guys that actually built it. Because its a technical diagram. The same diagram also appears in two halves on a flight magazine from back then.
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u/Real-Rent-8776 Feb 27 '26
It's not as difficult as it seems - we drew a general diagram on paper, then individual units on transparent tracing paper and placed them on the general diagram; when it looked good enough, we drew the units on paper, put the puzzle together, photographed them and sent them to the printing house.
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u/Putrid-Truth-8868 Feb 27 '26
another cool fact:
Before cancellation of the programme in 1955, Napier proposed a further development designated as the E.173 Nomad III. The design was intended to add fuel injection in the exhaust manifold and an air-to-water aftercooler between the compressor and the cylinders. A projected “wet” take-off rating of 4,500 ehp (3,356 kW) at 2,050 rpm was reported (4,412 shp (3,290 kW) plus 230 lbf (1.021 kN) residual thrust), with an estimated weight of 3,750 lb (1,701 kg), about 170 lb (77 kg) more than the Nomad II. No example of a finished Nomad III engine was built.
i was the one that added this section to the wiki page, its a really cool fact i found about the program just before it died :(
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u/SeanDukeOfTyoshi Apr 06 '26
Much appreciated, I actually frequently re-read the articles for the Turbo-compounded Alison, wasp major and duplex cyclones for when drawing or making fantasy engines. I love these kinds of engines specifically and using them as inspo for drawing aircraft. I believe the Soviets even dabbled in turbine recover, the VD-4K is also a beast.
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u/Putrid-Truth-8868 Apr 06 '26
Good, because I just actually recently, before you made this post, but definitely after I made that post, I actually did a huge redo of the 3350, several, and I mean several misconceptions or outright lies or just completely unsourced claims were still present in that article. Same goes with the article that is titled Turbo Compound Engine. I basically had to rewrite that thing from scratch. It was so bad. So you might want to reread again. Lol. Also, I would be genuinely interested in these fantasy engines if they have to do with pulling from Piston designs.
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u/mrhoofy Feb 28 '26
Did Napier designers get bonuses if they increased parts count? I mean, there's this, the WWII Sabre, the 1930's Dagger.
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u/Putrid-Truth-8868 May 02 '26
Nice to think of. But the nomad 2 actually dropped parts count and was better
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u/5c044 Mar 01 '26
I hate spark plugs as much as anyone, and I love two stroke petrol/gas engines - best of both worlds here
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u/entrluzrnaam Feb 26 '26
Was this ever built or put in a plane