Lamellar self-blocking grille - Page 3 - Fuel Economy, Hypermiling, EcoModding News and Forum

Big Dave · 04-12-2009, 11:34 PM

Looks like a good idea but it is probably beyond the capability of any DIYer.

You'd have to get the airfoil shape, pitch and spacing JUST RIGHT for it to work worth a hoot.

You could guess, I suppose, but what good is a design based on a WAG?

Frank Lee · 04-13-2009, 01:31 AM

Oh, I don't know about that. The geometry of it is laid out right in this thread. Can't be that tough.

winkosmosis · 04-13-2009, 02:30 AM

Do they really have to be aerofoil shaped? Why not just curved flat slats?

I'm sure you could find some product with the right shapes that you can cut to fit your grill opening.

Nigel · 04-13-2009, 02:42 AM

I think it would probably work to some extent even with plain flat bars, angled and spaced correctly.
Rolls Royce silver shadows have a strangely similar setup - only vertical. I know FE was not a factor in that design, but quietness was and they had no lack of aero expertise at the time.

cfg83 · 04-13-2009, 02:54 AM

TestDrive -

Quote:

Originally Posted by TestDrive

Any reason to assume it's a scale drawing and not just an artists rendition?

...

That's a good question. Because it's all I have to work with, I am just trying to analyze it for what it is (in the hopes that someone will make one).

Hmmmmmm. If you had one of those weather "wind speed indicators" behind a dummy "grill box", you should be able to stick it out the window and see the grill block "close" at higher speeds.

CarloSW2

lunarhighway · 04-13-2009, 04:04 AM

autospeed did a quite comprehensive article about pressure measurement and even explained how to make a lo-fi pressure gauge with just a bottle and some tubing...
so provided you have a means of measuring the pressure you could do an A-B test where you test the pressure behind the grill with and without certain mods... if you make the airfoils angle adjustable you could even experiment with the optimal setup.

cmroseberry · 04-13-2009, 05:37 AM

For figures illustrating what I wrote about previously, see
http://etd.lib.ttu.edu/theses/availa...5018971985.pdf
Alternatively, one can google "ram coefficients Pritchard" and find the same thesis. Check-out the figures on pages 6 and 26 (pages 15 and 35 of the pdf file).

Shawn D. · 04-13-2009, 01:15 PM

First off, you can't "scale" the grille from drawings or pics to suit your car. Even if the principle worked (which I don't believe), the Reynolds number would be wrong and you haven't accounted for the rest of the shape of the nose.

I'm with cmroseberry -- I don't believe the theory that the flow splits differently based on speed. There's nothing in aerodynamic theory or practice that would support this. Yes, I am an aerospace engineer.

cfg83 · 04-13-2009, 01:20 PM

Shawn D -

Quote:

Originally Posted by Shawn D.

First off, you can't "scale" the grille from drawings or pics to suit your car. Even if the principle worked (which I don't believe), the Reynolds number would be wrong and you haven't accounted for the rest of the shape of the nose.

I'm with cmroseberry -- I don't believe the theory that the flow splits differently based on speed. There's nothing in aerodynamic theory or practice that would support this. Yes, I am an aerospace engineer.

Most egg-salad. I am going to ask my Dad. He worked on Apollo, so I will get (yet) another engineer's opinion.

CarloSW2

Frank Lee · 04-13-2009, 05:24 PM

It's not rocket science!