A method of operating a jet pump and a jet pump itself

A process is disclosed for operating a jet pump with an ejection nozzle that ejects an entrainment medium, in particular steam, at an ultrasonic speed, for mixing it with a gaseous load medium. In order to eliminate the azimuthal symmetry of the whirling structure of the entrainment medium in the mixing area located downstream of the outlet of the nozzle, the circumferential length of the entrainment jet is increased by giving to its cross-section a form other than circular. According to the continuity principle, the cross sectional area beginning in the ejection direction with a circular cross-section corresponds, in the ultrasonic part of the jet, to the circular cross-sectional area of the entrainment medium in conventional ultrasonic nozzles. Also disclosed is a jet pump, in particular a steam jet pump, with an ejection nozzle that expands from its neck to its end and that is surrounded by a coaxial mixing chamber to which a tapering diffuser part is connected. This jet pump for carrying out the process described in the first claim is characterised in that the cross-section of the expanding part (13) of the ejection nozzle (10) is formed by the neck (12) having a circular cross-section (Ak) with a corresponding circumferential length (LK), said neck (12) being a part of the ultrasonic part downstream of the jet. When the cross-sectional area (A) is given, the circumferential length (Lx) is larger than that obtained with the circular form. At least three projecting beads (18) that extend in the direction of the jet are shaped in the envelope (19) of the ejection nozzle.