Return-Path: Received: from [24.25.9.102] (HELO ms-smtp-03-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 4.2b3) with ESMTP id 3226791 for flyrotary@lancaironline.net; Tue, 11 May 2004 12:17:31 -0400 Received: from EDWARD (clt25-78-058.carolina.rr.com [24.25.78.58]) by ms-smtp-03-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id i4BGHSs2012135 for ; Tue, 11 May 2004 12:17:29 -0400 (EDT) Message-ID: <000e01c43773$74c60e00$2402a8c0@EDWARD> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Runner Length Was Ref: injector relocation predictions? Date: Tue, 11 May 2004 12:17:28 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_000B_01C43751.ED7B3590" 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_000B_01C43751.ED7B3590 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MessageAl, in many of the induction articles I have read, I frequently = come across velocity flow numbers of 300-400 fps. Some caution not to = exceed airflow of mach 0.6 in the inlets. I'll find some of the = articles for you to read, it seemed high to me as well, but I ran across = it in a number of different articles.. Ed Ed Anderson RV-6A N494BW Rotary Powered Matthews, NC ----- Original Message -----=20 From: Al Gietzen=20 To: Rotary motors in aircraft=20 Sent: Tuesday, May 11, 2004 11:37 AM Subject: [FlyRotary] Re: Runner Length Was Ref: injector relocation = predictions? Now taking the fact that at 6000 rpm and 100% VE a 80 CID rotary = will suck approx 277 CFM of air, so each set of runners flow approx `1/2 = *277 or 138 CFM. Assuming that the air divides between the two runners = proportional to their areas 40% for the primary and 60% for the = secondary. We have .4*138 =3D 52 CFM and 0.6* 138 =3D 82 CFM To find the air velocity in each runner we divide the flow in each = runner by the area of that runner we find that the average velocity of = air in the intake is only on the order of 110 fps or approx 75 mph. = Now most induction theory says you want an intake velocity on the order = of 300 fps, Ed; Where does that number come from, and what does it mean? Or maybe = the better question - Where should the velocity be 300 fps, and over = what length? That is a very high velocity, and if it occurs over a very = long length of runner, there will be pressure loss. As I understand it, = in a piston engine with valves, it is good to have that kind of velocity = entering the combustion chamber for good mixing and some interia, and = maybe at the injectors (usually at the ports). In the rotary, as I = understand from talking to Paul Yaw, relatively high velocity (I don't = know how high) is good as it enters the port for the same reasons, but = the port area is rather large giving velocities much less than 300 fps.=20 Velocity in the runner contributes to the momentum as the air is = flowing into the chamber, which can be helpful, but the offset is that = it stops when the port is closed and has to be accelerated again. = Between that, and frictional and turbulence losses in the runner, I'd = just guess that 100 fps in the runner is plenty high enough. Maybe keep = the average velocity relatively lower, and use the dynamic wave to add = some energy into the port just before it closes. I have a 5" long, 44mm (~1.73") dia 3-barrel TB on my 3-rotor; one = barrel/rotor. At 6000 rpm that gives me a bit over 140 fps in the TB. = Based on my limited dyno experience, I think there would be a bit more = high-end (5000 up) power if the TB diameter were larger.=20 Or maybe the issue is - the TB barrel area is 2.34 in.2; from there = it is into a short manifold where it divides into primary and secondary = runners with a total area of 3.88 in.2 which matches the port area on = the housing fairly closely. So the velocity is relatively high in the = TB (where the secondary injectors are), which is good for vaporization = and throttle control, but then slows to about 85 fps (at 6000) in the = runners and entering the ports. =20 Let's see; does that all go into the category of rumination, of = little interest to anyone? Well; whatever, it is built and it works = fine. I suspect I will never be as ambitious as you, ED, and rebuild = the manifold 2-3 times.=20 Al ------=_NextPart_000_000B_01C43751.ED7B3590 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Message
Al, in many of the induction articles I = have read,=20 I frequently come across velocity flow numbers of 300-400 fps.  = Some=20 caution not to exceed airflow of mach 0.6 in the inlets.  I'll find = some of=20 the articles for you to read, it seemed high to me as well, but I ran = across it=20 in a number of different articles..
 
Ed
 
 
Ed Anderson
RV-6A N494BW Rotary=20 Powered
Matthews, NC
----- Original Message -----
From:=20 Al = Gietzen=20
Sent: Tuesday, May 11, 2004 = 11:37=20 AM
Subject: [FlyRotary] Re: Runner = Length=20 Was Ref: injector relocation predictions?

 

Now=20 taking the fact that at 6000 rpm and 100% VE a 80 CID rotary will = suck=20 approx 277 CFM of air, so each set of runners flow approx `1/2 *277 = or 138=20 CFM.  Assuming that the air divides between the two runners=20 proportional to their areas 40% for the primary and 60% for the=20 secondary.  We have .4*138 =3D 52 CFM and 0.6* 138 =3D 82=20 CFM

 

To=20 find the air velocity in each runner we divide the flow in each = runner by=20 the area of that runner we find that the average velocity of air in = the=20 intake is only on the order of  110 fps or approx 75 mph.  = Now=20 most induction theory says you want an intake velocity on the order = of 300=20 fps,

Ed;

 

Where = does that=20 number come from, and what does it mean?  Or maybe the better = question=20 - Where should the velocity be 300 fps, and over what length? =  That is=20 a very high velocity, and if it occurs over a very long length of = runner,=20 there will be pressure loss.  As I understand it, in a piston = engine=20 with valves, it is good to have that kind of velocity entering the=20 combustion chamber for good mixing and some interia, and maybe at = the=20 injectors (usually at the ports).  In the rotary, as I = understand from=20 talking to Paul Yaw, relatively high velocity (I don=92t know how = high) is=20 good as it enters the port for the same reasons, but the port area = is rather=20 large giving velocities much less than 300 fps.

 

Velocity in the=20 runner contributes to the momentum as the air is flowing into the = chamber,=20 which can be helpful, but the offset is that it stops when the port = is=20 closed and has to be accelerated again. Between that, and frictional = and=20 turbulence losses in the runner, I=92d just guess that 100 fps in = the runner=20 is plenty high enough.  Maybe keep the average velocity = relatively=20 lower, and use the dynamic wave to add some energy into the port = just before=20 it closes.

 

I have = a 5=94=20 long, 44mm (~1.73=94) dia 3-barrel TB on my 3-rotor; one = barrel/rotor. At 6000=20 rpm that gives me a bit over 140 fps in the TB.  Based on my = limited=20 dyno experience, I think there would be a bit more high-end (5000 = up) power=20 if the TB diameter were larger.

 

Or = maybe the=20 issue is =96 the TB barrel area is 2.34 in.2; from there = it is into=20 a short manifold where it divides into primary and secondary runners = with a=20 total area of 3.88 in.2 which matches the port area on = the=20 housing fairly closely.  So the velocity is relatively high in = the TB=20 (where the secondary injectors are), which is good for vaporization = and=20 throttle control, but then slows to about 85 fps (at 6000) in the = runners=20 and entering the ports. 

 

Let=92s see; does=20 that all go into the category of rumination, of little interest to = anyone?=20 Well; whatever, it is built and it works fine.  I suspect I = will never=20 be as ambitious as you, ED, and rebuild the manifold 2-3 times.=20

 

Al

 

 

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