Prediction of expansion-tube flow conditions using a nondimensional velocity number

A simple analytical expression was derived which can be used to estimate the real gas performance of an expansion tube. This equation is called the expansion-tube equation analogous to the classical shock tube equation. This expansion-tube equation brings out clearly the various parametric dependencies of an expansion tube performance. Expansion tube performance obtained by using the present method was compared with the real-gas equilibrium expansion theory in the case of several test-gas/acceleration-gas combinations such as Air/Air, Argon/Argon, CO2/CO2 and Neon/Neon. Quantitative differences that exist between the above two methods were established.