<VV> fanz - SPAL #30102113

Thu Aug 4 00:10:08 EDT 2005

The one thing now addressed about the orifice (which likely does not apply
in this case is there is a point where no matter how much pressure you add
the flow does not increase - choked flow.
Reynolds numbers - I need to get out the books but given the speed of the
airflow I would expect the number to be on the low side.  Given the surface
finish and the turbulence I would not be surprised to see turbulent flow.
On the plus side the surface roughness, turbulence, and fin spacing would
all but eliminate and possibility of detached flow.

The Artful Dodger

> From: "Roger Gault" <r.gault at sbcglobal.net>
> Date: Wed, 3 Aug 2005 22:56:25 -0500
> To: "Corvair List" <virtualvairs at corvair.org>
> Subject: Re: <VV> fanz - SPAL #30102113
> 
> Under no circumstances will higher pressure across the fins result in lower
> flow.
> Even if a transition between laminar and turbulent flow was taking place as
> the pressure goes up, the slope of the mass flow vs pressure curve will
> never go negative.  In our case, with less than 1/8" fin spacing, I
> seriously doubt the flow between the fins is anything but essentially
> laminar.  The air can't get far enough from the surface for the flow to
> break up.  I'll admit I could be wrong here, I haven't calculated Reynolds
> Number since 1968.  AERONED!  WHERE ARE YOU?
> 
> An interesting paper can be found at:
> http://naca.larc.nasa.gov/reports/1937/naca-tn-621/
> It takes some study to understand the graphs and nomenclature, but the
> general info is easy to see.
> 
> One of the things that interests me most about it is the strong relationship
> of pressure drop to fin spacing at a fixed mass flow rate.  It really
> reinforces the need to adequately deflash our heads.  And, it argues for the
> 1/8" drill method since that opens up the spacing considerably.
> 
> I'd wager that the guys who have these electric fan cooled engines have done
> everything they could think of to help them cool, including fanatically
> deflashing the heads.  I'm also really curious how well deflashed the heads
> were in the GM tests.
> 
> By the way.  If you guys haven't looked at these reports, you've missed a
> valuable resource.  Yes, they're old.  But air is still air, even if it does
> have more junk in it these days.
> 
> Roger
> 
> 
> ----- Original Message -----
> From: "Bill & Chris Strickland" <lechevrier at earthlink.net>
> To: <virtualvairs at corvair.org>
> Sent: Wednesday, August 03, 2005 4:16 PM
> Subject: Re: <VV> fanz - SPAL #30102113
> 
> 
>> ronh at owt.com wrote:
>>> 
>>> that is the pressure needed to get enough air flow through the fins
>>> to cool it adequately.
>> 
>> Please cite the source of your data. We know there is a pressure
>> build-up -- GM supplied the data -- does the same article address a
>> 'need' for this pressure, or like you, is it just assumed?
>> 
>> There is some evidence of wasted energy in the fan system -- could using
>> a fan as an air compressor account for this waste? Ten inches of water
>> is about 1/3 of a psi. This compressed air flow probably in itself
>> produces a turbulence through the cooling fins which is not conducive to
>> maximizing flow rates -- max flow occurs with a more laminar flow
>> (example: polished intake ports), ie, if the fan wasn't trying to over
>> blow the cooling air, would more air actually flow through the fins?
>> Would more air mean a cooler engine? Or would it be cooler with a more
>> turbulent flow? Did GM engineer it this way, or did they just settle for
>> a system that sorta worked with the technology/money that was available?
>> Their concept cammer engine had three vertically oriented axial fans --
>> is there any data for this motor?
>> 
>> These are just questions -- does anyone know of data in the literature
>> to support or deny any of this?
>> 
>> Is there any data for air flow out the bottom/back of the engine, either
>> volume or temperature? Is it related to say rpm or horsepower or oil
>> temp?
>> 
>>> Since a fan [he means an electric, I presume] can only develop 10% of
>>> the pressure of the Corvair blower at the required mass flow rate ...
>> 
>> Again, where do you get the information about max pressure developed by
>> an electric fan such as the ones under discussion? Did you find a
>> definition of what Spal calls 'Static pressure' and their test method?
>> 
>> I really think that there is a possibility that there are some
>> unanswered questions concerning the Corvair cooling system that if we
>> had answers for, we could perhaps prolong the life of these little cars
>> that we so like to drive -- new heads are getting harder to find these
>> days and if anyone starts up a reproduction run, would we be able to
>> afford them if they did? We probably need to preserve what we've got,
>> and any new information that may show a better way to operate our little
>> cars should not just be dismissed because "we've always done it *this*
>> way."
>> 
>> Drive On!
>> 
>> Bill Strickland
>> _______________________________________________
>> This message was sent by the VirtualVairs mailing list, all copyrights are
> the property
>> of the writer, please attribute properly. For help,
> mailto:vv-help at corvair.org
>> This list sponsored by the Corvair Society of America,
> http://www.corvair.org/
>> Post messages to: VirtualVairs at corvair.org
>> Change your options:
> http://www.vv.corvair.org/mailman/options/virtualvairs
>> _______________________________________________
> 
> _______________________________________________
> This message was sent by the VirtualVairs mailing list, all copyrights are the
> property
> of the writer, please attribute properly. For help, mailto:vv-help at corvair.org
> This list sponsored by the Corvair Society of America, http://www.corvair.org/
> Post messages to: VirtualVairs at corvair.org
> Change your options: http://www.vv.corvair.org/mailman/options/virtualvairs
> _______________________________________________