  We propose a 1D unsteady model for supersonic single-phase ejectors. The
model treats an ejector as a pipe network with two inputs and one output and
combines a 1D gas dynamics formulation in each `pipe' with a junction model for
entrainment and mixing. The model is calibrated and validated on experimental
data in steady-state conditions and used to analyze the choking mechanism for
the mixed flow. The model was then benchmarked against 2D URANS simulations to
predict the ejector response to a sudden change in operating conditions,
producing traveling waves. The results show that the model can correctly
predict the ejector performance and the stream-wise evolution of relevant
integral quantities (e.g. mass flow rates and momentum) in both steady and
transient conditions.
