On the resistance offered to compressible flow by obstructions in series

A method is proposed for the determination of the flow characteristic of two flow restrictions in series, where an eliptical curve represents the relationship between the expansion coefficient (ratio of upstream and downstream pressures) and the reduced flow rate' for each individual obstruction. Elipse parameters are calculated for choking flow conditions of the combined system and the accuracy of the method is considered in the light of the assumptions made. (C.C.B.)