Owing to the complexity of the equations, these cannot be solved directly. Performance can be then calculated by considering conservation of mass, momentum and energy in the mixing tube and diffuser. However, work by Ashton, Green and Reade (1993) suggests that the use of a diverging section is not necessary for effective operation, at least at moderate pressure ratios.
An 'on-design' condition can be defined where the static pressures of primary and secondary flows are equal at the nozzle exit. In some ejector designs, a converging-diverging nozzle is utilized to accomodate the expanding jet.
(See Critical Flow, Jets and Nozzles.)ĭownstream of the nozzle, flow will expand in a series of supersonic shocks until the pressures of both streams become equal and mixing occurs. Where C D is the discharge coefficient, S TH the throat area, γ the ratio of specific heat at constant pressure to the specific heat at constant volume and R, the specific gas constant.
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