X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from mail09.syd.optusnet.com.au ([211.29.132.190] verified) by logan.com (CommuniGate Pro SMTP 5.1.11) with ESMTPS id 2271407 for flyrotary@lancaironline.net; Sat, 18 Aug 2007 20:26:40 -0400 Received-SPF: none receiver=logan.com; client-ip=211.29.132.190; envelope-from=lendich@optusnet.com.au Received: from george (d211-31-119-28.dsl.nsw.optusnet.com.au [211.31.119.28]) by mail09.syd.optusnet.com.au (8.13.1/8.13.1) with SMTP id l7J0Pu4k015495 for ; Sun, 19 Aug 2007 10:25:57 +1000 Message-ID: <003501c7e1f7$83e56890$1c771fd3@george> From: "George Lendich" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Air/fuel flow Date: Sun, 19 Aug 2007 10:25:58 +1000 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0032_01C7E24B.550983E0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2180 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 X-Antivirus: avast! (VPS 0657-0, 12/12/2006), Outbound message X-Antivirus-Status: Clean This is a multi-part message in MIME format. ------=_NextPart_000_0032_01C7E24B.550983E0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Thanks Ed, I just thought I'd ask - just in case! If I find out I will let you and everyone else know! George George, nothing magic about 120 MPH (unless you're in free fall {:>)). = As you noted the airflow inside a carb can vary greatly. 176 fps was = just a wag that I felt comfortable with using as an example of how to = find the size opening IF you desired that air velocity at that CFM flow = rate.. Also even if you don't have a venture like in a carb, you will still = reach a choke velocity - it will just be at a bit higher rate of flow. You can have you cake one of two ways, you can decide on what velocity = you want at a certain volume flow (CFM) and then size the opening to get = that velocity OR you can pick a carb with a specific opening and see = what velocity that gives you. As long as you are below choke velocity = you are probably OK. As you noted larger openings as on race cars can = result in less velocity, but since they are bigger, you still get a lot = air mass. Pros and Cons and compromise is the name of the game. If I = had the answers, I'd be a multimillionaire consultant to NASCAR racing = teams {:>)) Ed ----- Original Message -----=20 From: George Lendich=20 To: Rotary motors in aircraft=20 Sent: Friday, August 17, 2007 9:29 PM Subject: [FlyRotary] Re: Air/fuel flow Kelly, That's interesting - is Ed trying to tell me something? Just joking, I did know that but didn't relate the two. George ( down under) George, Not Ed and not great at math but from my skydiving days the = figure of 176 feet per sec (approx 120 mph) is called terminal velocity = for the average human body in a flat stable freefall position........Just = a bit of trivia......... -- Kelly Troyer=20 "Dyke Delta"_13B ROTARY Engine=20 "RWS"_RD1C/EC2/EM2=20 "Mistral"_Backplate/Oil Manifold=20 -------------- Original message from "George Lendich" = : --------------=20 Ed, I would like to clarify another point and that is your = velocity figure of 120 mph. I will explain:- I have studied carb sites for snippets of information ( = they don't give much away), however one did say that carb choke speeds = are usually 450' per second and racing cars 125' per second. I assume the racing car inlet speeds are lower because the = throttle is wide open with massive sized inlets, therefore lower vacuum = signal. Your calculations use 176' per second. Can you clarify = where you acquired that figure from as a higher figure would reduce the = inlet area calculations. The carb I am looking at is the Revmaster, they currently = only have 40mm carbs available due to slow demand of the 42/44mm. One = good thing is that the carb operates without a need of venturi, however = the vacuum signal must be weaker ( because of this)coupled with a weaker = signal because of the shape of the rotor face.=20 At the very least the lack of venturi also eliminates the = choke potential. Some carbs have a 44mm inlet but are choked to 36mm = which would increase inlet speed (good), but as you say, may move into = the choke restriction area (bad). A weaker signal would also effect the idle mixture as this = is driven by vacuum rather than air flow, however I guess this can be = adjusted manually. Should be plenty of vacuum at idle with the slide = closed. I have asked Revmaster for air flow and velocity figures, = but these may be derived from piston engine type figures. If you or Lynn could comment on this it would be greatly = appreciated.=20 Also my research indicates that flow air/ fuel mix richens = at higher RPM and altitude. I can't remember why at higher RPM - mind = block, however for altitude it is because fuel flow is driven by air = flow and even though the density of the air is lower ( at altitude) the = flow remains the same - therefore richer mixture. Revmaster says their = needle design is self leaning ( to a degree) because of design. I assume = because the air density directly affects the suction to the rear side of = the flat ground needle, ( this provides the low pressure area rather = than the venturi) therefore with reduced density you have reduced = suction and reduced fuel and leaner mixture. However I will clarify that = when next we talk. I find this all very interesting! George ( down under) Well I'll be Ed, 2.4137sq" =3D (.877x.877xPi =3D 2.416), therefore .877 = Radius or 1.754 Dia or 44.55 mm for the carb opening. I'm working on the rest! George ( down under) For inlet, you take the CFM and you need one other factor = - what velocity do you want through your inlet? Lets say you want a = higher velocity of around 176 feet/sec (120 MPH) then we know that = Volume =3D Area * length. If were want 176 feet/sec velocity from 176 = CFM air flow then coverting CFM to cubic feet per second were have = 176Ft^3/min / 60 Second/Minute =3D 29.333 Ft^3/ Second -------------------------------------------------------------------------= - No virus found in this incoming message. Checked by AVG Free Edition.=20 Version: 7.5.484 / Virus Database: 269.12.0/959 - Release Date: = 17/08/2007 5:43 PM -------------------------------------------------------------------------= ----- No virus found in this incoming message. Checked by AVG Free Edition.=20 Version: 7.5.484 / Virus Database: 269.12.0/959 - Release Date: = 17/08/2007 5:43 PM ------=_NextPart_000_0032_01C7E24B.550983E0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
 Thanks Ed,
I just thought I'd ask - just in = case!
If I find out I will let you and = everyone else=20 know!
George
George, nothing magic about 120 MPH (unless = you're in=20 free fall {:>)).  As you noted the airflow inside a carb = can =20 vary greatly.  176 fps was just a wag that I felt comfortable = with using=20 as an example of how to find the size opening IF you desired that air = velocity=20 at that CFM flow rate..
 
Also even if you don't have a venture like in = a carb,=20 you will still reach a choke velocity - it will just be at a bit = higher rate=20 of flow.
 
You can have you cake one of two ways, you can = decide on=20 what velocity you want at a certain volume flow (CFM) and then size = the=20 opening to get that velocity OR you can pick a carb with a specific = opening=20 and see what velocity that gives you.  As long as you are below = choke=20 velocity you are probably  OK.  As you noted larger openings = as on=20 race cars can result in less velocity, but since they are bigger, you = still=20 get a lot air mass.  Pros and Cons and compromise is the name of = the=20 game.  If I had the answers, I'd be a multimillionaire consultant = to  NASCAR racing teams {:>))
 
Ed
----- Original Message -----
From:=20 George Lendich
To: Rotary motors in = aircraft=20
Sent: Friday, August 17, 2007 = 9:29=20 PM
Subject: [FlyRotary] Re: = Air/fuel=20 flow

Kelly,
That's interesting - is Ed trying = to tell me=20 something?
Just joking, I did know that but = didn't relate=20 the two.
George ( down under)
George,
    Not Ed and not great at math but from my = skydiving=20 days the figure
of 176 feet per sec (approx 120 mph) is called terminal = velocity for=20 the
average human body in a flat stable=20 freefall position........Just a bit of
trivia.........
--
Kelly Troyer
"Dyke = Delta"_13B=20 ROTARY Engine
"RWS"_RD1C/EC2/EM2
"Mistral"_Backplate/Oil = Manifold=20




--------------=20 Original message from "George Lendich" = <lendich@optusnet.com.au>:=20 --------------

 
Ed,
 I would like to = clarify another=20 point and that is your velocity figure of 120 = mph.
 
I will = explain:-
 
I have studied carb = sites for=20 snippets of information ( they don't give much away), = however one=20 did say that carb choke speeds  are usually 450' = per=20 second and racing cars 125' per second.
 
I assume the racing car = inlet speeds=20 are lower because the throttle is wide open with massive = sized=20 inlets, therefore lower vacuum signal.
 
Your calculations use = 176' per=20 second. Can you clarify where you acquired that figure = from as a=20 higher figure would reduce the inlet area=20 calculations.
 
The carb I am looking at = is the=20 Revmaster, they currently only have 40mm carbs available = due to=20 slow demand of the 42/44mm. One good thing is that the = carb=20 operates without a need of venturi, however the = vacuum=20 signal must be weaker ( because of this)coupled with a = weaker=20 signal because of the shape of the rotor face. =
 
At the very least the = lack of venturi=20 also eliminates the choke potential. Some carbs have a = 44mm inlet=20 but are choked to 36mm which would increase inlet speed = (good),=20 but as you say, may move into the choke restriction area=20 (bad).
 
A weaker signal would = also effect the=20 idle mixture as this is driven by vacuum rather than air = flow,=20 however I guess this can be adjusted manually. Should be = plenty of=20 vacuum at idle with the slide closed.
 
I have asked Revmaster = for air flow=20 and velocity figures, but these may be derived from piston = engine=20 type figures.
 
If you or Lynn could = comment on this=20 it would be greatly appreciated.
 
Also my research = indicates that flow=20 air/ fuel mix richens at higher RPM and altitude. I = can't=20 remember why at higher RPM - mind block, however for = altitude it=20 is because fuel flow is driven by air flow and = even=20 though the density of the air is lower ( at altitude) the = flow=20 remains the same - therefore richer mixture. Revmaster = says their=20 needle design is self leaning ( to a degree) because of = design.=20 I assume because the air density directly affects the = suction=20 to the rear side of the flat ground needle, ( this = provides the=20 low pressure area rather than the venturi) therefore = with=20 reduced density you have reduced suction and = reduced fuel and=20 leaner mixture. However I will clarify that when next we=20 talk.
I find this all very=20 interesting!
George ( down = under)
 
 
 
Well I'll be = Ed,
2.4137sq" =3D = (.877x.877xPi =3D 2.416),=20 therefore .877 Radius or 1.754 Dia or 44.55 mm for the = carb=20 opening.
I'm working on the = rest!
George ( down = under)
 
For inlet, you take the CFM and = you need one=20 other factor - what velocity do you want through your = inlet? =20 Lets say you want a higher velocity of around 176 feet/sec = (120=20 MPH)  then we know that Volume =3D Area * = length.  If were=20 want 176 feet/sec velocity from 176 CFM air flow then = coverting=20 CFM to cubic feet per second were have 176Ft^3/min / 60=20 Second/Minute =3D 29.333 Ft^3/=20 = Second

No virus found in this incoming message.
Checked by AVG = Free=20 Edition.
Version: 7.5.484 / Virus Database: 269.12.0/959 - = Release=20 Date: 17/08/2007 5:43 PM

No virus found in this incoming message.
Checked by AVG Free = Edition.
Version: 7.5.484 / Virus Database: 269.12.0/959 - Release = Date:=20 17/08/2007 5:43 PM
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