Originally posted by: Saga
Originally posted by: Demon-Xanth
It's actually a twisted roots.
http://www.eaton.com/EatonCom/...chargers/TVS/index.htm
With a whipple the sides are different shapes.
http://www.whipplesupercharger.../content.asp?PageID=67
Out of curiosity, is it functionally any different?
Also, was this sort of a rip off of Whipple to not have to pay royalty fees, or did someone else come up with it first?
It's not the same at all.
The helical twist is an improvement in roots style blower efficiency by attempting to keep the rotors overlapped as much as possible so there isn't a gap. If the rotors were perfectly straight, there would be a open gap running the length of the entire rotor housing between atmospheric air and compressed air just after a set of lobes pass each other but before the next set of lobes came together. What makes roots blowers inefficient is that they don't actually compress the air. A roots blower works like a fan in that the intake air is compressed by layering it in the lower intake faster than the engine can consume it. The blower rotors and lower intake are not sealed by any means, so at a certain high enough boost vs rotor rpm, there is nothing stopping already compressed air from trying to depressurize back into the rotor housing and being recirculated and re compressed, thus heating the same air over and over again. Twisting the rotors helps with this a little bit by keeping the rotors overlapped as much as possible and minimizing gap exposure between atmospheric and compressed air.
A twin screw blower actually compresses the air in between the screws themselves. In a screw blower the screw shaped rotors actually come together close enough to trap air (rather than just act like fan blades like roots style rotors). The screws are tapered so the volume decreases axially as the pockets of air trapped between them move along from intake to discharge. The compression ratio inside the blower screws is always greater than the boost in the manifold, thus the pressure at the discharge port is always higher than that of the manifold (no recirculation), promoting one way flow and higher efficiency. Naturally the machining precision required for this is far far more complex and more expensive than a roots blower (air tight almost/barely touching metal spinning up to 20,000 RPM).
Coincidentally, each revolution of the screws past the discharge port results in a "pop" as the compressed air trapped between the rotors decompresses into the intake manifold. This pop occurring 10,000-20,000 times per second with the screw revolutions is what generates the characteristic whine of a twin screw blower.
Facebook
Twitter