But they also had engine driven superchargers.
The premise is to do away with the engine driven supercharger and use an exhaust driven supercharger instead.
Pratt vs Wright
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But they also had engine driven superchargers.
The premise is to do away with the engine driven supercharger and use an exhaust driven supercharger instead.
Or how about the German solution, an engine driven supercharger driven via a hydraulic coupling?
Oh ok. I re-read the earlier posts and I see what he means now. Thank you
It WAS done in the earliest radials which had low power mixing fans. But once you have that apparatus integrated into your engine, and the marketing folks are screaming "More power!", and the airframe designers are screaming "Less weight!", the temptation to gain some "free horsepower" by building more boost into your mixing fan/supercharger becomes irresistible. The farther down that road you go, the more horsepower you "invest" in your supercharger to gain more output at the propshaft. "There ain't no free lunch."
An impellerless large radial could probably be developed by using a tuned length induction manifold like the "bundle of snakes" you see on race car engines sometimes, but how are you going to stuff all that under the cowling and still get adequate cooling air to the cylinders?
Good point. Turbocharging was pretty much an infant technology at the start of WWII, and progressed rapidly during the war, but was still limited by the available metallurgy. The heat was the problem. I've got thousands of hours (as does most any professional pilot today) in planes with turbines made of alloys not achievable in WWII. Looking back, it's easy to ask "Why so?", but it's because technology is mainly an evolutionary process, not a train of brilliant quantum leaps.
Good call! While some of what you envision might have been achievable with tremendous effort and radical thinking, it would have been nigh impossible to sell that much technical risk to program managers obsessed with maximum output at minimum cost in the shortest timeframe.
Cheers,
Wes
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swampyankee
Chief Master Sergeant
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One of NASA's projects in the late 1970s was advanced general aviation engines (note that none were ever produced 
); one was a 5-cylinder, two-stroke diesel with a turbocharger (but no other scavenge blower) see https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19800013851.pdf
); one was a 5-cylinder, two-stroke diesel with a turbocharger (but no other scavenge blower) see https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19800013851.pdfShortround6
Major General
You need not only a good fuel/air mixture, you need the same amount of air (and fuel) to all cylinders. If your fuel injection was smart enough (which non electronic/computer fuel injection isn't) you can have the correct mixture in each cylinder but if cylinder #5 is only getting 90% of the air that cylinder # 1 is you have problem. Uneven power impulses acting on the crankshaft. This can lead to vibration problems much worse than a simple 10% loss in efficiency. This might be able to be solved with the snake pit of intake pipes referred to by
X XBe02Drvr . You need about the same length intake pipe or route from the supercharger to each intake port. You also can't squash things too much as you are going to reduce velocity/mass flow with each bend.
It is possible now, it was not possible then. during WW II and for a few years after NOBODY got more than 4.0:1 compression from a single stage compressor in service (lab may be different) even the early post war centrifugal turbo jets didn't go over 4 to 1. The GE turbos weren't even hitting 3 to 1 for most of the war. Please note that is referring to just the compressor section. How you drive it is a separate issue.
That and materials. Yes we have both better material and better (much better) processes now. GE was facing a problem with mass production of turbine blades early in the war. It was suggested that they switch to a material used to make dentures at the time. It had the strength, heat resistance and more importantly, the ability to make fast precision castings so they could eliminate much of the machining they were doing on each blade.
You can pretty much forget that notion, These were guys who were thinking on the edge. Unfortunately they sometimes pushed thing too far and got slapped up the side of the head. See
Wright R-2160 Tornado - Wikipedia
The article doesn't begin to describe what complicated engine this was
The 42 cylinders were made up of three 14 cylinder modules whose crankshafts were not connected. Instead they were geared (though shafts) to 7 lay shafts (one between each bank of cylinders) shown in green in the drawing to get the power to the front of the engine for the propeller gear box and to the rear for the auxiliaries. Wright sank about 6.5 million dollars into this project before giving up and going back to the "traditional" R-3350 Double Cyclone that powered the B-29. There were other unconventional engines. None really worked, perhaps with modern computer power their problems could have been solved but at the time they could not.
You won't. An engine using even 5lbs of boost (40in MAP) is going to have about 33% more power in the cylinders than an equivalent non supercharged engine, The supercharger isn't very heavy, and low boost at low altitude doesn't really take that much power.
it was because they weren't using 10% of the power simply for mixture distribution. They were improving the power to weight ratio and increasing altitude performance. This really shows up when you try to compare an late 20s or 1930 unsupercharged engine to a mid to late 30s supercharged engine and you are looking at power at sy 7,000 to 10,000ft. The unsupercharged engine could have lost 20-22% of it's power by 10,000ft. You loose about 2% per 1,000ft. Even a moderately supercharged engine with a peak power at 6-7,000ft comes out ahead of the more powerful sea level engine. Using more boost did start to suck up power fairly quickly but the engine could usually make more power in the cylinders than it could really stand up to. That is to say you could jam more fuel/air into the cylinder per minute than you could either effectively cool or the mechanical parts could take the strain.
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kitplane01
Airman 1st Class
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I think I've been educated. What clears the issue for me most is that apparently no one new how to make a compresses that did better than 4:1. If it's not possible, that's why they didn't do it.
Elvis
Chief Master Sergeant
Comparing the R-1820 to the R-1830, I've heard the Wright engine is a rougher running unit, but is an overall lighter weight engine.
The R-1830 tends to like running at a higher rpm and I believe max rpm is rater higher on that engine, as well.
swampyankee
Chief Master Sergeant
- 4,022
- Jun 25, 2013
It's still a mechanical drive, so it's really no different than a geared drive, possibly worse as the losses in the hydraulic coupling are greater. There was, of course, the opportunity for better matching than a fixed gear ratio provided
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Barrett
Senior Airman
Most of my antique-warbird experience was with Wrights, notably the 1820 in the Dauntless. My impression (based on interviews & reading) is that the Dee-troit auto makers had trouble meeting aviation industry standards for quite awhile, hence the impression of "externally lubricated" Wrights. ("What's wrong with the B-17? Only four things!")
FWIW, what I called the "Wright wrattle" was audibly distinct from the Patented Pratt Purr.
FWIW, what I called the "Wright wrattle" was audibly distinct from the Patented Pratt Purr.
Seems like the only Detroit plant making R-1820s was that of Studebaker; the only other Wright engine not made by Wright was the R-3350 produced by Chrysler. Problems with R-3350 were IIRC of Wright's making.
Studebaker-produced engines (-65s, -97s) ended up in B-17s, but seems like USN was no recipient of the Studebaker's engines, since there were no even numbers listed in the table. Wright was not licensing their engines production as widely as the P&W did.
Detroit was just fine in making aero engines, contrary to the Wright branch plant at Lockland that was a subject of Truman committee due to thing that would've seen people sent in Siberia had that was ongoing in Soviet Union. The Lockland affair was probably second to the torpedo scandal in US military history of 1940s.
interesting link
fastmongrel
1st Sergeant
Interesting read and all too depressingly similar to what went on at Boeing recently.
Parmigiano
Senior Airman
long time no see...
Just a curiosity: what was actually the ratio of boost between the built-in mechanical supercharger and the turbocharger in a P47 R2800 or in a B17/B24 engine?
I mean, were the two chargers really working 'in series' both creating boost or was the mechanical blower after the carburettor working mainly just as a pressure equalizer?
Just a curiosity: what was actually the ratio of boost between the built-in mechanical supercharger and the turbocharger in a P47 R2800 or in a B17/B24 engine?
I mean, were the two chargers really working 'in series' both creating boost or was the mechanical blower after the carburettor working mainly just as a pressure equalizer?
Shortround6
Major General
It depends on the power level wanted or authorised. The engine driven supercharger provided most if not all of the "boost" on the early P-47s. The turbo was responsible for making sure the Carb on the engine driven supercharger was getting sea level air pressure at the altitudes above sea level. Early P-47 used 52in of manifold pressure from sea level to around 25,000ft.
Low alittidue the turbo provided no pressure and at 25,000ft it was compressing the air over 2 to 1 before it reached the carb.
See> P-47 Performance Tests
Later as WEP power levels and water injection were added they used to turbo to boost the pressure going into the carb above sea level pressure and the engine supercharge multiplied the change.
Low alittidue the turbo provided no pressure and at 25,000ft it was compressing the air over 2 to 1 before it reached the carb.
See> P-47 Performance Tests
Later as WEP power levels and water injection were added they used to turbo to boost the pressure going into the carb above sea level pressure and the engine supercharge multiplied the change.
Admiral Beez
Major
Isn't "turbo" more of a marketing thing, a play off turbine?
I had a boom box stereo with something called turbo bass. Then there's turbo razors.
I've always read turbo charger means exhaust driven, super charger means belt or gear driven.
Admiral Beez
Major
On the P-38 Lightning and P-47 Thunderbolt, two aircraft built around their superchargers, AIUI they're turbine driven off of air flow. These were called turbo superchargers.
My old mech school instructors used to say: "If it's turbine driven, it's a TURBO charger! Leave the super out of it. He lives inside the engine and does a SUPER job at what he does.
We had an airfreight feeder operator back in the day that flew UPS, DHL, and Airborne parcels in a fleet of invasion striped DC3s, one Wright and three Pratts. One of the Pratts was grounded waiting for a reman engine, and they had a timed-out 1820 sitting around on its QECA mount waiting to go out, so just for grins and on their own time the mechs hung it on the empty firewall and ran them both up. The resulting clatter got the owner up from the dinner table with his mouth full of turkey, and was heard downtown, several miles away. One of the mechs told me that at certain RPMs the whole plane shook like a wet dog and the wingtips were rocking up and down a foot.
What is it they say about oil and water?
Cheers,
Wes
P-39 Expert
Non-Expert
Washing machine Charlie.
