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XyZspineZyX
08-05-2003, 07:22 AM
Does the 2 stage work?

In game, do they just kick in automatically?

Search just times out.

XyZspineZyX
08-05-2003, 07:22 AM
Does the 2 stage work?

In game, do they just kick in automatically?

Search just times out.

XyZspineZyX
08-05-2003, 07:56 AM
Apparently the Russians, "didn't need no stinkin' superchargers"



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XyZspineZyX
08-05-2003, 09:08 AM
LOL

Has this issue come up already?

Didn't see anything in the updates about this...

It's kinda like only having 1 nut...

Tully__
08-05-2003, 01:51 PM
To my knowledge, the P-47 has a two STAGE turbosupercharger, not a two SPEED supercharger. The turbocharger part of the deal has a widget that automatically maintains ground level manifold pressure up to over 20,000 feet (~6000m). While pilots may have had the means to mess with turbo governing in flight, it's not modelled and would work differently to the two speed arrangement anyway.

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Salut
Tully

XyZspineZyX
08-05-2003, 02:33 PM
Turbos are great, you don't have to mess with the bost controls, and they make the best boost under high engine load, while mechanical superchargers rely on high RPM--and you have to remember to shift them.

Does anyone have any technical info on turbocharger installations in WWII? I doubt they had fancy modern stuff like ceramics and VATN, but did they have wastegates and ball bearings? One often reads of the US's "Turbos for Bombers" policy, because tungsten was a strategic material. Was the W used as a construction material or an alloy?

XyZspineZyX
08-05-2003, 03:19 PM
JR_Greenhorn wrote:
- Turbos are great, you don't have to mess with the
- bost controls, and they make the best boost under
- high engine load, while mechanical superchargers
- rely on high RPM--and you have to remember to shift
- them.
-
- Does anyone have any technical info on turbocharger
- installations in WWII? I doubt they had fancy
- modern stuff like ceramics and VATN, but did they
- have wastegates and ball bearings? One often reads
- of the US's "Turbos for Bombers" policy, because
- tungsten was a strategic material. Was the W used
- as a construction material or an alloy?

Ball bearings? Well, they'd have to, wouldn't they? Try getting something to spin at 18,000 rpm or whatever the P47 turbo did without... I'm not too keen on embarking on that project personally! /i/smilies/16x16_smiley-wink.gif The 8th Airforce certainly gave the ball bearing plants of Germany a whole lot of attention they probably wouldn't have minded doing without.

The P47 turbocharger had a wastegate to regulate the pressure/RPM. I don't have the POH at hand, but IIRC you had to pay a bit of attention to the charger RPM. I remember being rather disappointed with the FB implementation.

I think it is safe to assume that the turbines were fixed-geometry and did not have ceramic blades back then. /i/smilies/16x16_smiley-happy.gif

Turbos have their advantages, but certainly significant drawbacks as well. All that ducting being one, that turbine and associated problems another. And as I was saying, I don't think the pilots could leave them alone to that degree, although I will have to check. I'd be interested in finding figures on the efficiency of turbo- vs. superchargers.

Cheers,
Fred

No sig as of now, as people apparently can't handle reality without creating too much trouble for the poor mods.

XyZspineZyX
08-05-2003, 03:40 PM
JR_Greenhorn wrote:

-
- Does anyone have any technical info on turbocharger
- installations in WWII?
-----------------------------------------------------

Look here : http://rwebs.net/avhistory/opsman/geturbo/geturbo.htm

XyZspineZyX
08-05-2003, 04:21 PM
effte wrote:
- Ball bearings? Well, they'd have to, wouldn't they?
- Try getting something to spin at 18,000 rpm or
- whatever the P47 turbo did without... I'm not too
- keen on embarking on that project personally! The 8th
- Airforce certainly gave the ball bearing plants of
- Germany a whole lot of attention they probably wouldn't
- have minded doing without.

Thanks for the reply.

They wouldn't neccessarily have to have ball bearings. Most turbos use high pressure oil to feed the bearings, and I assume this was always the case. They could have used plain, roller, or needle bearings with sufficient oil pressure (& low enough speeds), or even tapered roller bearings to control thrust of the spool. I think the bearings in a turbo are some of those parts that are just ingored until they give troubles.

It is my understanding that the famous ball bearing plant targets were producers of generic ball bearings for all manner of applications. Turbos usually require dedicated or specific bearings, do they not?

effte wrote:
- The P47 turbocharger had a wastegate to regulate the
- pressure/RPM. I don't have the POH at hand, but IIRC
- you had to pay a bit of attention to the charger RPM.

Do you mean pressure/ engine or turbine RPM?
POH=? (Sorry...)

Was 18,000 RPM a guess or did they really spin that slow in those days?
I was amazed at how slow the Jumo 004's & such of the Me 262 spin. Only like 8000 RPM or something. Here's a thought, how about moving some air through there? Then maybe they wouldn't overheat! (I know, the metalurgy wasn't up to snuff yet)

XyZspineZyX
08-05-2003, 08:47 PM
So you guys are saying, um basically...yes, it does work...or wait your saying it doesn't work...I'm confused...

No, don't work.

Yeah without the charger it's kinda like having 1, hehe, ball bearing...



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XyZspineZyX
08-05-2003, 11:52 PM
TX_Heater wrote:
- So you guys are saying, um basically...yes, it does
- work...or wait your saying it doesn't work...I'm
- confused...

I'm mostly interested in how it worked.

XyZspineZyX
08-06-2003, 12:51 AM
http://rwebs.net/avhistory/images/_geturbo/ge_fig22.JPG</a>




Message Edited on 08/06/0312:10AM by JR_Greenhorn

XyZspineZyX
08-06-2003, 01:02 AM
To my understanding the P-47 had a two state turbo compression system.

The first stage was an exhaust gas driven Turbocharger, mounted under the tail. This was controlled by the exhaust gasses generated by the engine. If it's RPM got to high, the pilot opened the waste gates, to let excess exhaust out, and reduce the Turbo's speed. From what I understand, the Turbocharger only really came into effect in high altitude flight.

The second stage was a gear driven Supercharger. I understand that it only was a single speed supercharger, and did not require pilot attention.

Multiple gear speeds are only used on a Supercharer, for superchargers that are intended to give extra compression at high altitudes. The second gear speed is much faster than the first speed, and produces much higher air compression. However, if one uses that speed at to low an altitude, it over compresses the air, and can pop the supercharger like a balloon, or blow the compressor blades off, depending on which gives first.

In Il-2, the multi-speed Supercharger is modeled, as is the hand's off compression system. However, the P-47's system is neither of those; the Thunderbolt's turbocharger has an infinitely variable speed, pilot controlled, Turbocharger, with a single speed supercharger. To my understanding, this system was judged to complex (game engine wise) to model, just for a single aircraft, and the system itself was simple enough in real operation, that the hand's off compression system, used by the German aircraft engines was substituded instead.

You can tell the P-47's turbosupercharger system is actually operating in Il-2 by observing the manifold pressure for a given throttle setting as altitude increases. At full 100% throttle, the aircraft maintains a full 57 inches manifold pressure continuosly up to 9,000m. No other aircraft in the game, not even the German fighters, can maintain manifold pressure up to that altitude.

Note: German aircraft measure their manifold pressure in ATM, and Russian engines measure in torr. 1 atm = 29 inches = 760 torr. All they are measuring is the air pressure at the engine's air intake, after all of the intake compressors, such as turbo chargers, super chargers, and ram air, but before the engine air intake throttle. (That's the Throttle the pilto controls, by the way.)

For more information on engine operation, try these articals:
Pelican's Perch #15: Manifold Pressure Sucks! (http://www.avweb.com/news/columns/182081-1.html)
Pelican's Perch #16: Those Marvelous Props (http://www.avweb.com/news/columns/182082-1.html)
Pelican's Perch #18: Mixture Magic (http://www.avweb.com/news/columns/182084-1.html)
Pelican's Perch #19: Putting It All Together (http://www.avweb.com/news/columns/182085-1.html)
Pelican's Oerch #31: Those Fire-Breathing Turbos (Part 1) (http://www.avweb.com/news/columns/182102-1.html)

Harry Voyager

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Message Edited on 08/05/0307:05PM by HarryVoyager

XyZspineZyX
08-06-2003, 01:44 AM
great links --- those are the best explainations of those aspects of piston-engined aircraft that i've ever read! well written, easy to follow, but with enough substance to fully explain things in depth.
thanks!


HarryVoyager wrote:
- For more information on engine operation, try these
- articals:

XyZspineZyX
08-06-2003, 09:16 AM
JR_Greenhorn wrote:

- They wouldn't neccessarily have to have ball
- bearings. Most turbos use high pressure oil to feed
- the bearings, and I assume this was always the case.
- They could have used plain, roller, or needle
- bearings with sufficient oil pressure (& low enough
- speeds), or even tapered roller bearings to control
- thrust of the spool.

Ah, certainly. Didn't think you were talking about bearing types, but rather generic bearings. Had I read some of your later posts on engines first I probably would have guessed that you are not one to equate ball bearings with bearings in general, as many do. /i/smilies/16x16_smiley-happy.gif

The gas turbines (no turbochargers per se) I have had the opportunity to explore to that level of detail have generally had separate bearings for radial and axial loads. Some have a high-pressure oil film at the end of the shaft to take up the axial loads. No idea about what the specific design was back then.

- It is my understanding that the famous ball bearing
- plant targets were producers of generic ball
- bearings for all manner of applications. Turbos
- usually require dedicated or specific bearings, do
- they not?

I think they did them all. Bearings are bearings, after all. The process will be similar independent of type. Much easier to make them all in the same facilities, don't you think?

- effte wrote:
- Do you mean pressure/ engine or turbine RPM?
- POH=? (Sorry...)

Turbine RPM. And POH = Pilot's Operating Handbook. Aviation and TLAs, y'know... /i/smilies/16x16_smiley-wink.gif

- Was 18,000 RPM a guess or did they really spin that
- slow in those days?

It was a number I think I remember, albeit not with 100% certainty. Not all that surprisingly low IMO, no order of magnitude apart from modern gas turbines. A modern car turbo is a lot faster though, right? But also a lot smaller, nowhere near the same air volumes! How about truck turbos?

- I was amazed at how slow the Jumo 004's & such of
- the Me 262 spin. Only like 8000 RPM or something.

Hehe, yeah, that one is an eyebrow-raiser!

When flying season comes to an end and I find time to recommit myself to my little recip engine simulator project, I will definitely have to pester you with questions. Recips aren't given a lot of time in todays AE educations (for some peculiar reason /i/smilies/16x16_smiley-wink.gif ) so the finer details are sadly all new to me. Valve technology... yikes!

Cheers,
Fred


No sig as of now, as people apparently can't handle reality without creating too much trouble for the poor mods.

XyZspineZyX
08-06-2003, 12:15 PM
effte wrote:
- And POH = Pilot's Operating Handbook.
- Aviation and TLAs, y'know...
-
- When flying season comes to an end and I find time
- to recommit myself to my little recip engine
- simulator project, I will definitely have to pester
- you with questions. Recips aren't given a lot of
- time in todays AE educations (for some peculiar
- reason) so the finer details are sadly all new to me.
- Valve technology... yikes!
-
- Cheers,
- Fred


Acronyms: great if you already know what they mean, incomprehensible if you don't. http://ubbxforums.ubi.com/infopop/emoticons/icon_wink.gif
Sorry, but you lost me with TLA and AE--which I assume might possibly be Aerospace Engineering?

"recip engine simulator project?"

It sounds as if we are at opposite ends of the spectrum. I've been able to get a fair amount of experience with (non-aircraft) recipricating engines, but I've spent lots of time in library basements trying to learn about gas turbines. Unfortunately, there's not a lot of technical experience that way.

Valve technology is probably the most interesting aspect of 4-str0ke engines. Why does it scare you?

XyZspineZyX
08-06-2003, 03:29 PM
AE is indeed Aerospace Engineering. TLA means Three Letter Acronym. Hey... no, no, no! Don't throw that at me!

OUCH!

Guess I deserved that one. /i/smilies/16x16_smiley-wink.gif

Now, for the runner up price... what's an ETLA?



I had to look up that VATN thing though so we're even! /i/smilies/16x16_smiley-very-happy.gif

I've spent way too much time calculating my way through gas turbine engines... and most of a year fulltime creating a hi-fi simulation of two of them! Very interesting work! The recip thing is unpaid hobby work though, just for the hell of it.

Valves aren't scary. There just seems to be a lot to learn in that area, loads of ingenious solutions to various problems. As you said, interesting. But also something which I have to learn. I'm stuck in the Lycoming IO-540 era as far as recips go... /i/smilies/16x16_smiley-happy.gif

Cheers,
Fred

No sig as of now, as people apparently can't handle reality without creating too much trouble for the poor mods.

XyZspineZyX
08-06-2003, 10:40 PM
I'm going for Mechanical Engineering; I hope to get into engine design eventually. I've just gotten into aircraft in the last few years as a hobby. Someday I hope to get my pilot's licence and give flying a serious go, but I have neither the time nor the money right yet. For now, it'll just be cars & bikes & stuff like that.

I'll have to look up ETLA. I had used VATN without realizing it. Darn acronyms!

XyZspineZyX
08-07-2003, 07:19 AM
Extended Three Letter Acronym.

Time to start throwing things again! /i/smilies/16x16_smiley-very-happy.gif

In my line of work, I write technical aircraft instructions. I frequently find myself writing sentences containing only words like "the", "and", "it" and a bunch of acronyms! Horrible, really...

Cheers,
Fred

No sig as of now, as people apparently can't handle reality without creating too much trouble for the poor mods.