Rotary kinetic fluid motors or pumps – Runner has spirally arranged blade or fluid passage – Extending along runner axis
Reexamination Certificate
1999-08-31
2001-11-06
Look, Edward K. (Department: 3745)
Rotary kinetic fluid motors or pumps
Runner has spirally arranged blade or fluid passage
Extending along runner axis
C415S211200, C415S221000, C416S22300B, C416S23600R
Reexamination Certificate
active
06312216
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains to turbo machines which supply or recover the energy of a multiphase fluid, and to vary the pressure thereof.
2. Description of the Prior Art
The pumping, and also the expansion of a multiphase fluid constituted by at least one liquid phase and a gaseous phase, poses a problem which is difficult to resolve.
For example, in the case of the compression of a multiphase fluid, experience shows that the performance of the classic centrifugal pumps slumps as soon as the level of gas exceeds a few percent.
The best adapted classic rotodynamic pumps do not allow gas levels of 20 to 25% to be exceeded without the rise in pressure falling considerably. The other types of pumps, such as the reciprocating displacement pumps or screw pumps, jet-effect pumps, are also limited in their uses and their energy efficiency.
Various pumping devices have been developed in the prior art in an attempt to improve the performance of the pumps working with multiphase flow.
For example, French Patents 2,333,139, 2,471,051 and 2,665,224 disclose hydraulic cells for axial or quasi-axial pumps which exhibit blading and inter-blade channel geometries for the pumping of multiphase fluids. These cells ensure both limitation of the accelerations and good homogenisation of the fluid which are essential elements for obtaining good performance with diphase flow. The pumps are composed of one or more cells of this type, mounted in successive stages on the rotating shaft.
French Patent 2,743,113 describes a device comprising blading disposed in tandem to ensure the passage of the liquid phase from the front side to the back side and to improve the mixing of the liquid and gaseous phases in the flow channels.
German Patent 2,287,288 is an example of a stator for an axial multiphase pump designed to alternate the direction of rotation of the multiphase flow between the outlet of the rotor and the inlet of the stator. Such an arrangement makes it possible to improve the mixing of the liquid and gaseous phases.
U.S. Pat. No. 5,628,616 describes impellers for a semi-radial or “mixed flow” type pump comprising openings which allow the recirculation of the gaseous and liquid phases in order to ensure their mixing.
The communication entitled “Innovative Solutions for Multiphase Pumping”, presented in June 1995 at the “Multiphase 95” 7
th
international conference discloses a counter-rotating compressor for wet gas comprising impellers turning in the opposite direction around the same axis so as to improve the mixing of the gaseous and liquid phases.
The rise in pressure in multiphase flow obtained through such devices reaches by way of example 30 to 80% of the rise in pressure which would be obtained with a monophase fluid with a density equal to the mean density of the mixture.
Obtaining good performance with a multiphase pump comes in large part from its capacity for intimately mixing the liquid and gaseous phases. However, in the current state of the art, the multiphase flow in the cells remains practically parallel with the surfaces of the blading, the housing and the hub of the hydraulic cells.
SUMMARY OF THE INVENTION
The present invention concerns a device and a method designed to improve the increase in the gains in pressure or reductions in pressure to which a multiphase fluid is subjected. The device is equipped with one or more mechanical device which improves mixing of the liquid and gaseous phases subject to the variation in pressure.
The present invention applies to all the types of rotodynamic multiphase pumps and more generally to all the multiphase hydraulic turbo machines, for example the compressors for wet gas or the multiphase turbines.
The invention improves the mixing of the different liquid and gaseous phases subjected to variation in pressure.
The invention is applied notably, but not exclusively, in the field of pumping of a multiphase fluid, for example, a diphase petroleum effluent composed of a mixture of oil and of gas and can also be applied in devices for expansion of multiphase fluids, allowing recovering of mechanical work.
The present invention concerns a device which varies the pressure of a multiphase fluid comprising at least one liquid phase and at least one gaseous phase, the device comprising at least a housing, a hub, a rotating shaft, at least one means which varies the pressure of the fluid (impeller, diffuser), at least one of said means having at least two blades (
6
i,
6
i+
1) defining a flow channel for the multiphase fluid.
The invention comprises at least one device disposed inside at least one flow channel the at least one device generating turbulent zone inside the flow channels which mixes the liquid and gaseous phases of the multiphase fluid.
The at least one device generates a single, double or even multiple helical flows inside the at least one flow channel.
The helix or helices may exhibit an angle &agr; such that the intensity of the flow satisfies a dimensionless ratio S or “swirl number”
S
=
∫
∫
u
1
(
x
u
y
-
y
u
x
)
ⅆ
x
ⅆ
y
r
max
∫
∫
u
1
2
ⅆ
x
ⅆ
y
in which u
i
is the longitudinal component of the velocity, u
x
and u
y
are its transverse components u
t
(in the plane of rotation), r
max
is the greatest value of r={square root over (x
2
+L +y
2
+L )} with a value for S lying between 0.3 and 0.8 and preferably between 0.5 and 0.75; S characterising the intensity of rotation of the flow, and more precisely being defined as the ratio of the flux of the kinetic moment of rotation to the flux of the longitudinal momentum.
The at least one device can be one or more “beads” having a helical shape and being disposed in a helix on the walls of at least one of the blades and the hub.
The beads are disposed for example inside at least one flow channel of at least one impeller and/or diffuser.
The height of a bead is for example between ⅕ and {fraction (1/10)} of the width of the flow channel or channels, the width of the flow channel or channels being defined for example by the minimum distance between two successive blades.
The device designed to impart energy to a multiphase fluid can be formed by at least one one groove in a helix formed in one of the walls at least forming a flow channel and over at least a portion of the length of the channel.
The groove or grooves have a depth for example of between {fraction (1/20)} and {fraction (1/10)} of the thickness of one of the blades forming the flow channel.
The helix is for example of variable pitch. The pitch of the helix diminishes for example in the main direction of flow of the multiphase fluid.
The groove or grooves are positioned for example in at least one impeller and/or at least one rectifier.
The device which imparts energy to a multiphase fluid comprises for example at least one of the following elements: a twisted strip, an auxiliary blade, the elements being disposed in at least one of the flow channels.
The twisted strip is disposed in the proximity of the inlet of one or more flow channels.
The present invention also concerns a method for improving the transfer of energy achieved in a device which varies the pressure of a multiphase fluid comprising at least one gaseous phase and one liquid phase, the device comprising at least one flow channel. With the method according to the invention is characterised in the fluid is passed into at least one flow channel formed by at least two devices making it possible to vary the pressure such as blades, a hub and a housing, the channel being equipped with mechanical device making it possible to generate a turbulent zone in order to increase the mixing of the liquid and gaseous phases.
At least one helical rotation can be imparted to the flow inside the channel so as to increase the mixing of the liquid and gaseous phases.
The flow is for example a single helical flow such that the ratio S of the intensity of flow calculated in at least one transverse
Antonelli Terry Stout & Kraus LLP
Institut Francais du Pe'trole
Look Edward K.
Nguyen Ninh
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