Vacuum ejector with tripped diverging exit flow

A multi-stage ejector for generating a vacuum from a source of pressurized fluid by passing said pressurized fluid through a series of nozzles, accelerating said pressurized fluid, and entraining air or other medium so as to form a jet flow in two or more stages, the multi-stage ejector comprising:

• an inlet in fluid communication with the source of pressurized fluid;
• a drive stage;
• a final stage;
• and
• two or more suction ports, wherein:
• the inlet, the drive stage, the final stage, and the two or more suction ports are arranged about an axis of symmetry, and
• the vacuum is generated across each of the drive stage and the final stage before ejecting said jet flow from the multi-stage ejector, the final stage including an ejector outlet formed as a nozzle extending to an outlet end of the multi-stage ejector, said ejector outlet nozzle arranged to receive the jet flow from the final stage of the multi-stage ejector, said ejector outlet nozzle including:
• a first diverging section extending from an inlet end to an outlet end of the first diverging section, the first diverging section extending at a first constant angle of divergence to a direction of fluid flow,
• a second diverging section extending from an inlet end to an outlet end of the second diverging section, the second diverging section extending at a second constant angle of divergence and terminating at the outlet end of the multi-stage ejector;
• and
• a stepwise expansion section extending from the outlet end of the first diverging section to the inlet end of the second diverging section, the outlet end of the first diverging section being downstream of the inlet end of the second diverging section, the stepwise expansion section providing a stepwise expansion in a cross-sectional flow area, as viewed in a direction perpendicular to a direction of the jet flow through the ejector outlet nozzle, wherein a ratio of an inner diameter immediately before the stepwise expansion section to immediately after the stepwise expansion section is between 6:7 and 20:21.