----- Original Message -----

From: H & J Johnson

To: Rotary motors in aircraft

Sent: Friday, November 09, 2007 2:03 PM

Subject: [FlyRotary] Re: Total,duct, Ambient or Velocity????

It would.. there are those out there who are already there to some

extent.. all systems have to have a 'first run' at some point :-)

Throwing some computer validation into the mix always adds

another level of 'fun' to the process.

I'm  finishing a job right now that had somewhere around 5000

parts in it, it's all modeled via 3D design and it's been fitting together

amazingly well..  there have been VERY few parts that needed to

be touched up to fit.. it's great to see parts coming from all over

North America that come to the shop and bolt on w/ the first try..

I'm hoping to be able to do this w/ a larger portion of my

project .. when I get that far along :-)

Anyway, it's not to say that computers haven't been a HUGE help

in the way things are designed today.. but they still aren't completly

and entirely absolute for the entire project.. I'm not sure we'll

ever get there in my day.. and I'm not to 'well aged' yet.. :-)

 

Jarrett

 

> Yes, Jarrett,  it would be very  interesting to design a cooling
> system using CFD, fabricate, install and test it to see the
> results. 
>
> Ed
>  ----- Original Message -----
>  From: H & J Johnson
>  To: Rotary motors in aircraft
>  Sent: Friday, November 09, 2007 11:40 AM
>  Subject: [FlyRotary] Re: Total,duct, Ambient or Velocity????
>
>
>
>
>
>  > But, semantics aside, yes, I agree, lower exit pressure is
> what
>  > you are after and that does not always equate to larger exit
> duct
>  > area.  In fact, if the air heated by the core flows through a
>  > nozzle it might even produce thrust and lower exit pressure
> using
>  > a smaller exit.  But, in general, I still believe that in most
> of
>  > our cases, we are short of the level of duct design that would
>  > reliably permit that.  What we need is someone to invest in
> one of
>  > those $$$$ Computer Fluid Flow software programs and see what
> they
>  > would reveal.
>  >
>  > Ed
>  >
>  >
>  > Ed,
>  >
>  > I have to disagree with the big $$$ CFD idea. Until I see
> proper
>  > exit ducts and every effort made to do things right inlet
>  > wise....CFD is a waste of time. I have yet to see an
> installation
>  > at the level of refinement where CFD would start to make
> sense.
>  > You can get to 90% of optimum by following a few simple
> guidelines
>  > and some fairly simple math.
>  >
>  > 1.) do a heat balance at the cruise condition to figure out
> how
>  > much air you need to ingest.
>  >
>  > 2.) Size your inlet appropriately.
>  >
>  > 3.) Provide a real exit duct.
>  >
>  > 4.) Use a cowl flap.
>  >
>  > 5.) Do some testing with oil and tufts to make improvements.
>  >
>  > A properly done CFD will only get you another 5% beyond these
>  > simple steps that are within reach of mere mortals. In fact if
> the
>  > guy/gal doing the CFD work is not intimately familiar with the
>  > situation and what sort of assumptions to make/conditions to
>  > assign it is very likely that the results will be less
> successful
>  > that the empirical method.
>  >
>  > In other words CFD=decimal dust.
>  >
>  >
>  > Monty
>
>
>  Well.. I haven't spent $$$ on it but SolidWorks now comes w/ a
> version of
>
>  CosmosFloWorks in the package in 2008..  I've got the software
> so I may give it
>
>  a whirl.. I was waiting to test it before I commented but..
> since people are talking
>
>  directly about it..  :-)
>
>
>
>  Jarrett
>
>
> --
>
> Homepage:  http://www.flyrotary.com/
>
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