I’ve never found a definitive answer to “who invented turbo super-charging”. I’ve read that the American’s worked on it extensively in the mid-1920s (ie: Mt. Whitney tests) and then shelved it. (pending materials technology). Your post states that the Germans were the first to perfect it. Did they pick up from where the U.S. left off, or were they ahead all along?
hay trexx, I’m not really sure who invented either the supercharger or the turbocharger. It could have been an american. In the early 1900’s the US was advancing rapidly in the areas of manfacturing and new mechanical equiptment as was parts of europe (industrial revolution period). I never really looked into the history of the supercharger.
I know in the late 30’s and very early 40’s germany and later the reich was advancing by leaps and bounds in the areas of weapons and engineering development. Things like the electron microscope, tape recorder,Wankel engine, and interstate roadway were all first. One the military side things like automatic weapons, early RPG’s, mechine gun interrupters (WWI), Articulated tank suspension, finally ballistic missiles and later the space program came the the reich. you can go on and on.
The supercharger used by the luftwaffe was basically the same as the allies. The way they differ was how they controlled boost. The allied supercharger operate more effiency at very high alitiudes early on because of it’s 2 stage design (basically compressing the air and then compressing it again). The draw back was a larger heaiver unit that needed a intercooler due to the heat it created. To compersate for altitude changes it used 2 speeds a high and low. The problerm this is it gave it poor all altitude performance.
The blower used by the luftwaffe operated off a regulator that automatically controlled the boots pressure. This allowed boost to be near optimum at all alititudes and RPM’s. no peaks and valleys. In short 2 speeds could not cope with all altitude and engine RPM’s as well as a supercharger that was boost regulated. Couple this with high pressure fuel injection and you got one high performance aero engine in a small sleak package. Late in the war the luftwaffe used a larger superchager (The AS) this gave more boost volume and thus allowed the engine to operate at higher alttitudes. The luftwaffe never went to a 2 stage design, but they didn’t seem to need it.
I’m not sure I did a great job of explaining this, but in one of these tech manuals I have it give a good description of how both work. I’ll try to dig it up.
I once met one of the chief designers of the Allison V12 engine at a get together in a display up front in plant three. I do remember him saying that a lot of what he learned was just from knowledge that was already there. And in house at the old Allison Experimental Company. The company built aircraft engines (started out with the “Liberty Engine”) during WWI after designing and supplying engines for or sorts of customers including Rolls Royce. Between the wars they built race car engines of all sorts, and had one of the largest custom engine shops in the world. They were heavilly involved in supercharged engines between the wars and probably knew more about them than anybody else building engines. Most all were centrifical (or axle flow). But with a blower feeding the engine other problems soon showed their face. Some were not critical, but heat was. One must put himself back to the twenties and thirties to really make a grasp on this problem. The field of metalurgical engineering really wasn’t much at the time, and alloys were not really as vast as they were in say 1952. The good part is that aircraft engines actually run at a much slower rpm than an automobile engine, and are rather constant in rpm’s (to a certain extent). So the experimenting was kinda crude by today’s standards, but did work. I’ve seen boxes of two piece pistons similar to what was used in todays diesels (top piece is made of cast iron or steel and forged into an aluminum body). Alittle heavy, but not really noticed as much due to the lower rpms of the engine. What the Germans used I don’t know, but if you take a serious look at their engine designs you’ll notice that they really didn’t use turbos much on their aircooled engines till they had their backs to the wall. Where as the Allies could just swap out an engine for a new one most anytime they wanted to after 1942. Who invented the turbocharger I don’t know. But Allisons was playing with them in 1937 if not earlier. If it was in 1945 I could have asked Harry Miller (he’s the guy that Offenhauser copyed), as he was a friend of my Mom and Dad. I don’t think it was Mercedes or Autounion.
Allisons has probably built more superchargers than anybody on this planet, but really don’t think they ever did a turbocharger. I do know they were big on multi staged supercharging setups. Biggest I’ve ever seen was two turbos feeding each other for each bank of the engine, and then all that feeding two large Roots type blowers. The turbo V12’s were developed in the high altitude chambers at what was known then as plant two, and parts for those engines were still there 40 years later. We used to go over there and get cylinder head studs to make screw drivers out of as the steel was either 4140 or 4340 (I can’t remember), and once forged would last a couple lifetimes. The big differences in Allison V12’s is in the attached transmissions and induction systems. Otherwise they’re all pretty much generic. I suspect the samething for the Packard V12’s as well. That and like I said before there really was all that much interest at Allison to go further as gas turbines we known as the future in 1943. If the government had of asked them, they would have in a heart beat.
To touch on the radial engine a tiny bit again. There is actually two kinds of radial engines. One of them is the kind we all know of, and the other actually spins the cylinders (I still can’t figure out how that one worked). The latter one was used mostly during WWI.
gary
-
I maybe wrong, but I think they might have built BMW 801’s with a multistage blower setup. I’ll check it out later
-
The one field the Germans were the best at without a doubt was in metalurgy. They were the first to use stainless steels. Had the best heat treating operations on the planet. Their machining operations were actually similar to what we used at Allisons, but with one exception. They led the world in grinding technologies (and in some cases still do lead the world till this very day). I still remember examining a couple pairs of ball bearing that were built in Germany, and their counter parts built in America. They were beautifull! We’ve since past them in that field, but it took over thirty years to get it done! The Germans possessed the finest vien of coal used for heat treating metal in the world, and is still to this very day the best. Even with todays vacume furnaces; coal still gives the best heat. Liquid salt is the only thing close engough to compair with it, and the carbon from coal is still better.
gary
Squeakie said-
To touch on the radial engine a tiny bit again. There is actually two kinds of radial engines. One of them is the kind we all know of, and the other actually spins the cylinders (I still can’t figure out how that one worked). The latter one was used mostly during WWI.
I know about 1/100 as much about engines as you guys- here’s a little info on rotaries.
The rotary engine is actually a pretty simple affair, with basically one moving part- the crankcase/cylinder/propeller assembly. That all rotates at speed around a fixed crankshaft/rod/ piston assembly that is bolted to the firewall.
The engine aspirates fuel/ air mixture through the crankcase and then via transfer ports in the cylinder walls, or intake pipes externally run from the case to the head, depending on the design.
Some had one valve which also regulated air intake, some had two. Pushrods were actuated like in a radial engine, only the mechanics were reversed with the followers running around a fixed cam.
These things ran at full open all the time, with a fuel/ air gate regulating flow into the case, but it was set pretty much one way once the engine had been started, idled and then powered up- wide open.
Decsent and landing usually was achieved via intermittent ignition cutout.
The design solved the big problem of the day, excessive vibration because the entire engine was a giant flywheel. However it was unstable and could get away from an inexperienced pilot in a turn in the direction of engine rotation relative to forward movement.
Also, they drank gas because they were never on cruise, so were used exclusively in fighters.
But they ruled in max power output for quite a while. And I think were the first to go past 10 hours without overhaul.
the radial with the rotating crankcase was the early style. Later ones used a rotating crankshaft that was attached to the propeller in one way or another. Actually any water cooled engine will run longer than an air cooled engine in a similar situation. That’s just engineering and ridding the engine of heat (remember heat is the killer as well as power). If you build up too much heat in the heads and cylinders you kill the pistons and cylinder walls let alone burn up the valves. That heat also breaks down the oil to the point that it no longer is a viable lubricant. The engine oil is also a primary coolant in an internal cumbustion engine. I think the reason they drank so much gas was because they were of a much larger displacement and second have to run a rich fuel mixture to help cool the heads & valves. In similar displacement engines the water cooled engines ran off and hid from their air cooled counter parts. An example here is the B29 bomber and the experimental verson that had the W3240 engine in it. But better yet is the XB38 that simply was a B17E converted over to use standard Allison V1710’s. That one came close to happening as it did better in every catagory, but in the end it was determined that it would be best not to reconfigure the production lines.
gary
finally had the chance to check on the supercharged BMW 801 engines awhile ago. It appears that there wasn’t a multistaged supercharger used after all. But I did find that there were three planes built with turbochargers that they just couldn’t get to work right. So they were then reworked again (seems like they started out as A4’s and and a lot of internal work done to them due to a major change in the C/G) to something else with inline engines (may have been what the “C” models started out as). There were DB 603’s and DB605’s installed in them (not sure just what a 605 is right off hand). Project was later scrapped.
gary
If I understand it right, turbosupercharging is what we today call a turbocharger. It works off of exhaust gases. The draw back to this is long lag time, poor ability to maintain mainfold pressure at all engine RPMS, added duct work, and finally you are creating a restriction with the impeller in the exhaust flow. I think the luftwaffe dumped the turbosupercharger Idea for 2 reasons. one superchrgers were basically being perfected at about the same time and two, they always were looking tyo keep weight down while at the same time providing “power on demand” as they call it. I know the luftwaffe was well aware of 2 stage supercharging but felt it was unnesserary. Instead using better air/fuel control, supercharger control, and using lighter less complex methods like GM 1 and MW50 to keep there power plants small, light, yet very powerfull.
The luftwaffe messed around with both 2 stage superchragers and twin superchargers but nothing went operational. Kinda like the counter rotating prop something else they found unnesserary.
Stan, I don’t think the Germans or the Japanese ever perfected the turocharger well enough to use it in service. Only GE in the US was able to develop the power turbine (the part in the exhaust flow) part of the turbocharger well enough for that, and their expertise in that area helped a lot in US/British jet engine development. The supercharger has an efficiency drawback in parallel to the turbocharger’s losses due do increasing exhaust pressure, because it draws power from the crankshaft for it’s motive power and because it cannot extract heat energy from the exhaust flow. Maybe the Wright R-3350 in the Constellation and DC-7 had the greatest overall efficiency with turbo-compounding. They had the usual supercharger powered by the crankshaft and had three power turbines in the exhaust flow capturing heat energy and transferring it through gear trains back to the crankshaft.
There is an advantage that is unique to the turbocharger because it can bootstrap, which enables it to be more efficient at high altitude than the supercharger, allowing higher ceilings than the supercharger. At least that’s what my old brain remembers.
At the start of WWII turbochargers were a fairly new thing on the shelf, and most users were still learning. The first major problem they found was excessive heat being added to the pressurized air supply (as in very very hot). This lead to bearing failures and later impellers buring up befire the air even got into the cylinder heads. Most of this was solved with water jackets and a secondary lube system that had it’s on cooling system. Then there was the red hot charge of air that was buring pistons faster than they could make them. From there we see the evolution of intercoolers, and see the turbos being moved away from the engine is at all possible. (those long pressure tubes help to cool the charge). But it was doable as many countries used them. Later on waste gate systems and other pressure relief systems were developed to help rid the engines of “supercharger lag.”
When compairing the turbo to an axleflow supercharger you gotta take in the whole thing to see why one was in favor over the other. When a supercharger of one form or another is driven off the crank shaft or even hydraulicly it takes horsepower to drive it. The more pressure and CFM it develops the more horsepower it takes to drive the blower. With the volume of air that they needed for a large engine displacement I’d say your loosing at least a 150 hp if not over 200 hp. at the crankshaft. But with a turbocharger your actually using spent exhaust gases to drive the turbine wheel as well as the heat from these gases. It’s kind of free, but not without the above problems. It will restrict the exhaust output somewhat, but not enough to worry about once you’ve pressureized the chamber to a great extent (the chamber pressure will actually help push the exhaust gas out of the cylinder head). So in effect it’s way more efficient than a conventional blower. From what I can gather the Germans were trying out turbos from two different manufacturers, and running the pressure system locked down without a wastegate. The wastegate is used to keep the turbo pressure built up and also eleminating “lag.” On the otherhand you also have to remember that it was still kinda new for everybody (use in aircraft)
The MW50 water boost setup was used for two good reasons. First and probably foremost was to help fight detenation in the combustion chamber (water turning to steam seem to create a “cushioning effect” between the piston dome and the chamber roof). Plus the the steam when converted to dry steam in micro seconds has a faster expansion rate that the flame travel of the explosion in the cumbustion chamber. I doubt that the added alcohol had nearly as much effect as the higher compression ratios afforded by the water injection and vastly increased ignition lead.
But there’s another piece to this puzzle! The GM1 boost. Nothing more than nitrious oxide injection. This stuff is serious when it comes to making power, and has no lag or horsepower tax at the crankshaft. The drawback is that it’s really hard on the main bearings and piston domes due to detenation. Also the power span in time is greatly reduced to the amount of nitrious held in the container. A five minute supply would have been huge, and more than likely less than three minutes. I might be wrong but I also think it really dosn’t like extreme cold ambient temps (minus thirty and stuff like that). I’m surprised that the Germans didn’t also try a pure oxygen injection setup as this really makes tons of horsepower, but also can be dangerous.
gary
the supercharging system you are refering to is fairly common. They use small turbos to make them spin at a higher rpm and actually start being efficient at a lower rpm (engine). They then supercharge the axle flow blower which is pretty much shot by the time it has fifty hours on it. NiChrome steel for the turbine wheel would have helped to solve this problem as well as some of the 300 series stainless steels that were developed in the fifties, but would have been way too heavy. Plus this system probably took 500 horsepower to drive it. Axleflow superchargers like light weight turbine wheels unlike a more common roots type blower that will actually work with just about anything. The reason we always see them made of aluminum is that the rotors are a pain to machine and a soft alloy is easier. With todays metalurgy these systems could have been made to live many times longer. All in all that kind of a setup on an aircooled engine was a problem looking for a place to happen, and an engine repair shop’s dream come true. Still that system probably worked well at most all altitudes. Now we have multi-stage turbo chargers that do it all. But in aircraft they still are stop gap only to be replaced with a turboshaft gas turbine (not a true turboprop) like the TF56 and others. Always wondered why they quit working on the true turboprop engines back in the fifties as they are considered to be the most effecient engines developed for aircraft use.
gary
Thanks for that info jeanton, that explains alot. There was a ton of research and development behind making that system work. This would explain why the US didn’t want the P-38 in luftwaffe hands. I would have to agree with you. Since the US had no problems making that system work (and quite well by the P-38 altitude and speed). Then on the other hand it seems all the info I have on the luftwaffe turbosupercharger they complain about both power output problems and maintaince issues. I don’t think they every got it right. I also don’t see any documents that indcate they ever went any further than testing, much less even considered placeing a turbosupercharger system in service. I would believe they never really perfected it and that why it didn’t work for them. Another question I had answered.
I know they captured and flew at least 2 P-38’s. But have never seen anything about them reverse engineering that system. Odd becasue the P-51 and spitfires they got ahold of they torn them down, picked them apart, and flew the pips off of them. This info could also be lost.
Squeakie your now my go to guy for tech info on this stuff. Thanks for your input. A pilot or a aircraft engineer I am not, but I do learn quickly.
I posed that question to my resident expert- airspeed. Airlines want it and the challenge of getting a big prop plane to go over 500 knots makes the a/c big and noisy, with lots of vibration. A big plane like the Electra cruised at about 375 knots.
Wow - this is a hot thread. I have pretty resonable experience with automotive engines & forced induction, hence my interest.
Squeakie, you are more than correct about the material manufacturing quality & skill in the German metal industry. It would seem that in recent history their skill’s are pretty hard to beat - look no further than the Rheinmetall gun as fitted to the Abrams M1A1, M1A2 & various other MBTs, which originated where?
I wish you could have been with me about twenty years ago! I used to go over to Plant Two a couple times a week (this was the old Allison plant that did most of their experimental work brfore building Plant eight). We used to see crates of spare parts for engines, and all kinds of testing equipment. The test cells over their were unique. This also the plant where the very first totally U.S. designed jet engine was built. Later they built test cells accross the street in Plant Three, and most of them are still there, but used for storage mostly. The way there were built pretty much made them bomb proof in the way they built the blast ducts. Walls are four to six feet thick! But they did manage to blow three of them up once killing five guys. They had a V12 engine that was a “cut away mockup”. Plus a couple others that were under tarps. I think the V12 we used to keep up front is the one over at Wright Patterson as it looks just like it right down to the paint job on the engine stand. They probably have the “cut away” too. Thinking back I kinda wonder what happened to the WWII and later jet engines that were on display. They had a TF56 cut away that was driven by an electric motor that was really neat as well as a TF41 and some others.
gary
gary
I suspect that Rock Island could have built one as well. I think that design came about with the joint effort between the U.S. and Germany. But with Rhinemetal tooled up to make the cannon you could also save a lot of money. Still keep in mind that there are other ideas on the drawing boards right now that can and maybe will replace that 120mm gun. A hint would be that cars are not the only things on the drawing boards that use a hybrid electric drive.
gary
there was a prototype airliner built that used a true turbo prop that had a eight or ten bladed prop mounted in front of a jet engine ( a true turbo prop). We did the engines, and it looked like a Boeing airframe (been twenty years ago). The props looked kinda funny looking and were not strait, but a compound curve).
gary
Thanks for encapsulating the situation and events well, Jon Eaton!
I’ve been under the impression that America did lead with turbo supercharging. It wasn’t folly or baseless caution to treat the technology special. Limey’s didn’t get to zing around on their own with the latest high altitude interceptor, the P-38 Lightning, unless they were nuetered. (the airplanes, that is… He, he, he…)
GE was assigned development of turbo supercharging because of their experience with hydro turbines used to produce electricity.
Sanford Moss experimented with turbo supercharging after World War One. He concluded sometime around 1925 that new materials would have to be created to continue development.
Apparently his work was taken up in earnest once suitable materials came into being…
I’ve often viewed this late war photograph that shows a convoluted exhaust gas piping and all sorts of gizmos and thought, “they’ve not quite figured it out yet”…
Blohm Voss 155