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Ah, well, George, if you are using a slide
throttle, then forget the spreadsheet I sent you - that was assuming a
rotating plate. In that case it will depend on the shape of your slide, if
a straight plate then the area is fairly easy to find. I am
assuming a throttle with a flat straight edge sliding plate across the throttle
area.
Since there is no revolving throttle plate, the angle in
the spreadsheet is actually the angel between the center of the circle area to
the points where the sliding plate enters the throat.
So when the plate is fully across the opening or
closed - this angle is zero, the angle is 180 deg when the plate is half
way open and 360 degree when it is fully open.
That's about all I can along these lines. If the end
of the sliding plate is anything other than straight (no "V" notches, etc) then
this is not going to be accurate.
Ed
----- Original Message -----
Sent: Saturday, September 22, 2007 8:06
PM
Subject: [FlyRotary] Re: Area of a
circle
Thanks Ed,
I'm looking at it - again!
Mind you I'm wanting to use a slide throttle, so
the butterfly thickness and rod are not a factor in my non-venturi, straight
through 44 mm dia carb design.
George
----- Original Message -----
Sent: Sunday, September 23, 2007 2:25
AM
Subject: [FlyRotary] Re: Area of a
circle
I agree with Al, George.
However, if you wish to enjoy the thrill of
calculating that area (which is not a trivial task), here is a document that
has all the information (formulas) you need.
Now if you are willing to
assume that the throttle plate thickness and its rod are not a factor
(maybe not a bad real-world assumption just to get the area
of the opening - but different story regarding its effect on air flow which
is why Al's suggestion is a good one), I have attached a spreadsheet with
this simplification of the math.
Ed
----- Original Message -----
Sent: Saturday, September 22, 2007
12:06 PM
Subject: [FlyRotary] Re: Area of a
circle
George;
Determining the
area of the opening of a circular butterfly with position is certainly
complex enough; but the flow is likely not directly proportional because
of the complexities of the flow characteristics and pressure changes.
I would think measuring it is really the only way. Do you have
access to a flow bench?
Sorry; probably
not very helpful,
Al
G
-----Original
Message-----
From: Rotary
motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of George
Lendich
Sent: Friday,
September 21, 2007 9:21 PM
To: Rotary motors in
aircraft
Subject:
[FlyRotary] Area of a circle
I am trying to
work out the area of carb inlet as it is opened
incrementally.
This involves the
overlapped portion of two circles, as well as, a circle cut into slices (
straight cuts).
This should give
me an indication of the linier or otherwise, volume of air as it sweeps
through the carb.
This then should
indicate the shape of the grind of the needle in maintaining
continuity of the mixture ratio of fuel to air.
Any helpers with
this one!?
--
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