An Ejector use steam or gas as a motive medium rather than a liquid to entrain and compress a secondary lower pressure steam or gas. They can be used anywhere a vacuum is required, a vessel needs priming, a flue gas needs exhausting or a low pressure waste gas needs compressing to a higher useable pressure.
As a rule an Ejector operates at sonic conditions with Bamford & Morris Ejectors designed to HEI standards and the two choke principle. This is where the motive gas is passed through the inlet nozzle and accelerated to critical (supersonic) velocities to create a sonic choke. The kinetic energy and pressure drop in the motive flow generates the suction pressure and by the process of impulse transfer entrains the secondary lower pressure gas. The throat diameter creates a second sonic choke which limits the achievable suction flowrate and thereby determines the achievable discharge pressure.