sonic flow in nozzle
sonic flow in nozzle
(OP)
Hi,
I am a new engineer working on a derivation for maximum flow of a gas in a nozzle.
API RP 520, Pt. I, Para. 4.3.2.1 gives the equation for max flow to be
W=C*A*P*sqrt(T/M)
I've left out the correction factors for back pressure, non-ideal flow, and compressibility of a non-ideal gas.
Now I've been able to start with a tank of initial pressure and temperature, Po and To, and get to the following equation on my own.
W=Po*A*[(M/Ru/To)(k(2/(k+1))^((k+1)/(k-1))]^1/2
M being molecular weight, and Ru the universal gas constant.
Now the term C in the first equation is given as
C=520*[(k(2/(k+1))^((k+1)/(k-1))]^1/2
which makes the first equation almost match up with mine except for the 520 term, and the universal gas constant in my equation.
My question is this. Where did this C term come from and what are its units?
After putting in 1545.35 ft*lbf/lbmol/R for Ru and converting all the units to make sure W came out in lbm/s my term for C instead of being 520 would be 0.1443
A big thank you for any help on this.
I am a new engineer working on a derivation for maximum flow of a gas in a nozzle.
API RP 520, Pt. I, Para. 4.3.2.1 gives the equation for max flow to be
W=C*A*P*sqrt(T/M)
I've left out the correction factors for back pressure, non-ideal flow, and compressibility of a non-ideal gas.
Now I've been able to start with a tank of initial pressure and temperature, Po and To, and get to the following equation on my own.
W=Po*A*[(M/Ru/To)(k(2/(k+1))^((k+1)/(k-1))]^1/2
M being molecular weight, and Ru the universal gas constant.
Now the term C in the first equation is given as
C=520*[(k(2/(k+1))^((k+1)/(k-1))]^1/2
which makes the first equation almost match up with mine except for the 520 term, and the universal gas constant in my equation.
My question is this. Where did this C term come from and what are its units?
After putting in 1545.35 ft*lbf/lbmol/R for Ru and converting all the units to make sure W came out in lbm/s my term for C instead of being 520 would be 0.1443
A big thank you for any help on this.





RE: sonic flow in nozzle
RE: sonic flow in nozzle
If you have a converging-diverging nozzle, flow will become supersonic under sufficient stagnation pressure and the Mach number can be calculated according to the area ratio of the nozzle. Flow will still be sonic at the throat, however, and therefore mass flowrate can still be calculated using Fliegner's formula (using properties at the throat).
Haf
RE: sonic flow in nozzle
Thanks a bunch for getting me back on track.
RE: sonic flow in nozzle
A link to "Fliegner's formula" is:
http://www.ijee.dit.ie/articles/999982/experime.htm
You might also want to refer to Thread# 378-31540; it is specifically concerned with transient flow, but deals with the same subject, broadly speaking.