A one-dimensional model for supersonic ejectors based on the compound flow theory

We present a 1D ejector model based on compound flow theory and the momentum balance between two one-dimensional streams. The model reproduces the dividing streamline between the streams and the axial distribution of cross-stream averaged quantities, including momentum exchanges between the streams and the walls using friction closure laws. A formulation based on the Prandtl-Meyer relation and oblique shocks is proposed to describe the pressure equalisation between the streams, from the outlet of the primary nozzle until the pressures equalise. From that point, the compound equations including momentum exchange are integrated. The model predictions were validated against experimental data and axisymmetric RANS simulations in on- and off-design operation. The agreement confirms that the model can serve as a valuable tool for the analysis and design of ejectors, as well as its integration into complex thermodynamic cycles.