<VV> Re: fan tests, vanes,etc

[djtcz at comcast.net]

snipped and bottom posted

-------------- Original message -------------- 

> ----- Original Message ----- 
> From: "BBRT" 
> To: 
> Sent: Friday, August 12, 2005 10:02 PM 
> Subject: Air distribution on cylinders - stock Corvair 
> 
> 
> >I do not believe the air distribution is equal on all cylinders. The stock 
> >type of fan, the direction of air flow, the crudeness of the shroud shape > >lacking internal flow vanes (like a Porsche) lead me to believe the > >cylinders and heads do not cool evenly. The direction of flow will dictate > >if R and L side heads mirror each other, especially if direction of fan 
> >rotation are different. I haven't seen the SAE papers. Perhaps Bob could > >comment. The average on each side may be similar, but I expect exacting > >measurements would show differences. I would like to see both sides > >measured in the upcoming fan tests. Matter of fact, I'd love to see > >individual cylinder tests. 
> > 
> > Chuck S 
> > 
> > 
> > 

The SAE Corvair paper (authored by Benzinger) has a couple of pages on the development of the original cooling system.

1- One stated advantage of the vertical shaft fan location is it automatically provides more "uniform flow to the cylinders." Makes sense to me, at least to each bank of cylinders, with full peripheral discharge.  The Germans have to load their ductwork with turning vanes work to coax  their vertical fans to provide flawed but acceptable cooling for their simplified two cylinder banks. We clever Yankees have spent some time "fixing" it.
http://www.sbw.org/assets/index/vw/$file/enginefront.jpg

http://www.evozine.com/images2/911.fan.jpg

http://www.i405.com/vw/stand/FanHouse_OffSetOil02.jpg

http://www.aircooledtechnology.com/type1/dtm/
http://www.aircooledtechnology.com/type1/dtm/DSCN0200.JPG

2 - Chevy started with several flow directing scrolls/diffusers inside a clear shroud and developed them to achieve uniform pressure distribution with better blower efficiency (10-15% expectation).  But on a running engine the cylinders far from the diffusers were not getting enough air flow. So they ended up cutting back and then removing the diffusers.  "As it was, blower power consumption remained unchanged with or without  (the not optimized) diffusers"

Mr B's speculative explanation for diffusers instant failure was the lack of space available.  This makes sense to, since the generic rules for fan inlet and outlet ducting is 10 fan diameters of straight duct are necessary for reasonable flow patterns to develop