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05-25-2002, 06:40 PM | #1 |
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Some Subaru ideas to improve low-RPM boost
I came across two interesting FHI (Subaru) patents that both seek to provide good boost at low RPMs without sacrificing turbocharger efficiency at the high RPMs.
The first you can read in full in US patent 4,730,457. This describes a system that utilizes a cranshaft-driven supercharger for low-RPM boost in series with an exhaust-driven turbocharger for the higher RPMs. Sounds like the old Lancia rally car from the '80s. The second is a Japanese patent, 63-201319. It describes a turbocharger which consists of two turbochargers (one small, one large) in a single housing. Since I don't read Japanese, the only thing of interest within the patent are the diagrams attached below. Is this great news, or what? Probably not, because both of these patents are from the '80s. But who knows? Maybe the B4 RSK two-stage turbo system has merely been a platform to work out the switchover kinks and pave the way for the supercharger/turbocharger system that Subaru really wants to build.
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05-25-2002, 09:34 PM | #2 |
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Hmm,
Turbo+super, you must be referring to the Group B Lancia Delta S4. A real monster. Bit of trivia, this beast was also Lancia's first AWD rally platform. The second one is intriguing. It's also a bit confusing. If you look at the two upper drawings, Figure 3 seems to show the turbine side of the dual turbo assembly. The direction of the waste gas would indicate that the smaller left turbine spins counterclockwise. The larger right turbine would seem to spin clockwise. Ok, no problem there. But if you look at Figure 2, which appears to be the compressor side there is a problem. Since it's the compressor side, it simply must be the other side of the turbo so the view is simply a left-right reflection. This appears to be correct based on the relationship between the two circles. Now the larger compressor is spinning counterclockwise as you look at it. Ok, it's pumping air out to the left and to the throttle body. The smaller compressor would then be spinning clockwise and apparently pumping the air the wrong way as oriented to the outlet pipe. This is only a problem, I think, if the two bearing center sections are in the same plane. If you offset one relative to the other, then you can take the clockwise pump off the smaller compressor off the bottom and join it to the output from the larger wheel. Other than that, looks pretty conventional with the wastegate and all. The parts 12A and 12B would be the large turbo and the parts 13A and 13B would be the small turbo. I'd be curious to know the control strategy for the butterfly valve 11A. Wilkey |
05-25-2002, 09:42 PM | #3 |
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Cool post, Jon. Thanks. Sorry I have nothing to contribute.
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05-25-2002, 09:53 PM | #4 |
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I have this on my car already, WTLW
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05-25-2002, 11:48 PM | #5 |
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There was a LOT of work done in the 40's on aircraft supercharging that looks like the former. The big radial engines had turbocharger,supercharger combinations, as does the Detroit Diesel engines. The concept is to get basic supercharging from the crank driven one, then up the pressure with the turbo unit with a little higher efficiency.
The japanese also did a lot with the turbo spool up "problem" in the 80's (one of the papers you saw). They tried a lot of different approaches, with smaller dual turbos being the preferred method. Also, ceramic turbines, wild turbine blade designs, variable inlet geometries (moving vanes like the M1 tank), other exotic metals, etc, etc. There was also a practical limit to the reduction in size due to bearing friction, which is one reason we have only one turbo for a 4 cyl engine (the other being cost for a second turbine). There are ways to decrease spool up RPM for a turbocharger, but, they are either complicated or loose efficiency at higher RPM (or cost too much). Turbines like to be run at a constant speed. We can do things for better flow but this only gets us so far. If you really want power at lower RPM, the only real way to get it is to go with a supercharger (or bigger engine :-). Eaton has a nice design and is well proven. The WRX engine is designed to be boosted. A good match for those with more money. |
05-26-2002, 01:59 AM | #6 |
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I seem to recall an article in Road & Track that spoke of super/turbo aircraft engines....Probally about 2 months ago.
Mr. Jon [in CT]: You are the master of all technical posts! I have yet to read a post of yours that did not give me a headache and lots of info. Thanks for putting them up here! Grant |
05-26-2002, 11:05 AM | #7 |
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Portablvcb, yes a lot of very interesting piston engine ideas came out of WWII Aircraft, including water injection and the Supercharger/Turbocharger combination. At the peak of development, some of these engines such as the R-4360 had 28 cylinders, displacements of over 4000 cubic inches and horsepower of 3500-3800. They used a centrifugal supercharger that compressed the intake charge and several turbochargers that geared directly to the crankshaft. Pretty cool stuff for over 50 years ago!
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05-27-2002, 10:52 PM | #8 |
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Mark B.
Ok, now you did it. Now you will have to explain why a turbocharger was geared directly to the crank The prelude to the turbine engine was indeed the engines on the Bearcats and Super Constellations. The neat thing is that a lot of the real advances were not in the ideas themselves but in the material development necessary to be able to actually implement the ideas. For every thing done today you can see a pre-WWII example. Enough lecturing for these young kids. Charlie |
05-28-2002, 04:49 AM | #9 |
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The R-4360 radial aircraft engine displaced, approx. 4360 cubic inches, and used 4 rows of 7 cylinders. The 'turbo's' mentioned by Mark B. were called "PRT's". "Power recovery turbines" used exhaust gas velocity to spin these, shafted to the the rank to help reduce drag on it.
This engine was/is one of the most complex piston engines ever produced and used to power aircraft, the B-29 being the most notable. There were experimental 42 cyl. radial engines flown prior to the end of the war, however turbine(jet) engines precluded further development on these. |
05-28-2002, 08:56 AM | #10 |
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Here is the thing about patents.
First, a lot of ideas are patented but never fully developed, so the technology may not be complete or even scientifically sound. A lot of patented ideas are later abandoned for this reason. Also, any patent worth having will be challenged in court, and many patents fail because they fail to meet the strict standard that requires a truly innovative new idea rather than an idea based on a logical progression of existing non-patented technology. For example, the first patent you mentioned basically combines a supercharger and turbocharger. This is not a new idea and Subaru's patent would likely be tossed if it were challenged. The second patent seems to describe a twin turbo setup, but with the turbos being combined into one housing. This one might hold up, who knows... This thread is really interesting and my comments are not meant as a criticism, just an observation. Don't be too surprised if you don't see these ideas in production any time soon. |
05-28-2002, 09:07 AM | #11 |
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I neglected to mention Fuji Heavy's triple turbo patent (U.S. 6,112,523), which was awarded less than a year and a half ago. It's meant for use on high-altitude aircraft, but ...
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