Pumps – One fluid pumped by contact or entrainment with another – Jet
Patent
1997-01-06
1998-10-13
Thorpe, Timothy
Pumps
One fluid pumped by contact or entrainment with another
Jet
417187, 417151, 239590, F04F 544
Patent
active
058203532
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention is directed to a jet pump and process for operating the jet pump with a driving nozzle from which a driving medium, especially steam, exits at supersonic speed and is mixed with a gaseous load medium.
BACKGROUND OF THE INVENTION
In jet pumps in which a high-speed jet of driving fluid exerts a suction effect on a driven or pumped fluid and, in so doing, entrains this fluid, the driving fluid imparts kinetic energy to the driven fluid by mixing of streams and by transfer of momentum so that a mixed jet of both fluids has a lower velocity at the end of the mixing process than the jet of entraining or driving fluid. The high velocity required for the driving fluid for this purpose is achieved in that pressure energy is transformed into kinetic energy in a so-called injection nozzle or driving nozzle. Finally, the remaining kinetic energy of the mixed jet is transformed into pressure energy again in a diffuser.
The driving fluid and driven fluid are chiefly gaseous media and vaporous media. The final velocity of a gaseous or vaporous driving medium is considerably greater than the speed of sound in jet pumps with high capacity and with a high pressure ratio. This is achieved by means of a cross-sectional widening in the supersonic portion of the nozzle so that potential energy is transformed into kinetic energy in conjunction with a simultaneous pressure drop. Supersonic nozzles generally have a circular cross section with a conical or contoured supersonic portion.
A steam jet pump in which the working steam is ejected from a jet nozzle widening toward the end is described in German Patent publication 3406201A 1 . The working steam achieves its critical velocity, i.e., speed of sound, when passing through the neck portion of the nozzle. Since the steam passes through the widening portion of the nozzle, the pressure energy is completely transformed into kinetic energy and the steam is ejected into a chamber at supersonic speed.
With the great differences in velocity between the load mass flow and the driving mass flow, the mixing process in high-capacity jet pumps is inefficient and slow using this known jet pump design. This results in losses in the process, particularly friction losses, and an excessively large construction length of the jet pump or incomplete mixing and accordingly output losses. It is not possible to manipulate the supersonic flow in the supersonic core jet as is possible, for example, in the subsonic region, e.g., by means of interference bodies initiating turbulence, in view of the considerable losses due to compression shocks.
The usual increase in the mixing area between the driving or primary jet and the secondary jet effected in jet engineering by means of rosette-shaped nozzles, known as hypermixing, is possible only in the subsonic region. In the hypersonic region, such a step would immediately lead to destruction of the jet momentum due to compression shocks resulting in failure of the pump.
THE SUMMARY OF THE INVENTION
The object of the present invention is to provide a jet pump and process for operating the jet pump in which an increase in the mixing of driving medium and load medium is achieved in a simple design.
This object is met by the present inventive process for operating a jet pump with a driving nozzle from which a driving medium, especially steam, exits at supersonic speed and mixes with a gaseous load medium. Downstream of an outlet of the nozzle in the mixing region the circumferential length is increased by a cross-sectional shape of the driving jet deviating from the circle in order to eliminate azimuthal symmetry of a vortex structure of the driving medium, so that the respective cross-sectional surface, in accordance with the principles of continuity, begins in a jet direction with a circular cross section in a supersonic portion of the jet corresponding to the circular cross-sectional surface of the driving medium in conventional supersonic nozzles.
In addition, the object is met by a jet pump device, especially a steam
REFERENCES:
patent: 3143293 (1964-08-01), Purse
patent: 3774846 (1973-11-01), Schurig et al.
Beylich Alfred E.
Blanke Martin
Mannesmann Aktiengesellschaft
Thorpe Timothy
Tyler Cheryl J.
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