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Ed,
I agree!
But having no prior experience, it gives me
something muse over at and points me in the right direction -
hopefully.
George (down under)
Yes, I've always enjoyed using math to try to get
a model for what the real world is doing. But, as I always say our Math
models are a dumbed-down representation of the real
world, so don't be surprised if you find differences between the two
(:>).
Have fun, George.
Ed
----- Original Message -----
Sent: Sunday, September 23, 2007 2:47
AM
Subject: [FlyRotary] Re: Area of a
circle
Ed,
I intend adding a notch to the square slide for
a couple of reasons, but I don't know if either reason is valid, but I can
just treat it as an add-on.
The graph seems to validate what I had done
manually today - it's all very interesting isn't it!?
George (down under)
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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