Hi, I am reviewing a pneumatic calculation. One step is to calculate how many liters of air (at normal conditions) are needed to fill up some pneumatic springs.(adsbygoogle = window.adsbygoogle || []).push({});

The calculation does the following for getting the volume to add needed (Vn) to get a predefined pressure, (liters at normal conditions):

Vn = Vnew * (pmax + p0) + Vinitial * (pmax - pmin)

OR ALSO SAYS THAT CAN BE DONE:

Vn = Vinitial * (pmax - pmin) / p0

where:

Pmax: final pressure to get (manometric in bar)

Pmin: initial pressure of the spring (manometric in bar)

P0: atmospheric pressure (absolute, 1 bar)

Vinitial: initial volume

Vnew: Increase in volume of the spring due to the pressure increment.

Vn:volume of air in normal conditions to add to the spring in order to get the final pressure.

I don´t really trust this formulae, applying Boyle I have got:

considering no volume change and manometric pressures Pmin Pmax:

Vn = Vinitial * (pmax - pmin)/(pmin + p0)

considering volume change Vnew and manometric pressures Pmin Pmax:

Vn = Vnew*(pmax+p0)/p0 + (pmax - pmin) * Vinitial / (pmin + p0)

What do you think? am I correct? or you see some logic to the original formulae that I can´t understand?

Regards

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# Volume to fill pneumatic spring at a pressure

Can you offer guidance or do you also need help?

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