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A "tuned" intake covers a wide Varity of techniques ranging for Hermholtz,
RAM, Dynamic Intake, Inertia, etc,. There are basically three conceptually
different approaches although they tend to merge under certain conditions.
You have the resonant tuning, the pulse tuning and the inertia turning
concepts. However, truth be known all three phenomena occur in most intake
systems - it's a matter of emphasis.
The thing that really complicates it is the fact that within any induction
or exhaust system you have Finite Amplitude Waves - the power of these pulse
makes a 135 db sound wave very puny - these pulses can actually pound metal
apart. They do not interact linearly as do "sound waves" - in fact they can
respond in what at first seems to be weird ways. For instance they may
reverse there "polarity" depending on whether they encounter an open or
closed termination.
It has only been with the advent of digital computers has it been practical
to even try and model the effects of these waves in an induction system. I
find them fascinating.
Here are a few references that some of you might find interesting.
http://home.earthlink.net/~redcat/pulse_ram/theory.html
http://www.motionsoftware.com/simtech.htm
http://www.proracingsim.com/dynomationmainpage.htm
http://www.audietech.com/DMfeaturetable.htm
Ed Anderson
Rv-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com
http://www.andersonee.com
http://www.dmack.net/mazda/index.html
http://www.flyrotary.com/
http://members.cox.net/rogersda/rotary/configs.htm#N494BW
http://www.rotaryaviation.com/Rotorhead%20Truth.htm
-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On
Behalf Of George Lendich
Sent: Tuesday, March 30, 2010 6:22 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: P-Port performance
Thanks Bill,
I'm transposing off a larger document which was done piecemeal over a period
of time, for my own benefit and you picked me up on some transference
typo's. I've amended the attached copy.
Your right it's saying how much air you need and how fast that air will get
there (speed now included). Perhaps I shouldn't have labeled it Tuned. The
rule of thumb has been between 18 -21" for tuned manifold length ( from what
I understand) and this supports that theory. How much the reflected wave
affects the speed is still beyond me, at this point in time, however it you
think of the variables as Tracy suggested your going to get confused, I know
I do. This approach just gives a rough start point - it works for me however
I do find the outcomes interesting, when you do some comparisons on
variables.
George (down under)
> George,
> Why is the Renesis horsepower lower than the standard at 7500 and higher
> than the standard at 7200? It also is higher at the lower rpm??
>
> Regards the tuned length. I thought the idea was to get a reflected wave
> to
> bounce from one inlet to the other just as it was closing. If I
> understand
> what you have said, your calculation is how long a tube it would require
> to
> hold one charge of air??
>
> Bill B
>
> -----Original Message-----
> From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On
> Behalf Of George Lendich
> Sent: Tuesday, March 30, 2010 1:10 AM
> To: Rotary motors in aircraft
> Subject: [FlyRotary] Re: P-Port performance
>
>
> Cary,
> Ed came to the rescue (once again) and reminded me that was a conversion
> of
> inlet speed of 120.58 mph to seconds a minute. I adjusted the attached
> info
> sheet, to reflect this information).
>
> The maths isn't a problem, however Ed has a knack of knowing how to
> approach
> and work through a problem, whereas most of us wouldn't bother. This must
> be
> how the engineers do it to get to a start point.
>
> I don't know of anyone needing to go to 8,000 rpm and if they did they
> might
> need another ratio reduction drive, in that case they might need a
> slightly
> larger inlet. However greater VE would need to be driven by a greater
> inlet
> velocity and a bigger inlet has a reduced velocity, but I'm sure 120% VE
> is
> achievable in the racing game and much higher rpm, much as I would love to
> see it at our rpm. Then again I would love to be proven wrong. Perhaps
> with
> the higher peak inlet speed Tracy indicated was available. We won't know
> until we get mare data, perhaps from bill, down the track.
>
> Knowing how you love to dabble in things, ( nothing wrong with that) I
> included a calculation for inlet tube length, in this latest attachment -
> mind you their only ball park figures, but to me it gives a rough start
> point and an understanding of the processes involved.
> Hope that helps.
> I do have some figures on exhaust speed if your interested.
> George (down under)
>
>> Hi George;
>>
>> What is the meaning / origin of the value "176.85" in your "Diameter
>> of Inlet" calculation?
>> You should also try running your calculation with 8000rpm and 120%VE.
>>
>> SAE900032 has a bunch of useful intake and exhaust info including
>> volumetric efficiency charts versus Pport sizes and intake lengths.
>> There are other useful SAE papers that Paul posts on the other list
>> periodically.
>>
>> Cheers
>
>
> --
> Homepage: http://www.flyrotary.com/
> Archive and UnSub:
> http://mail.lancaironline.net:81/lists/flyrotary/List.html
>
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