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Old 08-25-2008, 11:28 PM   #1 (permalink)
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Archimedes screw throttle

I may be blowing smoke on this one, but it occurred to me and I wanted to put it out there and find out the opinion of people much more knowledgeable. I have read that one of the things that limits engine efficiency at less than wide-open-throttle positions is the lack of efficiency of air moving past the throttle (plate, body? I don't remember the word for it for sure, just the thing that throttles the air intake). It occurred to me that something like an arhimedes screw whose rotation could be completely unhindered or even augmented via an electric motor for wide open throttle might be more efficient if you had to slow it down, ie hinder its rotation for less open throttle. Just free wheeling or with electric motor augmentation, I would think it would lose much less energy than the standard-type throttle. Any thoughts? I admit to having much less knowledge than some, but I am not going to stop thinking for myself just because of that, even if I occasionally look like an idiot. For all I know, this type of throttle has been implemented before or someone attempted to implement it before.

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Old 08-25-2008, 11:42 PM   #2 (permalink)
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A restriction is a restriction no matter what form it takes.
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Old 08-26-2008, 08:05 AM   #3 (permalink)
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I think Frank's right, it's just a different (more complicated and expensive) method to achieve the same result. With a single screw in a pipe it isn't even a positive-displacement device, so you would have air bleed (drawing air through the passage) and would not be able to super-charge. A twin-screw Lysholm supercharger would be able to be slowed down as a restriction or sped up to provide positive pressure, but the control system to do this as a primary engine speed control device would be VERY complicated (not to mention the safety aspects of a motor-driven device as the motor speed control?).

The best system I have heard of yet was BMW's Valvetronic, where electronic valve lift control was the "throttle" limiting the amount of air allowed into the cylinders. This was better because it kept port flow velocities high and allowed better mixing of the air and fuel at light engine loads.
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Old 08-26-2008, 03:07 PM   #4 (permalink)
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Quote:
Originally Posted by Frank Lee View Post
A restriction is a restriction no matter what form it takes.
Sorry, but that is like saying that, dragwise, a car is a car no matter what form it takes. If you have some actual data to support the idea that the air flowing over a partially closed plate and through a tube has less turbulence than the air flowing through a freewheeling or motor-augmented archimedean screw, then fine, but just putting forth such an oversimplification without justification is pointless.
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Old 08-26-2008, 03:20 PM   #5 (permalink)
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There are ways around the airbleed problem. I was just putting forth an idea, with the notion of discussing its efficacy if properly implemented, not discussing what would have to be done to properly implement it or the difficulties in implementing it. I am not trying to be offensive, I was just asking for an evaluation of the concept and perhaps further discussion, if necessary, of ways of improving upon the idea-assuming it has any validity at all. I'm just saying don't be so quick to throw out the bathwater because it is a little dirty unless you are certain there is no baby.
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Old 08-26-2008, 03:33 PM   #6 (permalink)
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I think it is an intriguing idea myself. you have a pressure drop there with the throttle, it would be nice to put it to use
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Old 08-26-2008, 06:20 PM   #7 (permalink)
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Quote:
Originally Posted by ronarprfct View Post
Sorry, but that is like saying that, dragwise, a car is a car no matter what form it takes. If you have some actual data to support the idea that the air flowing over a partially closed plate and through a tube has less turbulence than the air flowing through a freewheeling or motor-augmented archimedean screw, then fine, but just putting forth such an oversimplification without justification is pointless.
No, it isn't.

Think of the point of the throttle... think of the meaning of the word "throttle". It is to restrict. It is to prevent a runaway engine; to regulate engine rpm and power.

Why is intake turbulence a problem?
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Old 08-26-2008, 06:26 PM   #8 (permalink)
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That's no oversimplication. A pressure drop is a pressure drop. Kinda like "HHO is a Scam" isn't an oversimplification. It's the truth.

Now, if you use a turbine to capture the energy of that pressure drop, then you'd be onto something.

Turbulance schmurbulance. That's why the "tornado" air intake dohickey we all remembered works so well. A third year mechanical engineering student learns that it doesn't take much to disrupt laminar flow. You don't have to induce turbulance - it's already there, I promise.
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Old 08-26-2008, 06:29 PM   #9 (permalink)
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I think Ron misread your post Frank. Ron, I think you misread Franks post

Frank just said a restriction is a restriction is a restriction.

I take that to mean that cylinder doesn't care as long as the mix is right. It could be a roots type restriction or a throttle plate. Throttle plate has been done Something else is going to take some head scratching, but if there is a bolt on for existing gas cars that can help close the efficiency gap with diesels, then it's definitely worth discussing.
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Old 08-26-2008, 06:41 PM   #10 (permalink)
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You guys should check out the honda r18 engine. Its drive by wire and under load load conditions it switches to a delayed intake valve timing. In this mode the throttle is opened much farther and gains of up to 16% were seen by minimizing pumping losses.

Only easy way to do it is drive by wire though

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