Message-ID: <3F723E76.5000501@netdoor.com>
Date: Wed, 24 Sep 2003 20:01:42 -0500
From: Charlie & Tupper England <cengland@netdoor.com>
Reply-To: cengland@netdoor.com
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: DIE the short Answer
References: <list-2602203@logan.com>
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Ed Anderson wrote:

>----- Original Message -----
>From: "Charlie & Tupper England" <cengland@netdoor.com>
>To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
>Sent: Wednesday, September 24, 2003 2:49 PM
>Subject: [FlyRotary] Re: DIE the short Answer
>
>
>  
>
>>Russell Duffy wrote:
>>
>>    
>>
>>>We somehow have to keep the lower pressure in the manifold (at idle for
>>>example) from sucking the rubber tubes closed.  So the concept is
>>>..err great, err, but needs some more  work on the details{:>)
>>>
>>>
>>>Two words- slide trombone :-)
>>>
>>>Rusty (I'll just turn up the boost)
>>>
>>>      
>>>
>>Mazda did the slide thing on the LeMans winner. Remember, car engines
>>must produce torque over a much wider range than a/c engines. I'm
>>looking forward to seeing a VE plot vs RPM using Ed's formulas &
>>manifold. How much detuning is there between 5000 & 6000 RPM?
>>
>>Charlie
>>
>>    
>>
>
>Hi Charlie
>
>Mazda did something that appears similar in some respects.  They did indeed
>have pipe intakes that they could vary the length of to get better airflow
>matching with RPM.  This was an excellent example of "Organ Pipe" tunning.
>However, that engine did not use the EDDIE.  It had 3 spark plugs, 10:1
>compression rotors, unrestricted intake (I think they even used a "slide"
>throttle body so at WOT there would be nothing in the way of air flow)  With
>4 rotor it had no problem getting to 6000 rpm against any load that little
>race car body weight might have produced {:>).
>
>I would love to provide a Ve plot vs rpm. However, I think we would have to
>put the system on a dyno to get the data.  One way of looking at the EDDIE
>is that it does, in effect, increase Ve (Volumertic efficiency).  My
>calculations indicates max increase is around 115%.   And for that
>particular figure it was for around 5700 rpm.  I would expect approx the
>same through at least 6500 rpm.  Some things start to happen above that rpm
>that makes me leery of hazarding any further extrapolation.
>
>Not quite certain exactly what you are referring to by detuning between 5000
>and 6000 rpm?  If you mean the "bandwidth" of the EDDIE then it depends on
>several factors.  Most of the effect falls in a region below the EDDIE rpm.
>There are things you can do to broaden the bandwidth.  However, when you do
>that,  you are diluting the EDDIE by spreading the resulting energy over a
>wider band.  Same amount of total energy, so if you spread it you reduce the
>energy at the peak.  Now reducing the "Peakiness" for an non racing
>automobile may be benefical, but for a  racer and aircraft use, we might be
>more interested in keeping the EDDIE at the "sweet spot" rpm.  I think that
>is one reason they didn't use the EDDIE on the LeMans.  Also, using the
>"Organ Pipe" approach you don't have to have tubes sliding inside of tubes
>to keep the effect on the rpm {:>).
>
>At least that is my take on it.  Could be wrong, have been before and will
>be again.
>
>Be seeing you in about 1 1/2 weeks, Charlie (provide the Wx holds good)
>
>Ed Anderson
>
Hi Ed,

I was trying to ask about the Q, or 'peakiness' of the tuning technique. 
My point about the 5k to 6k rpm is that with the 2.17 gearbox, rpms 
outside that range aren't of any real interest in a fixed pitch a/c 
engine application. Even with a fairly high 'Q', if you tune for your 
expected cruise rpm (somewhere between 5k & 6k?) how much will you give 
up if you don't have in-flight adjustable tube length? My assumption is 
that with a fixed pitch prop on a fast clean plane like the RV-class 
planes, you will turn at least 5k when you begin the takeoff roll & not 
exceed 6k or you will run into problems with the prop tips approaching 
the sound barrier. Is the peak so sharp that it will require varying the 
tube length over a 1k rpm band?

I realize that the Lemans racer was using the variable helmholtz tuning 
method, but the variable length intake pipes were intended to move the  
torque peak over a several thousand rpm range to allow accelerating out 
of 20 mph curves & still pull well at 240 mph. My confusion is why 
tuning over a several thousand rpm range is needed in an a/c (Unless of 
course the Eddie effect is EXTREMELY high Q requiring tuning over a 1k 
range).

Or have I completely missed the point & the goal is actually to tune for 
air temperature?

(now even my fingers hurt.)

Charlie