Abstract
In this study, we proposed a method for calculating the sonic conductance of a short-tube orifice. First, we derived a formula for calculating the sonic conductance based on a continuity equation, a momentum equation and the definition of flow-rate characteristics. The flow-rate characteristics of different orifices were then measured using the upstream constant-pressure test method in ISO 6358. Based on these test data, the theoretical formula was simplified using the least squares fitting method, the accuracy of which was verified experimentally. Finally, the effects of the diameter ratio, the length-to-diameter ratio and the critical pressure ratio were analysed with reference to engineering applications, and a simplified formula was derived. We conclude that the influence of the diameter ratio is greater than that of the length-to-diameter ratio. When the length-to-diameter ratio is <5, its effect can be neglected. The critical pressure ratio has little effect on the sonic conductance of a short-tube orifice, and it can be set to 0.5 when calculating the sonic conductance in engineering applications. The formula proposed in this study is highly accurate with a mean error of <3%.
Highlights
An orifice is a sudden flow restriction of short or zero length, and it is a basic element of pneumatic components such as nozzleflapper servo valves, solenoid valves and pneumatic bearings
The problems with the existing approaches can be summarised as follows: the discharge coefficient is complex and varies with the pressure ratio, making it unsuitable for engineering applications; the sonic conductance formulae neglect the local and frictional losses in a short-tube orifice, leading to large errors, and the formulae lack a theoretical basis, making it difficult to extend them to other dimensions
When the structure of an orifice varies, these parameters will change simultaneously, and the degrees of impact will vary with different b and lengthto-diameter ratio (L/d)
Summary
An orifice is a sudden flow restriction of short or zero length (in the case of a sharp-edge orifice), and it is a basic element of pneumatic components such as nozzleflapper servo valves, solenoid valves and pneumatic bearings. Keywords Pneumatics, flow-rate characteristics, short-tube orifice, sonic conductance, critical pressure ratio Formulae have been proposed for calculating the sonic conductance of orifices.[9,10] as both were derived by fitting the experimental data, their applicability is limited.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
