Screw Feeder Volume
This section of the formula is based on the Theory of Pappus, equating the area of the relatively thin boundary layer being equal to the width times the circumference, c x Pi x D, where D is the mean diameter. I think that there is another bracket mising in the original and the it would be easier to appreciate the figures if written C(2 Ro + c/2), which is then multiplied by Pi to get the area of the extra ring of material.
Interpreting this phenomenon in practice calls for some experience but, fortunately for amateur designers, sensitive discharge rates can be secured by speed control, rather than depending on fine assessment of volumetric capactity or transfer efficiency. It is more crucial when progressive extraction is important, particualrly at the exit end of the hopper, but that is a usually matter for specialists ■
Re: Screw Feeder Volume Question
Thank you.
The bracket was probably where I was getting confused the most. ■
Screw Feeder Volume Question
I need a little help in solving a little puzzle with regard to the volume of material discharged by a screw feeder in the last pitch before the choke section. I am reading the "On Hopper Geometry Interfacing with a screw feeder to achieve Uniform Draw-Down Performance" by Y. Yu and P.C. Arnold paper and on page 34 (Page 2 of your printout) the formua for effective area doesnt make sense to me.
Ae=[(Ro^2 - Rc^2) + (1-k)(2cRo + c^2)]
where
Ro = Outside radius of flight
Rc = Radius of Core shaft
c = clearance between casing and screw flight
k = coefficient to account for possible dead layer of material at base
(k=0 if the material slips off the casing wall and k=1 if there is a dead layer not moving at all)
I cannot understand how the "(2cRo + c^2)" comes from. Specifically 2cRo is causing confusion as the rest of the formula can be dictated by the cylindrical volume formula.
Any pointers would be appreciated. ■