X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from ms-smtp-01.southeast.rr.com ([24.25.9.100] verified) by logan.com (CommuniGate Pro SMTP 5.1.11) with ESMTP id 2270710 for flyrotary@lancaironline.net; Sat, 18 Aug 2007 10:40:24 -0400 Received-SPF: pass receiver=logan.com; client-ip=24.25.9.100; envelope-from=eanderson@carolina.rr.com Received: from edward2 (cpe-024-074-103-061.carolina.res.rr.com [24.74.103.61]) by ms-smtp-01.southeast.rr.com (8.13.6/8.13.6) with SMTP id l7I36QPq011952 for ; Fri, 17 Aug 2007 23:06:26 -0400 (EDT) Message-ID: <000b01c7e144$f3dfbaa0$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Air/fuel flow Date: Fri, 17 Aug 2007 23:07:46 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0008_01C7E123.6C6EBC90" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.3138 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.3138 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_0008_01C7E123.6C6EBC90 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable 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 ------=_NextPart_000_0008_01C7E123.6C6EBC90 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
George, nothing magic about 120 MPH (unless = you're in free=20 fall {:>)).  As you noted the airflow inside a carb can  = vary=20 greatly.  176 fps was just a wag that I felt comfortable with using = as an=20 example of how to find the size opening IF you desired that air velocity = at that=20 CFM flow rate..
 
Also even if you don't have a venture like in a = carb, you=20 will still reach a choke velocity - it will just be at a bit higher rate = of=20 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 = opening=20 to get that velocity OR you can pick a carb with a specific opening and = see what=20 velocity that gives you.  As long as you are below choke velocity = you are=20 probably  OK.  As you noted larger openings as on race cars = can result=20 in less velocity, but since they are bigger, you still get a lot air = mass. =20 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=20 {:>))
 
Ed
----- Original Message -----
From:=20 George=20 Lendich
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 = freefall position........Just=20 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 second.=20 Can you clarify where you acquired that figure from as a = higher=20 figure would reduce the inlet area = calculations.
 
The carb I am looking at is = the=20 Revmaster, they currently only have 40mm carbs available due = to slow=20 demand of the 42/44mm. One good thing is that the carb = operates=20 without a need of venturi, however the vacuum = signal must=20 be weaker ( because of this)coupled with a weaker signal = because of=20 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), but=20 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 and=20 velocity figures, but these may be derived from piston = engine type=20 figures.
 
If you or Lynn could = comment on this it=20 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 though=20 the density of the air is lower ( at altitude) the flow = remains the=20 same - therefore richer mixture. Revmaster says their needle = design=20 is self leaning ( to a degree) because of design. = I assume=20 because the air density directly affects the suction to the = rear=20 side of the flat ground needle, ( this provides the low = pressure=20 area rather than the venturi) therefore with reduced = density=20 you have reduced suction and reduced fuel and leaner = mixture.=20 However I will clarify that when next we 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 CFM=20 to cubic feet per second were have 176Ft^3/min / 60 = Second/Minute =3D=20 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 Date:=20 17/08/2007 5:43 PM
------=_NextPart_000_0008_01C7E123.6C6EBC90--