Return-Path: Received: from [24.25.9.103] (HELO ms-smtp-04-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 4.2b3) with ESMTP id 3228184 for flyrotary@lancaironline.net; Wed, 12 May 2004 08:24:08 -0400 Received: from EDWARD (clt25-78-058.carolina.rr.com [24.25.78.58]) by ms-smtp-04-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id i4CCO5C9002198 for ; Wed, 12 May 2004 08:24:06 -0400 (EDT) Message-ID: <001c01c4381c$0550fd10$2402a8c0@EDWARD> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Runner Length Date: Wed, 12 May 2004 08:24:06 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0019_01C437FA.7E0ADF90" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1409 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2800.1409 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_0019_01C437FA.7E0ADF90 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable ----- Original Message -----=20 From: Al Gietzen=20 To: Rotary motors in aircraft=20 Sent: Wednesday, May 12, 2004 1:43 AM Subject: [FlyRotary] Re: Runner Length Al, focusing on the losses at these velocities and thinking that = re-accelerating the column of air in the intake tract is a bad thing = misses the point entirely. That's like saying a supercharger will drop = horsepower because it takes power from the engine to turn it. Well; I don't think it misses the point entirely. I was just = pointing out that accelerating the air uses energy, which is a negative = in addition to other losses (reducing manifold pressure). I didn't mean = to imply that you couldn't get it back in a greater charge - it's just = not free.=20 And, of course we must keep in mind that inertial effect is = separate from the harmonic effect. Here is a link to a pretty good explanation of how to select = the correct intake runner length: http://www.hotrod.com/projectbuild/113_9907_efi/ They say that the runner length should equal the third = harmonic wavelength.=20 Al I think one needs to use caution in attempting to apply "equations" and = "calculators" designed for tuning reciprocating engines to the rotary = engine.First, you need to know which port event they are using. For = instance,many (most?) used the pulse that rebounds from the closing port = event and theychose the runner length that will return the pulse at the = proper time to the originating port.Some of themreturn the pulse as the = intake port is opening, some return it as theintake port is closing. = Clearly, these factor are factored into theirequations, but if you are = uncertain about which they use you could be choosingan non-optimum = runner length. For example in the DIE of the rotary, it doesnot return = the pulse to the originating port but sends it over tothe other rotor's = intake port. Also, the dominate "tuning" pulse usedin the DIE is not = the "inertia rebound" (although it does play a role)of the closing port, = butinstead is the more powerful pulse generated by the residue exhaust = gastrapped during the exhaust phase which bursts out into the intake = when the intakeport next opens. All these factors can make a difference = in what runner length is "right"for your installation. So just need to = be aware that apples and applesare sometimes apples and oranges.FWIWEd = Anderson ------=_NextPart_000_0019_01C437FA.7E0ADF90 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

----- Original Message = -----

From:=20 Al = Gietzen=20
To: Rotary motors in = aircraft

Sent: Wednesday, May 12, 2004 = 1:43=20 AM

Subject: [FlyRotary] Re: Runner = Length

Al, focusing on the = losses at=20 these velocities and thinking that re-accelerating the column of air = in the=20 intake tract is a bad thing misses the point entirely. That's = like=20 saying a supercharger will drop horsepower because it takes power = from the=20 engine to turn it.

Well; I = don=92t=20 think it misses the point entirely. =20 I was just pointing out that accelerating the air uses = energy,=20 which is a negative in addition to other losses (reducing manifold=20 pressure). I didn=92t mean to imply that you couldn=92t get it = back in a=20 greater charge =96 it=92s just not free.

And, of=20 course we must keep in mind that inertial effect is separate from = the=20 harmonic effect.

        Here=20 is a link to a pretty good explanation of how to select the correct = intake=20 runner=20 = length:

        http://www.hotrod.com/projectbuild/113_9907_ef= i/

        They=20 say that the runner length should equal the third harmonic wavelength. =
Al

I think one needs to use caution in attempting to apply = "equations" and
"calculators" designed for tuning = reciprocating engines to the rotary engine.
First, you need to = know which port event they are using. For instance,
many = (most?) used the pulse that rebounds from the closing port event and = they
chose the runner length that will return the pulse at the = proper time to the
originating port.
Some of = them
return the pulse as the intake port is opening, some = return it as the
intake port is closing. Clearly, these = factor are factored into their
equations, but if you are = uncertain about which they use you could be choosing
an = non-optimum runner length. For example in the DIE of the rotary, it = does
not return the pulse to the originating port but sends it = over to
the other rotor's intake port. Also, the dominate = "tuning" pulse used
in the DIE is not the "inertia rebound" = (although it does play a role)
of the closing port, = but
instead is the more powerful pulse generated by the = residue exhaust gas
trapped during the exhaust phase which = bursts out into the intake when the intake
port next opens. =
All these factors can make a difference in what runner length = is "right"
for your installation. So just need to be aware = that apples and apples
are sometimes apples and = oranges.

FWIW

Ed = Anderson

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