Accurate determination of the flow rate through pneumatic devices and components

is essential to the design and optimization of industrial equipment using these

components. Indeed, the complexity of current approaches remains a barrier

to their understanding, therefore, their generalization. This issue often occurs in

pneumatic power transmission and also in the compressible fluid control valves.

It is however important for all the users to be familiar with the methods used to

determinate the flow rate characteristics of the installed devices.

A theory taking into account the compressibility of the fluid was developed in

several prior works; they allow characterizing the flow through any device by

considering the choked and the unchoked flow. The methodology developed in

the literature needs at least two coefficients: critical pressure ratio and flow rate

coefficient.

From a theoretical development, and subsequent simplified theory, this publication

provides a simple method to calculate flow coefficients and the critical pressure

ratios for all pneumatic components condidered separately or as an assembly, in

compressible fluid when the flow is assumed to be adiabatic.

An exhaustive experimental study is conducted to verify the assumptions made

here and validated the theoretical results.