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I appologize in advance for any spelling errors.
here we go
First things first, some backround explanation. A Lysholm or screw type supercharger uses two intermeshing screws to force air into an engine, also the nature of the screws turning compresses the air it is pushing.
As far as I've
been able to tell the screws form a pocket that forces the air along as they turn.
My idea is to make a long set of intermeshing screws which have a varied pitch along their length.
At the intake end the pitch would be set so as to make large pockets of mixed air and fuel. As the pockets are forced towards the center of the screws the pitch would gradually change to make smaller pockets and increase the pressure. The pitch of the screws would change again at the middle and the size of the air pockets would grow back to their originall size or larger. Now If you were to ignite the air fuel mix in the pockets after they passed the smallest portion of the screw the increased pressure of the air in the pockets should cause the screws to turn.
All of which should in theory give you a small working turbine engine.
Unfortunately Most everything I know about screw type superchargers has been found online over the last few days. So I don't know if this is in fact a possible way to abuse them.
but as far as ideas go I think it's pretty neat.
Twin-screw type supercharger
http://en.wikipedia...sholm_superchargers
[BJS, Apr 27 2007]
(???) StarRotor
www.StarRotor.com
The name is descriptive enough. You'll see. [elhigh, May 07 2007]
(?) The StarRotor engine
http://starrotor.com/Engine.htm
...uses the Braton cycle [BJS, May 08 2007]
(?) StarRotor
http://www.popsci.c...4eecbccdrcrd/3.html
@POPSCI.COM [BJS, May 08 2007]
[link]
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Maybe you could just use two of them or more in opposite directions, instead of a specially made one. And inject the fuel in at the ignition point, instead of mixing it in at the beginning. |
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What do you think this engine could be used for if it works? |
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I think the main advantage is that it would be very small. My logic behind this is that the existing superchargers are much smaller than the engines that they are attached to but they still move the same volume of air. So if you could burn the same amount of gas in one then you would be creating the same amount of energy as in a much larger engine. The only thing I don't know for sure is if the screw design would be as efficient at harnessing the energy as a piston. |
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Also the reason I think it should be a moddified set of screws and not two sepparate sets is the same as my reasoning for mixing the fuel at the intake end. It would eliminate a lot of extra parts. |
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As for what it could be used for, well at the time I found it I was trying to come up with a way to make a turbine engine to power a moped. I found several articles about turning turbochargers into turbineengines, and while searching turbocharger types I got sidetracked onto superchargers. Which eventually led to this. |
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Turbine engines are relatively slow to react to throttle changes, which is why they are rarely used in land vehicles. I don't see how this would be any better. |
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Instead of only changing the rpm of the turbine I'm working on a plan to use an infinately variable transmission. That should help balance out the relatively slow reaction time of the turbine. |
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the transmission is inspired by my dads lawn mower, which uses one. It has a large flywheel turned by the engine, a smaller wheel makes contact with the flywheel at a right angle to it, moving the shifter changes the distance of the small wheel from the center of the flywheel to its outer edge which of course changes the "gear" ratio. |
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I have pondered this too - modding an off the shelf turbo with a DC generator as a small propane powered generator for campers, or as the generator stage in a serial hybrid vehicle. |
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However //existing superchargers are much smaller than the engines that they are attached to but they still move the same volume of air. So if you could burn the same amount of gas in one then you would be creating the same amount of energy// is almost certainly wrong. Existing superchargers aren't designed to burn fuel in them, or to extract energy from it. |
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[Afterblast], I checked up on these, and they are positive displacement. However, I cannot get it straight in my head how they could have a varying screw pitch and positive displacement at the same time, with varying volumes of positive displacement as well! Not that I think it won't work: it's just difficult to visualise, so I have no idea one way or the other. |
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I read that the advantage of the lysholm compressor is that the compression is done inside the lobes, before discharging, as opposed to pumping a volume of air into the discharge chamber and using the discharge chamber to form the compression. Pretty neat. |
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If your idea works, apart from the material problems which could be sorted out, the compression ratio needs to be higher than the normal design of about 2 bar. Anyway, +. |
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This idea is essentially baked as the StarRotor, an engine design that is effectively two superchargers working in concert, with a combustion chamber between them. That removes the actual combustion zone completely out of the realm of all the moving parts. |
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It's really neat in concept, and has been mentioned here before. See the link. |
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I like it, with or without BJS's modification. Except the part on wikipedia about being expensive due to close tolerances. Friction and leakage are my main worries. |
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As a compromise between two separate twin-screws and a single pair, you could have the compression screw on the same shaft as the expansion screw, with just a small unthreaded area in between. The unthreaded area wouldn't contact the cylinder wall, so it would be easier to put spark plugs there. |
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This is essentially what Wankel did when he invented his rotary engine, which was based on a supercharger design. I'm not sure how you're going to deliver the fuel and spark without a separate combustion chamber, though. |
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