Message-ID: <3F6E6570.2FA1726@frontiernet.net>
Date: Sun, 21 Sep 2003 22:58:56 -0400
From: Jim Sower <canarder@frontiernet.net>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: DIE Power Calculations
References: <list-2588378@logan.com>
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Ed,
<... The sound of speed (of the wave) is of course dependent on the density of
the medium it is traveling through ...>
Actually, the speed of sound in a gas is varies only with Temperature.  Not with
density.  You look at the formula for determining the speed of sound in a
particular gas, and the only variable is Ta (Absolute Temperature).  The speed
of sound also stabilizes at 575 kts (or whatever) at all "attainable" altitudes
above tropopause (36089' (standard day)).

Anyway, turbocharging increases the local speed of sound only to the extent that
it raises the temperature of the air charge.  If you start at 60 deg air,
turbocharge it to 60" MAP, could intercool it back to 60 deg, the local speed of
sound doesn't change.  Intercooling would therefore help you with stabilizing
DIE, and you would want to tune your runners to the temperature downstream of
the butterfly valve that you anticipate encountering most often in cruise.

Weird but true .... Jim S.

Ed Anderson wrote:

> Hi John,
>
>     Yes, I understood the sketch without any problem.  The divider would
> make your "Chamber" very similar to Tracy Crooks "Chamber" other than he
> uses the two secondary ports of the stock Mazda TB rather than just one
> opening.  He divides the airflow between his secondaries and primaries very
> similar to the way you do.  My "chambers" are a bit different in that I kept
> the primary and secondary runner completely separate each with their own
> throttle body opening.  But conceptually the same.
>
>    You are correct, the one absolute minimum requirement for DIE is that the
> ports MUST be interconnected without anything that might disrupted the FAW.
> I don't see where that would hurt your turbo application (in fact having
> something to sort of ensure the airflow coming in the opening is divided up
> between secondary and primary runners is probably a good idea.  Otherwise,
> path of least resistance might send more air down one set of runners and
> less down the other.  There! my short answer.
>
>  However, I am not familiar with your installation.  IF you are using an
> intercooler with your tubo (recommended), I have a feeling that the Finite
> Amplitude Wave (FA) would be disrupted to some extend by the intercooler -
> Just not certain how much and what effect that would have.  It might
> considerably diminish the DIE or not - just don't know.
>
>     But, on the other hand you are using a turbo, so while I am confident
> the DIE effect would be there, its contribution could possibly be less than
> a NA engine.  Another reason I am thinking that is I am uncertain how the
> wave's energy conversion to kinetic to dynamic pressure might be affected.
> The sound of speed (of the wave) is of course dependent on the density of
> the medium it is traveling through.  Normally in atmosphere the air density
> equates to the air temperature.  Higher temps/less dense etc.  However, in a
> turbocharge intake manifold you are going to have greater than normal air
> density and also more heat.  I think that would increase the speed of sound
> in that medium - perhaps significantly. While I would think that would
> increase the dynamic pressure recovered from the wave, don't really know.
> Even so, then that speed increase would tend to throw off any DIE
> calculations until those things were factored in.  So would the DIE
> contribution be the same, more, less when running boost - I really don't
> know.
>
>    However, on second thought, you are not going to be under boost all the
> time and DIE might well contribute to less pumping losses say at cruise
> airspeed giving you a bit of a fuel economy increase (provided the
> intercooler doesn't interfer).  So I don't see anything to lose by having
> your welder put in the divider and it might possible give a boost in some
> areas.
>
> Ed
>
> >>  Homepage:  http://www.flyrotary.com/
> >>  Archive:   http://lancaironline.net/lists/flyrotary/List.html

--
Jim Sower
Crossville, TN; Chapter 5
Long-EZ N83RT, Velocity N4095T