Rotary kinetic fluid motors or pumps – Runner has spirally arranged blade or fluid passage – Extending along runner axis
Reexamination Certificate
1999-12-27
2001-08-14
Look, Edward K. (Department: 3745)
Rotary kinetic fluid motors or pumps
Runner has spirally arranged blade or fluid passage
Extending along runner axis
C415S199400, C415S228000, C416S177000, C416S189000
Reexamination Certificate
active
06273672
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to two-phase helical mixed flow impellers and to compression and expansion devices comprising this type of impellers.
The invention notably relates to the following two-phase helical mixed flow impellers:
helical axial flow impellers where the flow occurs in an essentially cylindrical shell, a subfamily of the helical mixed flow impellers (flow in a three-dimensional shell of revolution),
compression impellers (energy transfer from the rotor to the fluid), for example, such impellers as those described in patent FR-2,665,224, and expansion impellers (energy transfer from the fluid to the rotor).
In the description hereafter:
the meridian plane of an impeller refers to any plane passing through the axis of rotation,
the radial plane of an impeller refers to any plane perpendicular to the axis of rotation,
the channel of the impeller refers to the space through which the flow runs, edged with the vanes and with the inner and outer shells.
The impeller according to the invention is notably used in devices intended for compression and expansion of a mixture consisting of one or more liquid phases, of a gas phase and possibly of a solid phase.
It can be used in many fields, for example in petroleum production, geothermics, liquefaction processes (in particular liquefaction of natural gas), combined reinjection of water and acid gases, refining processes (catalytic reforming, hydrotreating: hydrocracking, hydrodesulfurization, etc).
BACKGROUND OF THE INVENTION
Single-phase compression and expansion radial (centrifugal) and mixed flow impellers are generally covered with an outer shell (cover or cap or fairing) so as to limit leak rates and recycle rates between the upper face and the lower face of the vanes and consequently to increase the impeller efficiency. These shells are generally provided, at one end thereof, with a seal (labyrinth seal for example) so as to limit leaks between the inlet and the outlet of the impeller as a result of the pressure gradient (positive in compression and negative in expansion) that appears during energy transformation.
Patent FR-2,697,870 describes the cover of vanes of compression helical axial flow impellers with a fairing itself covered on the total outer surface thereof by a seal system. The fairing has two purposes: first, it reduces the space between the rotor and the stator, considering the vane height reductions from the first to the last stage (volume flow rate reduction), second, it reduces leaks in the vicinity of each impeller while preventing friction losses by using a suitable seal system, for example grooves arranged in the direction of rotation.
SUMMARY OF THE INVENTION
The idea of the present invention is to place an additional element referred to as “cover” on the outer part of the vanes, which has, at least at one of its ends, a slope whose value is selected so as to limit leaks between the inlet and the outlet of the impeller.
The slope of the cover end where the pressure is the highest is notably so defined that there is a balance between the pressure force and the tangential component of the centrifugal force exerted on either side on a liquid mass M trapped between the cover and the stationary part.
The specific shape of the cover notably allows to obtain at least one of the following results:
totally suppress the leak rate between the intrados and the extrados of the vanes of an impeller, and
limit the leak rate outside the cover (from the outlet to the inlet in case of compression and from the inlet to the outlet in case of expansion), thus allowing to increase the efficiency of the stage.
The invention also consists in giving a specific shape to the mean curvature of the fluid flow channel in order to limit separation of the phases of the fluid.
The invention relates to a compression or expansion two-phase helical mixed flow impeller comprising one or more vanes mounted on a boss, a cover mounted on the outer part of the vanes, the assembly being placed in a housing. It is characterized in that the cover has, at least at one of its ends corresponding to the inlet and/or to the outlet of the impeller, a slope whose value is determined so as to limit leaks between the inlet and the outlet of the impeller.
The value of the slope(s) is so determined for example that there is a balance between the pressure force and the tangential component of the centrifugal force exerted on either side on a liquid mass trapped between the cover and the stationary part.
The value of the slope can be determined by means of a length Lz, said length Lz being at most equal to a maximum length Lmax.
This value Lmax is for example at most equal to about 20% of the axial length Lt.
According to an embodiment variant, the slope is situated at the high-pressure end of the impeller (the part of the impeller with the highest pressure).
The impeller can be a compression impeller or an expansion impeller.
The compression impeller or the expansion impeller can comprise at least one flow channel delimited by at least one boss and two successive vanes, said impeller having an axial length Lt and an mean radius of curvature Rh(z), taken in the meridian plane, said radius of curvature Rh(z) being suited, over at least part of length Lt, to limit separation of the phases of said multiphase fluid in the flow channel.
The invention also relates to a compression or expansion device for a multiphase fluid comprising at least one liquid phase and a gas phase, the device comprising a housing, one or more compression cells (Ii, Ri), the impellers being mounted on a shaft, an inlet allowing introduction of the multiphase fluid and an outlet for extracting the multiphase fluid that has gained a certain energy. The compressor is characterized in that at least one of the compression cells comprises an impeller as described above.
The compression impeller or device according to the invention is notably applied for petroleum effluent pumping.
REFERENCES:
patent: 4097186 (1978-06-01), Budris
patent: 5100295 (1992-03-01), Madden
patent: 5997242 (1999-12-01), Hecker et al.
patent: 781929 (1997-07-01), None
patent: 856665 (1998-08-01), None
patent: 2333139 (1977-06-01), None
patent: 2665224 (1992-01-01), None
patent: 2697870 (1994-05-01), None
patent: 2066898 (1981-07-01), None
Antonelli Terry Stout & Kraus LLP
Institut Francais du Pe'trole
Look Edward K.
Nguyen Ninh
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