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exhaust driven supercharger

exhaust driven supercharger
  [vote for,

yes i know a turbo is the same thing or idea for the most part. but a supercharger draws power from the engine to create power. what if the turbine side of a turbo had a shaft that conected to a pulley instead of a compressor and the belt lead to the supercharger obviously. that would definitly make it more efficent like a turbo. how would it compare in performance to a regular turbo? since the compressor would be about the closest you could get it to the motor. have they maybe already thought of this and tried it? i'd like to know.
nate200dhc, Sep 09 2003

Description of a supercharger http://www.automoti...ysuperchargers.html
I have no idea what the text of this idea is trying to say, but maybe this will help clarify matters for nate200dhc
[pluterday, Oct 17 2004]


       It's been done. A British diesel, the Napier Deltic T1837K used them. Since a 2-stroke requires a positive air flow to scavenge and hense start, they connected the turbo to the drive train to get air moving when the engine spins. The engine drives the turbo until about 1/3 engine power, then the turbo begins to drive the engine above that. the engine mentioned above is a piece of crap in many other ways, but the turbo design was good. I haven't seen it anywhere else but then there's not many 2-strokes being made any more.
Entropy, Sep 09 2003

       is this pulley driven by the motor? if it is then you just described a centrifical supercharger.they are smaller than the roots type and fit in most engine compartments.   

       other wise by adding a belt into the system adds it's own mechanical inefficentcies.
ih_smvdta, Oct 01 2003

       Greetings from Holland! this is a very interesting forum. Stumbled on it purely by coincidence. Two stroke engines -when fitted with superhargers- do indeed use gear driven ones. Expelling of exhaust gas from the cylinder, filling it with a new mixture and compressing it all needs to be done in virtually one stroke since the other stroke is the explosion- and power stroke. Therefore a mixture-filling under pressure will speed up the expelling of exhaust gases (and is indeed partly used for that purpose besides providing a richer and compressed mix) and driving a turbine by means of exhaust gas would be a serious hindrance for a speedy exhaust process. That's why gear driven compressors are chosen for two-strokes. The Roots-type goes very well with a two stroke engine, since it is a real compressor even at low rpm and its gear drive makes it run proportional to the engine rpm, so there's an almost ideal pressurisation from idle to full rpm. Large two-stroke diesels are indeed abandoned since the 70's (as Entropy rightly says), but that's largely because they do not meet modern emission standards anymore. Therefore GM did not continue the 567-645-710-line, but now focuses on its four-stroke H-engines; some of which are capable of 6000 hp. Two-strokes were mostly popular because of their simplicity and low maintenance needs (as long as their rpm is below 1000) and the Deltic design was rather an exception to that. They ran at 1500 rpm and their design was very sharply calculated, so they ran into cooling and metallurgy problems, just like the early Wankel engines. And they were two-stroke because it would have taken someone like Rubik to get the valve mechanisms right. Other than that I consider the Deltic to be a brilliant and highly efficient design. As for superchargers: I had a Kreidler Florett moped, which in Holland are only allowed 49 cc cylinders; otherwise they are considered as motorbikes and require a driver's license (which is ashame since the design could manage 125 cc cylinders and there even were water cooled race versions). Because of that design reserve (without exceeding 49 cc) I fitted it with a battery and an electric blower, made with a car vac fan and a Mabuchi 540 electric race car motor (the ones who are radio controlled). It eventually worked and made the moped go 70 mph instead of the usual 40, but at a unhealthy fuel consumption rate and an enormous amount of time until it finally worked moderately well. The carburettor's venturi aperture and its fuel nozzle gauge are a finely tuned combination together with the right sort of expansion exhaust system and a pressurised filling system immediately upsets this balance, which has to be found anew with trail and error. To correctly adapt the fan's rpm to a specific engine-rpm was the biggest headache, since the enhanced airflow often drew too much petrol from the fuel nozzle which flooded the engine. And that's only with a flimsy moped. I doubt if a Kirby vac would do the trick on bigger engines. Turbos on Formula 1 cars operate at 50,000 to 100,000 rpm and produce a staggering 3 bars (sorry, I was raised metric and 1 psi is approx 0.07 bar and I was awful at maths so be my guest), which is huge for a mere centrifugal system, which is inherently "leaky as hell". Since a very good vac with multistage fans can produce a vacuum or overpressure of 0,2 bar (and the Kirby is only single stage with approx 16.000 rpm), I hope you see my point. Still, hope flows eternal.   

       Best regards to all forum members!   

       Gerhard Schreurs
gerhard, Oct 10 2003

       I think what you are trying to do is power a supercharger by way of a turbine. Technically this is still a turbocharger. What you are doing is changing the compressor that you use. Instead of having an axial compressor connected directly to the turbine you want to route the power to some other sort of compressor located near the engine intake. I've toyed with this idea a good bit because there are other compressor types that are more efficient than the axial compressors used in turbos. Most notably there is the Lysholm screw which has higher adiabatic efficiency, resulting in lower output temperatures, which is great for forced induction engines. The difficulty is this. You have to reduce the speed a LOT and transmit the power mechanically. That means a pretty extensive set of pulleys and such. Difficult to design and also heavy. Turbos have enough trouble spinning up as it is. If they have to accellerate the mass of a whole lot of pullies and such, I think the lag would be pretty awful. All things considered I think you could do it, but it would take a lot of work and you might lose any gains just due to the inefficiency of the transmission system.   

LymanSS, Nov 21 2003

       As ih_smvdata very fairly said, this is a very well known type of supercharger, called "Centrifugal Supercharger". It is actually one of the three type of Superchargers (Roots type, Centrifugal type, Lysholm or twin-screw type). You can find many of them on the eBay for prices of 200 - 2000 $ (Powerdyne, Procharger, Paxton, Vortech, Turbonetics, etc).   

tzoutzoukos, Apr 17 2004

       It should be noted that a turbo also draws power from the engine, albeit indirectly. This is due to the fact that the hot exhaust gas has to do additional work to exit the exhaust, over a normally aspirated engine. This causes an increased back pressure in the exhaust manifold, which in turn saps some horsepower from the engine as it has to work harder to push out exhaust gases. Naturally, this effect is masked out by the increased power once the turbo reaches optimum RPM.   

       Perhaps more efficient would be a Turbo that is spun up by mechanical drive, whilst closed off from the exhaust, then dropped into the exhaust flow when at speed.
volvoman, Aug 26 2004

       for one a belt driven supercharger is powered from the engine. just use the turbocharger because if you drive the belt from the exhaust it would waste energy by having them unconnected. u just waste energy by having them on a single axle.
#1gknus, Jul 17 2007


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