REFLECTOR: Nose Cooler Pressure Study

[Brent Bourgeois]

On my plane at least, the inlet scoop is big enough.( or really to big) A NACA scoop is supposed to let air in while creating very little drag, this is where our Velo-NACA is not efficient.
The exit is easy to modify with foam and duct tape and retest on each flight. Once the exit has vacuume then work on minimizing the size of the lip to reduce drag. A pressure study can point you in the right direction. Sometimes things do not work like 
you think they will.
 
brent
N61VB
Std 
--- On Sun, 10/11/09, Scott Derrick <scott at tnstaafl.net> wrote:


From: Scott Derrick <scott at tnstaafl.net>
Subject: Re: REFLECTOR: Nose Cooler Pressure Study
To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
Date: Sunday, October 11, 2009, 8:31 AM


Brent,

Great info!  What your testing suggests is the forward scoop is maxed
out and best way to increase the efficiency of the nose oil cooler is to
lower the pressure on the exit side by building up a lip or dam on the
exit hole? 

Scott

Brent Bourgeois wrote:
> Scott,
> I have spent a lot of time getting my oil cooler working properly.
> Before cutting anything, please do a basic pressure study to
> understand what is going on. All you need is a plastic tube about 1
> inch in front of the cooler and one in the exit duct. Route them
> inside and use a airspeed indicator to get an inlet press and an
> outlet press. The key is to maximize the differential. 
> I have pages of data that prove (at least on my plane ) that the
> problem is positively not getting the air in, but getting it out.
> One example is : 155mph on the pitot, 88mph on the cooler face and 10
> mph in the exit duct. I was eventually able to get the exit duct to 0.
> This 88mph proved to be the max oil cooler inlet speed all the way
> past 220 pitot speed.
> I think that once the inlet pressures up, the air stops entering and
> flows on by. Once I got max vacuum possible behind the cooler I was
> able to block off some of the (weird NACA type)  inlet and not raise
> the oil temp.
> I believe the trick is to find a reverse scoop or lip arrangement that
> maximizes the air extraction
> I had thermocouples on the cooler inlet and outlet lines. The front
> cooler is worth 15 to 20 degrees in oil temp.
> I also found this method very useful at maximizing engine cooling
> while making the air inlets smaller.
> Let me know if I can help.
>  
> Brent
> N61VB
> Std RG
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