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Math not working out
Posted: Sat Nov 03, 2007 8:34 pm
by sandman
Ok, im learning Visual Basic.NET now with the help of an awesome teacher
So i thought i would start out small with something like a fuel tool, it is supposed to give you the pressure that is supposed to be in your meter. Well, i used the equation shown
here and im not getting the same numbers as my stoichiometry. So i come to you with questions hoping to get answers, i will include pics to help you im assisting me.
Posted: Sat Nov 03, 2007 8:54 pm
by benstern
Thats unpossible math always works!!
Posted: Sat Nov 03, 2007 9:05 pm
by sandman
i know, so i blame windows
if the answers were close i would not be complaining but they are way off
Posted: Sat Nov 03, 2007 11:56 pm
by clide
A few things
That formula you used calculates pressure in ATM, multiply by 14.7 to get psi.
Second, I'm not sure why they subtracted 1 at the end of that thread. I would think Pm = 0.042*Vc/Vm would give you the gauge pressure needed for the meter.
Making those two changes and making the chamber 19 inches like you used in the hand calculation I get the same answer that you got.
A few things you can do to simplify the program too. Since you are doing the same calculations to the chamber and meter diameters to get the chamber and meter volume and then divide the two, those calculations cancel out and you can simply use Pm = (Dc^2*Lc*0.042)/(Dm^2*Lm)
E.G.
<a href="
http://www.google.com/search?q=.042*2.8 ... 88">Google Calculation</a>
Posted: Sun Nov 04, 2007 8:56 am
by sandman
ok, i will fix that when i get back home
thank you very much clide
i would have never thought about it giving me atmospheres
again thank you
Posted: Sun Nov 04, 2007 9:01 am
by mark.f
sandman, the equation you were looking for is in the first post, which is:
<div align="center"><img src="
http://www.markfh11q.net/MATH/derived.gif"></div>
Second, if you're dealing with gauge pressure only, (like in a fuel tool), simply .042(V<sub>c</sub>/V<sub>m</sub>) would work. I'm still fairly certain that nobody even got the
point of that thread. The whole point was simply for me to find out why you end up with gauge atmospheres when you
input absolute atmospheres. And, I figured out why.
Clide, I believe the whole reason I put -1 at the end of that thread was a simple mistake. For some reason, I must have put that there and said it's the same. I'm editing it now.
Posted: Sun Nov 04, 2007 9:03 am
by sandman
ok, i shall change that too thanks
Posted: Sun Nov 04, 2007 9:06 am
by mark.f
Wait, change what? Make sure you got what I was saying: .042(V<sub>c</sub>/V<sub>m</sub>) will work for a fuel tool, because you're not interested in absolute pressure of the meter.
Posted: Sun Nov 04, 2007 12:44 pm
by sandman
yes so i will take out the -1 that is in there now
Edit: with those changes they come within 1 PSI of each other so im happy
thanks to everyone who helped
