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From: Jeff Walin <jwalin@earthlink.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
In-Reply-To: <list-3757934@logan.com>
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Subject: Re: [FlyRotary] Intake velocity stack lengths
Date: Wed, 15 Jul 2009 06:32:54 -0500
References: <list-3757934@logan.com>

My Armchair Experts Opinion....

1. You are likely to make a very loud intake system with this idea.   
This may not be a concern.

2. You pretty much eliminate the Hemholtz style tuning system unless  
you have some continuous length 'column of air' that is the same cross  
sectional area.   The way it works is you have a vibrating mass of air  
due to the volume of air contained in the 'restricted cross sectional  
area' portion.  The momentum of this 'mass of air' is where we gain  
the benefit, as it allows more flow into the chamber because of its  
momentum.  With a continuously varied cross sectional area, you would  
have no tuned mass, therefore no momentum of this 'column of air.'

3.  Velocity stacks are there to guide flow.  Think of it this way....  
atmospheric air has little momentum (within the controlled environment  
of this theory), and the tuned column of air in your Hemholtz style  
intake system has its momentum.  So you have a problem of a high  
energy vibrating air mass at the tip of your column interacting with  
normal atmospheric air.  The tip of your column of air will cause all  
kinds of pressures and reflections and refractions and all this will  
impede flow.  The bell end of the intake acts to guide the air and  
allow it to work across this transition.

4.  I think there would be no problem in longer, larger bell ends, but  
if you eliminate the tuned continuous cross sectional area column of  
air, then you are not using Hemholtz theories of tuned systems, and  
who knows what would happen.

5. I think carbon fiber is fine for intake systems, as long as the  
materials can resist direct contact with fuel.  I'm talking about the  
P part in FRP.  (Fiber Reinforced Plastic)

Jeff

p.s. this advice is worth exactly what you pay for it....


On Jul 14, 2009, at 8:33 PM, Ben Schneider wrote:

>
> Fellows,
>
>  I have been thinking up this crazy idea of trying to make intake  
> runner tubes out of carbon fiber. My question is regarding length of  
> the velocity stack. Does the length make a difference? Could a  
> velocity stack be more or less the entire length of the tube?  
> Meaning, if I have a 12" intake tube, could the entire length of the  
> tube be a gradual taper to the diameter of the block opening? Would  
> that mess with the speed the air is traveling in the tube?  
> Aerodynamics is not something I have a very good handle on, and am  
> hoping someone out there in Fly Rotary land can shed some light.
>
> Toughts???
>
> BTW,  Any reasons why carbon fiber should not be used for intake  
> tubes? May make the velocity tubes a mute point.
>
> Thanks for any thoughts.
>
> Ben Schneider
>
> P.S. Any Fly Rotary fellows going to OSH??? Perhaps a lunch one day  
> or something.
>
>
>
>
> --
> Homepage:  http://www.flyrotary.com/
> Archive and UnSub:   http://mail.lancaironline.net:81/lists/flyrotary/List.html