Quote:
Originally Posted by ronarprfct
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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The Archimedes screw is like a grain auger.Archimedes designed his to pump out bilges on ships.Both require horsepower.They are also open on both ends.It would be difficult to achieve "idle" with an open pipe,albeit with a complicated pipe as you propose.Rotating the helix would not perform any "valving",which is what the butterfly valve does.The Archimedes screw also would provide a pathway requiring continuous acceleration of the air,as it spirals through the helix,against sidewalls of much greater surface area,robbing power,both through viscous shearing and wall friction.The turbulence created through the throttle is not the source of pumping-losses,as is the manifold vacuum,not present in a diesel ( as it has no throttle ).Diesels benefit from their lack of a throttle,and fact that pound for pound,Diesel fuel has about 11 % more Btus than gasoline.The increased mass of Diesel reciprocating components,works counter to a Diesel's efficiency at high speeds.Typically,my gasoline pickup truck gets better mileage than a VW Rabbit turbo-diesel,at 80 mph.Throttles can be sized to run at WOT during cruise (as is done in carbuteted HONDAs ),achieving low pumping losses and high mpg.