Return-Path: Received: from [24.25.9.100] (HELO ms-smtp-01-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 4.2) with ESMTP id 363260 for flyrotary@lancaironline.net; Fri, 13 Aug 2004 00:36:17 -0400 Received-SPF: none receiver=logan.com; client-ip=24.25.9.100; envelope-from=eanderson@carolina.rr.com Received: from EDWARD (cpe-069-132-183-211.carolina.rr.com [69.132.183.211]) by ms-smtp-01-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id i7D4ZhPg015973 for ; Fri, 13 Aug 2004 00:35:45 -0400 (EDT) Message-ID: <002001c480ef$01eb1860$2402a8c0@EDWARD> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Turbos from the land of Oz Date: Fri, 13 Aug 2004 00:35:48 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_001D_01C480CD.7AA76BE0" 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_001D_01C480CD.7AA76BE0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Hi Mick, thanks for confirming the more air less boost. I was a bit = concerned when you first mentioned more boost as that is not what we = need. From what I could tell about the mod from the photos on Macs web site. = This is how their modification works to produce more air flow but less = boost. First, they replace the stock compressor wheel with one of larger size. = Second, they reduce the effect of the exhaust mass flow on the turbine = wheel by enlarging the exhaust exit around the turbine blades permitting = some exhaust gas to slip by without imparting energy to turning the = turbine wheel and they all also enlarge the waste gate port. These both = reduce the RPM of the turbine/compressor wheel rotating assembly. The results is you have a larger compressor wheel/blades which is = turning slower However, the larger/longer blades of the bigger = compressor wheel is "grabbing" more air on each revolution than did the = stock wheel. Now , since the compressor wheel is spinning slower due to = the exhaust mass flow diverted around the turbine wheel you get more air = volume (but less air velocity ) from the compressor blades. Also the = outlet nozzle of the compressor housing is a diffuser (slows down the = air and creates pressure). I suspect that they might also enlarge the = exit nozzle inner diameter as this will also reduce the conversion of = air velocity to pressure but I don't recall reading that so perhaps they = leave it alone.. =20 Mass flow =3D pVA (density, Velocity, Cross sectional Area) provides = the key to the reason enlarging the compressor exit nozzle (diffuser) = reduces boost. The mass continuity law says that the product does not = change - so if suddenly the mass flow encounters a larger area (A = increases) then Velocity must decrease to maintain a constant product. = Here its simply the dynamic pressure equation 1/2 pV^2. If velocity is = decreased then the dynamic pressure equation 1/2p V^2 tells us with less = V there is less energy to convert into a pressure increase. They have lowered the velocity V of the air flow into the diffuser = therefore there is less dynamic pressure (air velocity) to convert into = pressure. In other words, boost is not conditional on the amount = (volume) of air you flow - but depends on the velocity you accelerate it = to before it flows into the diffuser (among some other factors). So = you have lower velocity giving you less boost but you still have the = larger volume of air produced by the bigger compressor wheel. Ergo, you have more air flow but less boost for the same exhaust mass = flow. =20 At least thats the way it appears to me. Ed RV-6A N494BW Rotary Powered Matthews, NC ----- Original Message -----=20 From: Michael Haynes=20 To: Rotary motors in aircraft=20 Sent: Thursday, August 12, 2004 10:36 PM Subject: [FlyRotary] Re: Turbos from the land of Oz Hay John Dropped off my turbo yesterday and confirmed more air flow less = boost! I STAND CORRECTED. I Still don't under stand. Anyway Max has = taken a lot of interest in what we are doing and is researching more on = a way to control boost at alt. He did mention that the microtec computer = that is used down here a lot does compensate boost with alt but not sure = to what alt it goes to ( designed for driving in the hills ), also has = limp home mode. Ill find out more when I see him next. =20 Cheers Mick ----- Original Message -----=20 From: John Slade=20 To: Rotary motors in aircraft=20 Sent: Wednesday, August 11, 2004 12:47 AM Subject: [FlyRotary] Turbos from the land of Oz G'day Mick > I must say you did a good job on the turbine or what was left = anyway!!!. =20 Thank you, thank you. I try hard to please. :) Thanks for the update. It's a little scary dealing with a company so = far away, but Max seems like a straight up guy so I never really had any = doubt he'd come through. Just took a little longer than I'd hoped. 400HP. Yes. he mentioned that. A bit lower at my max rpm of 6300, = but still - plenty of grunt. :) > From what he explained to me was that you will get more boost for = a slower turbine rpm, =20 I thought it was less boost for the same airflow. > He did mention something about throwing in a couple of peacock = feathers just incase you blow it again. =20 Oh! Nice touch. > Now im thinking of changing prop size. ( currently ivo 70" = variable high pitch 3 blade ) can you make any suggestions. =20 Well mines a wood 68 three blade with 314 blade area from = Performance. It'll accelerate the plane to take off in 1000 - 1500 feet = at 4300 rpm and climb quickly at 5000. It'll even climb at 2300 rpm. = Should be ideal for about 280 hp in cruise and should get me a better = top speed than a variable pitch. Given that you need 2000ft to land I'm = not sure a variable pitch prop will buy you anything on a Cozy, and = it'll probably cost you at the top end. Are you building a Cozy or an = RV? I forget. Cheers, John ------=_NextPart_000_001D_01C480CD.7AA76BE0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Hi Mick, thanks for confirming the more = air less=20 boost. I was a bit concerned when you first mentioned more boost as that = is not=20 what we need.
 
From what I could tell about the mod = from the=20 photos on Macs web site.  This is how their modification works to = produce=20 more air flow but less boost.
 
First, they replace the stock = compressor wheel=20 with one of larger size.  Second, they  reduce the effect of = the=20 exhaust mass flow on the turbine wheel by enlarging the exhaust exit = around the=20 turbine blades permitting some exhaust gas to slip by without imparting = energy=20 to turning the turbine wheel and they all also enlarge the waste gate=20 port.  These both reduce the RPM of the turbine/compressor wheel = rotating=20 assembly.
 
The results is you have a larger = compressor=20 wheel/blades which is turning slower   However, the = larger/longer=20 blades of the bigger compressor wheel is  "grabbing" more air on = each=20 revolution than did the stock wheel. Now , since the compressor = wheel is=20  spinning slower due to the exhaust mass flow diverted around the = turbine=20 wheel you get more air volume (but less air velocity ) from the compressor blades.  Also the = outlet=20  nozzle of the compressor housing is a diffuser (slows down the air = and=20 creates pressure).  I suspect that they might also enlarge the exit = nozzle=20 inner diameter as this will also reduce the conversion of air = velocity to=20 pressure but I don't recall reading that so perhaps they leave it=20 alone..  
 
Mass flow =3D pVA (density, = Velocity, Cross=20 sectional Area)  provides the key to the reason enlarging the = compressor=20 exit nozzle (diffuser) reduces boost.  The mass continuity law says = that=20 the product does not change - so if suddenly the mass flow encounters a = larger=20 area (A increases) then Velocity must decrease to maintain a constant=20 product.  Here its = simply the=20 dynamic pressure equation 1/2 pV^2.   If velocity is = decreased=20 then the dynamic pressure equation 1/2p V^2 tells us with less V there = is less=20 energy to convert into a pressure increase.
 
They have=20 lowered the velocity V of the air flow into the diffuser therefore there = is less=20 dynamic pressure (air velocity)  to convert into pressure.  In = other=20 words, boost is not conditional on the amount (volume) of air you flow=20 - but depends on the velocity you accelerate it to before it = flows=20 into the diffuser (among some other factors).   So you have = lower=20 velocity giving you less boost but you still  have the larger = volume =20 of air produced by the bigger compressor wheel.
 
Ergo, you have more air flow but less = boost for the=20 same exhaust mass flow. 
 
At least thats the way it appears to=20 me.
 
Ed
 
 
RV-6A N494BW Rotary Powered
Matthews, NC
----- Original Message -----
From:=20 Michael=20 Haynes
Sent: Thursday, August 12, 2004 = 10:36=20 PM
Subject: [FlyRotary] Re: Turbos = from the=20 land of Oz

Hay John
 Dropped off my turbo yesterday = and=20 confirmed more air flow less boost! I STAND = CORRECTED. I Still=20 don't under stand. Anyway Max has taken a lot of interest in what we = are doing=20 and is researching more on a way to control boost at alt. He did = mention that=20 the microtec computer that is used down here a lot does compensate = boost with=20 alt but not sure to what alt it goes to ( designed for driving in the = hills ),=20 also has limp home mode. Ill find out more when I see him=20 next.  
 Cheers
 Mick
----- Original Message -----
From:=20 John=20 Slade
To: Rotary motors in = aircraft=20
Sent: Wednesday, August 11, = 2004 12:47=20 AM
Subject: [FlyRotary] Turbos = from the=20 land of Oz

G'day=20 Mick
> I must say you did a good job on the = turbine or what=20 was left anyway!!!.  
Thank=20 you, thank you. I try hard to please. :)
 
Thanks for the update. = It's a=20 little scary dealing with a company so far away, but Max seems like = a=20 straight up guy so I never really had any doubt he'd come = through. Just took a little longer than I'd=20 hoped.
 
400HP.=20 Yes. he mentioned that. A bit lower at my max rpm of 6300, but still = -=20 plenty of grunt. :)
 
 > From what he = explained to me=20 was that you will get more boost for a slower turbine = rpm,  
I thought=20 it was less boost for the same airflow.
 
 >  He did = mention=20 something about throwing in a couple of peacock feathers just incase = you=20 blow it again.  
Oh! Nice=20 touch.
 
 > Now im thinking of = changing=20 prop size. ( currently ivo 70" variable = high  pitch 3=20 blade ) can you make any suggestions.  
 
Well=20 mines a wood 68 three blade with 314 blade area from = Performance. =20 It'll accelerate the plane to take off in 1000 - 1500 feet at 4300 = rpm and=20 climb quickly at 5000. It'll even climb at 2300 rpm. Should be ideal = for=20 about 280 hp in cruise and should get me a better top speed than a = variable=20 pitch. Given that you need 2000ft to land I'm not sure a = variable pitch=20 prop will buy you anything on a Cozy, and it'll probably cost you at = the top=20 end. Are you building a Cozy or an RV? I forget.
 
Cheers,
John
 
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