If you could go back to WW-2 with the knowledge you have now in engine design...what would you improve? No jets...

[AbitNutz]

I would start with some smart but but not too radical ideas, because lets face it, they won't do too radical an idea. For example. Implement 4-valve heads and combustion chamber design on radial engines the way it should be done. As I understand it, the way the valves were laid out on the Bristol engines did not take full advantage of them the way they do today. My Harley M8 makes stupid power in comparison to my older but exactly the same CID twin cam and really, the only difference is that 4-valve head.

I would also go after the more efficient forms of turbocharging we use today, impeller designs, inter-coolers, etc. A lot of this stuff is really a matter of knowing to send your milling this a way instead of that a way. Yes, I know that's a silly simplification but today's turbos could easily be made in 1941 on a Bridgeport milling machine. In fact, today's custom turbo impellers are made on 1941 Bridgeport milling machines.

So how about a smaller displacement 18-cylinder radial of say about 1850 cid designed with 21st century knowledge of bearing material, intake, flow, turbocharger, combustion design and efficiency that was built on 1940's machinery. I think you could get something along the lines of 3000 reliable horsepower. Probably greater reliability than they had in the 40's.

I guess the idea is, could an engineer from now, go back to then, and with just his smarts put into production the common ideas of today's engine design, and heavily tweak their existing hardware and make some incredible improvements?

Yeah, I know, it would probably be easier to go visit Frank Whittle in his shed and point out a few things but I find propeller engines far more interesting.

 

[Capt. Vick]

Well since I have little to no engine design knowledge I say put me on the axis side and I will set them back a decade or more.

 

[MiTasol]

Give Allison in 1941 the centrifugal compressor technology they developed in the 1990s giving the later variants of the 250C series turboshaft engines a pressure ratio of 9.2:1 from a single stage compressor - that engine has the equivalent of a manifold pressure of 135psi.
This would give a smaller supercharger that would put all the two stage superchargers to shame.
Add fuel injection of the latest continuous flow variety to ensure even mixture distribution and hey presto.
The manifold pressure would still have to remain at WW2 levels without major redesign of the rest of the engine but the far more efficient supercharger and would provide far more hp at the propeller.

 

[AbitNutz]

Give Allison in 1941 the centrifugal compressor technology they developed in the 1990s giving the later variants of the 250C series turboshaft engines a pressure ratio of 9.2:1 from a single stage compressor - that engine has the equivalent of a manifold pressure of 135psi.
This would give a smaller supercharger that would put all the two stage superchargers to shame.
Add fuel injection of the latest continuous flow variety to ensure even mixture distribution and hey presto.
The manifold pressure would still have to remain at WW2 levels without major redesign of the rest of the engine but the far more efficient supercharger and would provide far more hp at the propeller.

That's what I'm talking about. All of a sudden you're a miracle worker Scotty.

 

[AbitNutz]

Well since I have little to no engine design knowledge I say put me on the axis side and I will set them back a decade or more.

Well, ok but when you guys lose it's gonna hurt.

 

[XBe02Drvr]

I guess the idea is, could an engineer from now, go back to then, and with just his smarts put into production the common ideas of today's engine design, and heavily tweak their existing hardware and make some incredible improvements

Can your engineer from now take his Cray supercomputer with him?? Does your time machine have that large a transit chamber? A lot of the super efficient technologies like the compressor that was mentioned are achieved with fluid dynamics calculations that aren't practical on a slide rule and require materials (cerametallics, etc) that weren't possible with available technology of the time.
The simple concept stuff like four valves/cylinder could surely be worked out, but the big jumps in fluid efficiency require more than just a concept to achieve any significant gains; likewise any significant gains in structural weight reduction from accurate detailed vibration and resonance analysis.
Cheers,
Wes

 

[Sid327]

The Ford developed V12 should have gone into production.

I think it showed greater promise than either the Merlin or the Allison, but for politics.


Reducing CID albeit with more modern tech will certainly gain you more hp and usable rpm through efficiency, but it loses you torque which is arguably more important.

 

[swampyankee]

God, not overvaluing torque again.

All high-powered aircraft engines are will have reduction gearboxes. If there are X horsepower coming out of an engine provided to a prop at Y rpm, the torque is the same. That low-rpm, high torque engine will be heavier. One may want a longer stroke, as increasing stroke may reduce sfc, which is why many engines designed for efficiency are under-square, but propellers turn power into thrust; they don't turn torque in thrust. Not once when designing and analyzing props and helicopter rotors, did I hear engine torque spoken of except when designing gears.

 

[Sid327]

God, not overvaluing torque again.
All high-powered aircraft engines are will have reduction gearboxes. If there are X horsepower coming out of an engine provided to a prop at Y rpm, the torque is the same. That low-rpm, high torque engine will be heavier. One may want a longer stroke, as increasing stroke may reduce sfc, which is why many engines designed for efficiency are under-square, but propellers turn power into thrust; they don't turn torque in thrust. Not once when designing and analyzing props and helicopter rotors, did I hear engine torque spoken of except when designing gears.

Nice, friendly reaction. Thank you.

Having more torque means making more hp at a lower rpm, which means more power to the prop. It also provides better throttle response.
Reduction gearing in a piston engine is in a pretty narrow band, unlike a helicopter where gearing is reduced from >30,000rpm down to around 300, so has little relevance as a discussion point. Using a a later model PT6 as an example, it gives around 1500shp but barely 230ft/lbs of torque at the output shaft before any gearing or torque multiplier is connected. Whereas a large capacity piston engine will be making ten times that at less than 1000rpm.

As I understand it an engine making better average torque can also swing a bigger and heavier prop with less power loss.

 

[XBe02Drvr]

propellers turn power into thrust; they don't turn torque in thrust.

Having more torque means making more hp at a lower rpm, which means more power to the prop.

Semantics, semantics! Sounds like a collision between engineerthink and operatorthink.
Power is work accomplished in a unit of time, usually a second. If you maintain a constant torque, but spin the shaft faster, you make more power. Likewise, if you hold RPM constant and increase torque (like any engine with a constant speed prop), you also make more power. It takes two to tango. I've watched all four engines in a P3 go from 1200 HP to 4800 HP in about four seconds with no change in RPM (but a huge change in airspeed and altitude!).
Cheers,
Wes

 

[wuzak]

There are other factors at play.

A high torque/low rpm engine will require heavier/stronger gear reduction than a low torque/high rpm engine of the same power output.

The caveat is when the reduction ratio is so large that multiple stages are required.

 

[wuzak]

The Ford developed V12 should have gone into production.

I think it showed greater promise than either the Merlin or the Allison, but for politics.

The promise the Merlin and Allison had was being in production at the time they were required.

 

[MIflyer]

1. Improve atomization of fuel. The science of aerosols was just getting started then. This really became a noticeable problem with the Whittle engine but all engines could have be benefited from improvements of that type.

2. Ask everyone why not use a liquid cooled inter/aftercooler. That was the real secret of the success of the two stage supercharged Merlin but no one else seemed to have a clue.

 

[swampyankee]

The promise the Merlin and Allison had was being in production at the time they were required.

Ford could likely get their V-12 into production quicker than Packard could do so with the Merlin

 

[Shortround6]

Ford could likely get their V-12 into production quicker than Packard could do so with the Merlin

Not a chance on god's green earth.

Ford would have to design the engine from scratch, get it to pass some sort of type test (even a relaxed one like the Packard Merlin) and once the design was finalized, set up for production.

Ford did not start work on the design of the V-12 until after they had seen both the plans/blueprints of the Merlin and a pattern engine.

See Ford built V-1650's?

for an old discussion on this subject.

 

[MIflyer]

The US Ford Motors Company DID build the Merlin!

They copied it using the plans they had been provided and produced a tank engine based on it. RR did as well, the Meteor engine, although it was traded to the Rover company in return for the Whittle Jet Engine division.

 

[Shortround6]

No they did not. The Ford engines used double overhead camshaft instead of single overhead cam. The Fords used a slightly pent roof combustion chamber.
Just because 2 engines use the same bore and stoke, and have the same number of cylinders doesn't mean they are the same engine.
The Chevy Z-28 302 engine and The Ford 302 both used the same bore x stroke and were 90 degree V-8s. Now try to claim one was copied from the other or that you can actually interchange any parts

 

[swampyankee]

The Ford V-12 was designed because they didn't like the Merlin, and they thought they could do better. To produce the tank V-8, Ford used as much of their V-1650 as practical, including the block and 60 degree bank angle

 

[Ivan1GFP]

Turbo-Compound engines.....

 

[swampyankee]

Working two-strokes, although getting a decent sfc would need fuel injection