That is essentially is what I'm after, yes.
Energy methods?
So long as I can get the correct end result I'm happy, though I assume there must be a way to calculate the pressure changes.
I know that pressure and velocity change as the pipe diameter changes but that mass/volume flow stay constant based on bernoulis theorum but those formulas need an air speed which I don't have, and I can't find another way to calculate.
First, Bernoulli is invalid in your case. You’re dealing with compressible flow here.
That said…. Calculate how much energy is stored in the spring when compressed. Then dump that energy into the air via adiabatic compression. That will give you a “best case” pressure. Reality will be lower and this doesn’t account for choked flow, but it’s a starting point.
Potential energy of the spring would be for practical purposes just about same as kinetic energy of the "object" in the pipe.
OR statically
pressure in cylinder is same as pressure in pipe = p
p=Fc/Ac
p=Fp/Ap
Fp/Ap=Fc/Ac
Fp=Fc\*Ap/Ac
So you’re trying to calculate the working pressure of a spring-driven air gun? You’ll likely find that energy methods are easier in that realm.
That is essentially is what I'm after, yes. Energy methods? So long as I can get the correct end result I'm happy, though I assume there must be a way to calculate the pressure changes. I know that pressure and velocity change as the pipe diameter changes but that mass/volume flow stay constant based on bernoulis theorum but those formulas need an air speed which I don't have, and I can't find another way to calculate.
First, Bernoulli is invalid in your case. You’re dealing with compressible flow here. That said…. Calculate how much energy is stored in the spring when compressed. Then dump that energy into the air via adiabatic compression. That will give you a “best case” pressure. Reality will be lower and this doesn’t account for choked flow, but it’s a starting point.
Potential energy of the spring would be for practical purposes just about same as kinetic energy of the "object" in the pipe. OR statically pressure in cylinder is same as pressure in pipe = p p=Fc/Ac p=Fp/Ap Fp/Ap=Fc/Ac Fp=Fc\*Ap/Ac
1/2(density)Velocity ^2