The discharge of compressed air from a cylinder has been studied experimentally. The effect of initial pressure and of orifice geometry on the expansion in the cylinder and on the transient flow through the orifice has been examined in detail.
During expansion, radial and axial temperature gradients are established which result in departures from isentropic behaviour. The state can be reproduced analytically only by using a variable polytropic index whose values are dependent on the history of the expansion.
From dimensional considerations the effects of fluid dynamical variables and of heat transfer on the transient flow have been isolated.
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