Pumps – Motor driven – Axial thrust balancing means for rotary pump and motor
Patent
1997-05-28
1999-11-23
Freay, Charles G.
Pumps
Motor driven
Axial thrust balancing means for rotary pump and motor
60 3945, F04B 1700
Patent
active
059889934
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a pressure exchanger for transfer of pressure energy from one fluid flow to another, wherein the pressure exchanger comprises a housing with an inlet and an outlet duct for each fluid flow, a rotor which is arranged for rotation about its longitudinal axis in the housing, and which has at least one through-going duct, which extends from one end of the rotor to the other end, considered in the axial direction, and alternately connects the inlet duct and the outlet duct for one fluid with the outlet duct and the inlet duct respectively of the other fluid and vice versa during the rotation of the rotor.
DESCRIPTION OF THE RELATED ART
From NO-PS 161 341 (corresponding to U.S. Pat. No. 4,887,942) and NO-PS 168 548 amongst others there are known pressure exchangers of the above-mentioned type, where the rotor is positioned by means of a shaft which is mounted in a known manner in an opposite end cover. In most applications of pressure exchangers liquids are used with low viscosity, e.g. water. Any internal leakage between areas with high and low pressure could substantially reduce efficiency, leading to cavitation at the outlet if the sealing surfaces are not functioning satisfactorily, with a severely reduced working life as a consequence. If the use of dynamic and expensive sealing bodies which reduce reliability, complicate maintenance and cause severe friction are to be avoided, the alternative is a gap or slot seal which involves production and installation while complying with extremely accurate tolerances in order to be able to employ standard precision bearing components. The latter concept also involves problems in connection with elastic deformations of housing, rotor, and end cover at higher pressure which can only be partially solved by extreme overdimensioning of components.
The above patents further indicate partition walls in the rotor ducts which have radial cross sections with straight walls or walls in the form of opposite sections of segments of a circle. The former shape is unsatisfactory with regard to fatigue in the attachment points due to elastic deformations when alternating between high and low pressure and they require to be overdimensioned. Both shapes reduce the available flow cross section and thereby the efficiency. The mixing of the liquid flows is also influenced by the ratio between available individual flow cross section and the length of the ducts. In special applications the noise level will be of vital importance and in this respect the described duct cross sections are not the most desirable.
NO-PS 161 341 describes an end cover which has inlet and outlet passages with a larger surface and pressure drop than necessary, since the flow will always be turbulent.
BRIEF SUMMARY OF THE INVENTION
The object of the invention is to provide a pressure exchanger which is not encumbered by the above-mentioned disadvantages.
The characteristics of this pressure exchanger according to the invention are indicated by the characteristic features described below and in the claims presented.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described in more detail with reference to the drawings which schematically illustrate examples of a pressure exchanger according to the invention.
FIG. 1 is a perspective view of an embodiment of a pressure exchanger according to the invention.
FIG. 2 is a perspective view of the components of the pressure exchanger illustrated in FIG. 1, but where its components are separated from one another and for some of these portions are cut away.
FIG. 3 is a diagram illustrating the forces which act on a rotor during through-flow of fluid during rotation.
FIG. 4 shows possible optimum cross section shapes for rotor ducts.
FIG. 5 is a schematic functional diagram for mounting of the rotor with straight ducts.
FIG. 6 illustrates corresponding hydrostatic pressure distribution on the rotor's surfaces during axial and radial movement from a central position.
FIG. 7 is a schematic functional diagr
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patent: 3074622 (1963-01-01), Berchtold
patent: 3234736 (1966-02-01), Spalding
patent: 4487552 (1984-12-01), Haase et al.
patent: 4887942 (1989-12-01), Hauge
patent: 5522217 (1996-06-01), Zauner
patent: 5567129 (1996-10-01), Bonardi
Evora Robert Z.
Freay Charles G.
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