FR2665224A1 - PUMPING OR POLYPHASE COMPRESSION DEVICE AND USE THEREOF. - Google Patents

Abstract

The present invention relates to a device for compressing a multiphase fluid comprising a liquid phase and a gas phase, and its use. The device comprises a housing (1), an impeller having an input section and an output section, said impeller comprising a hub having an axial symmetry (28) of axis Ox and a number n blades rotating about said axis, these blades having a leading edge (C1; C2) and a trailing edge (C'1; C'2) said fluid enters said impeller through the inlet section (41) and leaves it through the outlet section ( 42), said axis being oriented in the direction of progression of said fluid, the number of rotating blades (29, 30) being equal to or greater than 2. - It is characterized in that it comprises at least one channel or passage defined by two successive blades (29, 30) whose orthoradial section S (x) is of the form, to within 5% and preferably to within 3%: (CF DRAWING IN BOPI) over at least a portion of its length, said portion being between two orthoradial planes, the variable x corresponding to the abscissa along said axis whose origin corresponds substantially to the radial plane passing through the leading edge of said blades, said radial planes defining said portion having x1 and x2 as abscissa, a, b, c and d being parameters. - Application to multiphase pumping of petroleum effluent.

Description

1 - The present invention relates to a device for the pumping of

  multiphasic fluids which, before pumping and under the conditions of pressure and temperature considered, consist of the mixture including a liquid and a gas undissolved in the liquid, this liquid may or may not be saturated with gas. The pumping of a multiphasic fluid, for example, but not exclusively, a disphasic oil effluent composed of a mixture of oil and gas, raises problems that are all the more difficult to solve in the thermodynamic conditions of the two-phase fluid. before pumping, the value of the volumetric ratio of the gas at

liquid is larger.

  It is recalled that the volumetric ratio of gas and liquid, which will be called later abbreviated "volumetric ratio" or GLR (of the English "Gas Liquid Ratio"), is defined as the ratio of the volume of fluid to the gaseous state to the fluid volume in the liquid state, the value of this ratio depending on the

  thermodynamic conditions of the two-phase fluid -

  Whatever the design of the pumps used (alternative pumps, rotary pumps or trumpet pumps), good results are obtained when the value of the volumetric ratio is zero, because the fluid then behaves like a liquid monophasic fluid These materials are still usable when their operating conditions do not reveal phenomena likely to allow the vaporization of a large part of the gas dissolved in the liquid, or when the value of the ratio

  volumetric at the inlet of the pump is at most 0.2.

  Experience shows that beyond this value, the efficiency of these devices decreases very quickly and they are practically usable. 2 - To improve the operation of existing equipment, the gaseous phase is separated from the liquid phase before pumping and each is treated separately in separate pumping circuits The implementation of separate circuits is not always possible and anyway, complicates the pumping operations. Therefore, attempts have been made to develop pumping devices adapted not only to increase the total energy of the two-phase fluid, but which can produce a two-phase fluid whose volumetric ratio at the output of the device has a lower value than

fluid before pumping.

  Thus, several impeller blading profiles have been described for example in the French patent applications.

2,157,437, 2,333,139 and 2,471,501.

  The device according to the invention is referred to as a compression cell, it can also be called a compression pumping cell since it is suitable for liquids as well as liquid gas mixtures or gases. to call him

compression cell.

  The present invention relates to a device which uses particular blades, blades or fins to increase the pumping efficiency of disphasic fluids whose volumetric ratios are higher than those of the prior art. In particular, the device according to the present invention allows to treat multiphase fluids whatever the GLR with a compression efficiency which can be greater than 40% or 50% in

  the most unfavorable operating domain.

  A compression cell generally comprises two parts: an impeller and a diffuser The impeller is of two elements, the fundamental element The impeller is normally mounted on a rotating shaft, keyed or shrunk on this shaft The diffuser is static and integral with the body of the machine The series assembly of several of these cells constitutes the hydraulic cell of a pump. According to the conventional rules for the construction of rotating machines, the shaft is supported in two or more points by bearings integral with the mechanical pivots included in the body of the machine.

  pump The pump has suction and discharge.

  The compression cells may be identical or

different dimensions.

  Compression cells are basically defined

by their geometries.

  The present invention relates to a device for compressing a multiphase fluid comprising a liquid phase and a gaseous phase, this device comprising a housing, an impeller having an inlet section and an outlet section, said impeller comprising an axysymmetric hub. (having axial symmetry) Ox axis and a number N of blades rotating about said axis, said blades having a leading edge and a trailing edge Said fluid enters said impeller by the inlet section and leaves by the exit section, said axis being oriented in the direction of progression of said

  fluid, the number of rotating fins being equal to or greater than 2.

  The device according to the invention is characterized in that it comprises at least one channel or passage defined by two successive blades whose orthoradial S (x) section is of the shape, to 5% and preferably less than 3% near:

2 2 /

  S (x) = ax + b (cx 2) 1/2 + d over at least a portion of its length, said portion being between two orthoradial planes, the variable x corresponding to the abscissa along said axis whose origin corresponds substantially to the radial plane passing through the leading edge of said fins, said radial planes defining said portion having for abscissa x 1 and x 2,

  a, b, c and d being parameters.

The value a may be equal to:

a = x 7.

n 4 - t = 3.141 and

  n being equal to the number of blades of the impeller.

  The values of b and c may be equal to 5.b = 1 2 M + e let c = A = (M R 1) 2 o 1 2 2 R 2

3 1

M =

2 (R R 1)

  n number of impeller blades, e: blade thickness, B: rope angle, c L: axial length of the blades, R 1: minimum radius of the blades at the inlet, R 2: maximum radius of the blades at entry,

  R 3: minimum radius of the blades at the exit.

  The value d may be equal to: 1 e d = R 2 M) ((R 2 + M) + - (M -R 1 n sin B c The blades may have upper edges registering

  in a cylinder of revolution whose axis of symmetry axis Ox.

  The portion of the canal may correspond to the entire length

of the canal.

  The angles of entry of the blades are for the intrados angles between 4 and 24 and preferably between 4 and 12, and for the extrados angles between 2 and 23 and preferably between 2 and 11. o The hollow of the blades defined as

B M B M

  BM-BM s e may be between 0 and 30 and preferably between 6 and 12, B M being the mean exit angle of the blade and B M the average angle

entrance to the blade.

entrance to the blade.

  - The average thickness of the blade is between 3 and 5 mm

  outside the neighboring areas of the leading and trailing edges.

  The number of blades can be between 3 and 8, and

  preferably between 4 and 6, terminals included.

  The blades may have an intrados exit angle of between 4 and 54 and preferably between 10 o and 24, and for

  the extrados angle 2 to 58 and preferably 80 to 230.

  The average profile or skeleton of said blades defined by the intersection of a blade of zero thickness and a cylindrical surface relative to said axis may be such that the angle formed by this profile with said axis decreases monotonously from the edge of attack towards the trailing edge and the curve representing the value of the curvature along the profile of the blade as a function of the curvilinear abscissa to a slope whose value increases from the edge

  of attack towards the trailing edge of the blade.

  Said curve may have a point of inflection.

  The device according to the invention may comprise a

diffuser with blades.

  This diffuser may have between 8 and 30 blades and

preferably between 15 and 25 blades.

  The axial length of the impeller relative to its external diameter may be between 0.10 and 0.40 and preferably

between 0.15 and 0.20.

  The hub of the diffuser may have a shape of revolution around the axis Ox, and the line considered in an axial plane generating this form of revolution may have at least one

inflection point.

  This line may have tangents parallel to said axis at both ends of this line corresponding to the input and

output of the diffuser.

  The present invention also relates to the use of at least one device described above, in the construction of a multiphase pump and the use of such a multiphase pump for carrying out multiphase effluent pumping operations. oil. All the advantages of the device according to the invention, which is of simple, robust and economically profitable design, will appear

  upon reading the following description, illustrated by the figures

  appended among which: Figure 1 shows schematically and in axial section, a particular embodiment of a pump using the device according to the invention for pumping, a two-phase effluent, Figure 2 shows an impeller, seen in perspective 3 is a sectional view of an impeller which has been shown to be a blade, FIG. 4 is a developed view of the trace resulting from the intersection of blades with a cylindrical surface. FIGS. 5 and 6 respectively show the detail of FIG. leading and trailing edge of a blade, FIG. 7 shows the evolution of the section of a passage as a function of the axial abscissa, FIGS. 8 and 9 represent a rectifier, and FIG. embodiment of a blade or dawn

of the rectifier.

  In what follows, the term "fluid" is a single-phase gas or exclusively liquid fluid in which a gas is totally dissolved, or a multiphase fluid including in particular a liquid phase and a gas phase and possibly solid particles for example of sand or viscous particles such as agglomerates hydrates The liquid phase can obviously be made of liquids of different natures, likewise, the phase

  gas can be made of several gases of different natures.

  FIG. 1 represents schematically and in axial section a particular, non-limiting embodiment of a pump assembly using the device according to the invention.

  intended for pumping a multiphase petroleum effluent.

  In an example of FIG. 1 between the intake and discharge openings 3 of the pumping device and inside the casing 1, at least one compression cell according to the invention is placed. increase the total energy of the fluid In Figure 1, three impellers referenced 17 to 19 are visible This number is not limiting and depends on the pressure increase that is desired. These elements, which will be described in more detail below, are integral with the shaft 6 on which they are, for example, force-fitted, the spacing between the elements being maintained by

spacers 20 to 23.

  Preferably, a diffuser or rectifier such as the diffusers 24 to 26, is placed at the outlet of each impeller, this diffuser being integral with the casing 1, for example, by means of

  fixation 27 (symbolized by mixed lines in the figure).

  Each pair of impulse and diffuser (17, 24; 19, 26)

  constitutes with a portion of the casing a compression cell.

  Reference 14 designates a deflector.

  For the clarity of Figure 1, the clearance between the spacers and the diffusers, the games between the impellers and the casing and the games between the impellers and the diffusers have been considerably increased, but it must be understood that these games are reduced to their limits. minimum value compatible with the mechanical operation of the pump, so that the fluid leaks are minimal and that, at the operating temperature, the expansions of the various components of the pumping device do not cause any

jamming.

  FIG. 2 diagrammatically shows, in perspective, a nonlimiting embodiment of an impeller element or stage essentially comprising a hub 28 integral with the shaft 6 which, during the operation of the device, is rotated in the indicated direction by the arrow r 'Two blades 29 and 30 have been shown in Figure 2, but this number is not limiting In general, we choose a number of blades to facilitate the static and dynamic balancing of the rotor The blade height is such that the shape they delimit during their rotation is 8 - complementary to the bore of the casing 1 which, in the illustrated example,

is cylindrical.

  These blades can be reported and fixed by welding to the hub 28, but it is preferable to make the assembly, hub and blades, by molding or milling.

  The impeller and the rectifier are of the helicoaxial type.

  FIG. 3 defines the dimensions of an impeller according to the invention. This figure is diagrammatic, only the hub is in section,

  and the trace t of a blade has been represented.

  R 2: is the outer radius of the impeller and therefore of the cell.

  D 2: 2 R 2 is the outside diameter of the impu Lseur, it is the diameter

nominal value frequently used.

  R 1: is the radius of the input side side hub, on the left in figure 3. R 3: is the radius of the output side side hub, right in figure 1. I: is the length along the axis of the impeller is the distance

  between the entrance face and the exit face.

  P 1 P 2: P 1 P 2 represents the curve corresponding to the intersection of the

  hub with an axial plane passing through the axis of rotation Ox.

  Ox: is the axis of rotation, where O is the point on the intersection axis

  with the input face defined above.

  in Pl: the tangent to the curve P 1 P 2 at the point P1 is perpendicular to

  the input face so this tangent is parallel to the Ox axis.

  The hatched portion of Figure 3 corresponds to the axisymmetric hub.

  Figure 4 defines the blades of the impeller.

  On the hub previously described are wound blades;

  the number of blades N is preferably always greater than or equal to 2.

  The number may be between 3 and 8 and preferably between 4 and 6, especially for impellers whose outside diameter of the blades

varies between 100 and 400 mm.

  The simplest representation to describe the blade is to define its geometric layout on the developed surface of 9 - the cylindrical envelope to the outer radius r, r can be understood

  between R 3 and R 2 This surface is represented in the plane (FIG. 4).

  It contains: the trace C 1 C 2 of the input face represented by a straight line 41, the trace C 'C' of the output face represented by a line 42. I 12 The two straight traces 41, C 1 C 2 and right 42 C'I 1 C 'are 12 i 2 parallele and distant from L called (above) length of

the impu Lseur.

  This figure shows the trace of the axis Ox, axis of rotation which is oriented in the direction from the inlet face to the exit face La F 'F' designates the direction of progression of the blades. The blades are integral with the hub They are

  geometrically defined in the following manner.

  Each blade has two faces, a lower face 31 and an extrados face 32, a leading edge or point C 1 (or point C 2), a trailing edge at point C'1 (or point C'2) , and a thickness

  defined as the distance between the intrados and the extrados.

  The angles of the blades are defined in the following manner (see FIGS. 5 and 6): The ang The intrados entry Be I: ang The of the tangent in C (or C 2) to e 1 2

  the intrados with the trace 41 of the face of entrance.

  The angle of entry extrados Be E: angle of the tangent in 'C 1 (or C 2) to

  the extrados with the trace of the face of entrance.

  The intrados exit angle B I and the extrados outlet angle S extrados B E are defined in the same manner with respect to the points S

  C 'and C' and the trace 42 of the exit face.

1 2

  We then define the chord angle Bc, as for any profile, it is the angle of the chord C 1 C'1 or C 2 C'2, lines joining points C 1 and C'1 on the one hand (or C 2 and C'2) and the trace or the exit face These different angles are defined from a

  parallel direction to the right 41 or 42.

  In Figure 6 the chord is confused with the profile of

  the intrados near the trailing edge.

  - The length of the rope C 1 C'1 is then equal to the value

  L / sin Bc, L and Bc as defined above.

  Let N be the number of blades, the relation length C 1 C 2 = 27 XR 2 / n defines the orthoradial distance, that is to say in a plane perpendicular to the axis Ox, between two blades. The shape of the blade proper is defined by the

  traces of the intrados and extrados in this plane of Figure 4.

  The curve of the intrados connecting C 1 to C 1 can be defined by a second degree equation as a function of the curvilinear abscissa of the blade counted from C 1; this curve is tangent to the trace of the angle Be I or point C 1 and to the trace of the angle Bs I at the point C'1. The curve of the extrados connecting C 1 to C'1 can be defined by a fourth degree equation as a function of the curvilinear abscissa of the blade, counted from C 1, this curve has a tangent forming an angle Be E in the neighborhood of C 1 and Bs E at

neighborhood of C'1.

  The skeleton of the blade or medium fiber of the blade can

  be represented by a fourth degree equation.

  The radius of curvature Pm of the blades are also defined according to the curvilinear abscissa. Thus the curvatures are defined.

  1 / pm and especially the average fiber curvature.

  Finally, we define the curvature variation curve as a function of the curvilinear abscissa of the average fiber called d (l / pm) ds. The curve d (1 / pm) / ds is an increasing and continuously increasing curve with a point d inflection We will be able to use

  the skeleton form described in French Patent FR 2,333,139.

  The thickness of the blades is small (practically between three and five millimeters, for certain particular industrial applications the blades may be of greater thickness) in the case where the thickness of the blade is not constant or can not be considered as such it will be possible to use in the formulas that follow either the actual thickness of the blade as a function of the abscissa or use a fixed value for the thickness of the blade, this 11 - thickness may be equal to the thickness blade average The blades are generally thinner on the leading edges and on the trailing edges. In current technology, for leading and trailing edges, shapes are allowed, the trace of which in the plane of FIG. are half circles of radius of the order of 1 mm (min.

0.5 mm, maximum 2.5 mm).

  The hollow of the blades is defined as the difference of the mean angles (or the average fiber) of output Bs M and of input Be M, more precisely BE and BI being defined at the output, we have S s BM (BE + BI) / 2 in the first order If the accuracy is a few percent; in the same way we have:

B M X (B I + B E) / 2

  ee e The hollow defined as the difference B M B M is one of the s e

  characteristics of these impellers.

  It is preferably between 6 and 120 degrees but

  its values can cover the 0-30 domain in some cases.

  The entry angles are also preferably chosen between limited values: Be I: between 40 and 240, preferably 40 to 12 e BE: between 2 and 230, preferably between 2 and 11 O e The orthoradial distance between the blades is defined as being the distance between a point of a lower surface and a point of the extrados of the previous blade measured in an orthoradial plane perpendicular to the Ox axis (Figure 4) (ie perpendicular to the plane of Figure 4). always this distance on the cylindrical surfaces Ox axis and always parameterized as a function of r radius of the cylinder reference 33, r (see Figure 2) is always smaller than R 2 nominal radius but can go up to values very close to R 2. -12 - In the strict geometrical sense and also in the technological and physical sense, this orthoradial distance is equal for any orthoradial plane of abscissa x (counted on Ox) to the value in any point M 27 Cr / ne / sin ( B Mcour) Mcour r: radius of the cylinder reference n: number of impeller blades e: blade thickness B Mcour: angle of the skeleton or the average fiber for a current point designated "yard" This distance is also geometrically equal, for industrial practical achievements at the orthoradial distance between two positioned blades such that the average fibers would be confused with the rope of the blade, so we also have: distance = 27 tr / ne / sin B c A helicoaxial pump is defined as all the pumps

  or all compressors by its volumetric flow or nominal flow.

  The input and output sections of the impeller can be determined in particular from velocity triangles by applying among others the laws of Euler in relation to the

  desired operating conditions.

  The orthoradial section defines the hydraulic channel.

  For the impeller object of this invention is defined the evolution of the section of the hydraulic channel or this orthoradial section of the channel possibly taking into account the radial thickness of the blades This sectional evolution takes into account the following geometrical parameters (defined below). before): -R 2, R 1, R 3, l N: number of blades B: the chord angle e: th 'thickness of a pae, as it has been said previously, this e: the thickness of the pale, as mentioned above, this 13-

  thickness can be assumed to be zero, constant or non-constant.

  In the case where the thickness of the blade is assumed to be zero or constant when it is not really it will be necessary to admit practical deviations from the formulations proposed above. The section is defined with respect to x current point on Ox, it can be defined also according to the curvilinear abscissa

of the rope of the profile of the blade.

  The parameters used in the formulation are written: M = 1 2 + (R 32 R 12) 1/2 (R 3 R 1 A = (MR 1) 2 = 1 L 2 + (R 3 R 1) 23 2 / l 2 (R 3 R 1) 2

B = R 2 M 2 A

  The section of the hydraulic channel 51 for a theoretical blade of zero thickness is written: 51 (x) = (7 C / n) 1 x 2 + 2 M (Ax 2) 1/2 Bl The orthoradial section of a blade 52 is written: 52 (x) = 32 M - (A x 2) 1/2 l (e / sin Bl The real orthoradial section of a hydraulic channel S is written as: S (x) = 51 (x) 52 (x) so S (x) = (1 / n) FlZx 2 + (A x 2) 1/2 (2 ZM + e / sin Bc) + (R 2 M) (7 t (R 2 + M) + e / sin B) (MR 1) 2 l 14 - In the case where all the channels are not identical we can consider N not as the number of blades but as a

  parameter related to the relative input section of each channel.

  The formulation according to the curvilinear abscissa of a current point on the chord of the profile is written simply by replacing

  x by s / sin B o S is the curvilinear abscissa.

  According to the present invention, the orthoradial section of at least one passage evolves in the manner indicated by the formula giving S (x). Nevertheless deviations from this formula may be less than 5% or preferably less than 3% and this between two orthoradial planes of abscissa X 1, x 2 (see Figure 7) Of course it is preferable that the section of a channel given by the formula above is best respected, especially given the tolerances

Manufacturing.

  The distance X 1, x 2 of the axis Ox for which the formula giving the variation of the orthoradial section is verified under the precision conditions already indicated above, is equal to at least 80% of the length of the impeller and of superior preference

at 90%.

  Due to the taper of the blades at the leading edge and the trailing edge we can admit, when it is desired that the formulas giving the variation of the orthoradial section are verified at best, and on the greatest possible length of the hub, that they are not all the same over a certain length of the blade at the two ends of these These lengths, corresponding to tears of the blade, can be determined according to the difference of the thickness counted as a percentage of the maximum thickness (generally located in the middle of the length of the developed blade or at the average thickness of the blade) Hereinafter are given these lengths referred to the curvilinear abscissa of the skeleton counted from the curvilinear abscissa Ir a) Lr = 3% from the leading edge o the length necessary for the thickness of the blade to reach more than 50% of the average thickness, - b) L = 3% before the edge of leak o the length from the which r the thickness of the blade is less than 50% of the average thickness. According to the present invention the ratio between the length of impu Lseur to its outside diameter can be between 10 Z and

  % and preferably between 15% and 25%.

  At the outlet of a impure stage, the fluid is driven by a speed having at least one axial component and a circumferential component. As is well known to those skilled in the art, the use of a rectifier makes it possible to increase the static pressure. by removing or at least reducing the circumferential component of the fluid flow velocity This rectifier can be of any known type, with characteristics adapted to those of the impulse stage, as indicated below with reference to the

Figures 8 and 9.

  FIG. 8 shows, in section, an assembly comprising an impulse (shown in broken lines) and a straightener

(shown in solid line).

  FIG. 9 schematically represents the developed trace of the intersection of a fin of the straightener with a surface

cylindrical of radius r.

  The rectifier consists of a sleeve 34 which carries at least two fins 35 A ring 36 fixed on the fins 35 allows the joining of the rectifier and the casing 1, for example Emple by means of

screws schematized in 27.

  The outer diameter of the sleeve 34 decreases progressively from the inlet to the outlet on a first portion M'N 'which can represent at least 30% of the total length of the rectifier measured parallel to the axis and which, it is equal to less than 30% of the mean diameter Dm of the blades at the inlet of the straightener Thus, the fluid passage section increases according to a law of the first or second degree when considering the direction of flow indicated by

the arrows.

  The fins 35 have a suitable profile which allows the straightening of the flow of the fluid at the inlet of the straightener, this profi L is substantially tangent to the flow while at the end of the first portion. 'N', the profile of the fins is substantially tangent to a plane passing through the axis of the device, the angle

  tilt gradually varying on this first portion.

  In order to simplify the manufacture of the straightener, the first portion M'N 'of the fins is given a constant radius of curvature. The remaining portion N'P 'of the fin is arranged

  axia Lement and on this part, the hub is cylindrical.

  The input cross-section of a rectifier S is chosen greater than the output section Ss of the preceding impulse stage. The rectifier such that the ratio S e / SS can have a value between 1 and 1, 2 and, preferably, between 1.1 and 1.15, while the ratio s / Se between the straight sections between the output and the inlet of the rectifier is greater than 1 and, preferably, included

between 2 and 3.

  In the foregoing, there is shown a weak axial clearance L between the trailing edge of the impeller blades and the leading edge of the straightener blades, but it is possible to discard them. other at a distance to be determined by the technician During the development tests according to the conditions of use of the device. Modifications may be made without departing from the scope of the present invention For example, and as shown in Figure 10, the upper surface of each fin of the rectifier may

  be obtained by machining portions of secant planes.

  Advantageously, the sleeve may be constituted by a form of revolution obtained by the rotation of a plane line 36 M ', T', N ', P' around the axis Ox of the compression cell, this line comprising at least two parts A first part M'T 'corresponds to an arc whose center is on the same side as the axis Ox relative to this line A second part T' and N '17 - also corresponds to an arc of circle preferably of same radius as the first arc M'T 'but whose center is located on the other side

  of said line relative to the center of the circle of the first arc M'T '.

  The two arcs of circle M'T 'and T'N' are interconnected at T 'with preferably parallel tangents at this point o, in this case T' is a point of inflection of the curve M'T ' N 'The orthogonal projection on the axis Ox of the arc M'T' may be equal to

  the corresponding length is of the arc T'N 'or of the curve T'P'.

  The tangents to the line M'T'N'P 'at M' and P 'may be parallel to the axis Ox possibly comprise a third part N'P' rectilinear parallel to the axis Ox The line M'T'N 'P' described

  previously was in an axial plane of the compression cell.

  The length of the impeller and the diffuser may be equal. In FIG. 7, two curves are shown that correspond to the variation of the orthoradial section of an impeller channel as a function of the abscissa on the Ox axis. The origin of this axis corresponds to the input face of the the impeller, this face having the leading edge of the leading edge relative to the

the flow of gases.

  This part of this curve 37 extends to the abscissa I corresponding to the length of the impeller, the abscissae x 1 and x 2 defeat the area X 1, x 2 within which the formulation given previously for the variation of the orthoradial section S (x) is respected under the conditions of precision already

  previously indicated in this text.

  XI may be equal to l-x 2 The length x 1 may correspond to the length for which the thickness of the blade has reached 80 or 90% of the average thickness Generally this length may correspond to 3% of the

length of the curvilinear abscissa.

  Similarly x 2 can be determined as the beginning of the zone x 2, where the thickness of the blade deviates by more than 10% or 20%

of average thickness.

18 -

  The tangent 38 to the curve 37 in S can be horizontal.

  e In Figure 7 the tangent 39 to the curve at the point

abscissa L has a negative slope.

  Curve 43 corresponds to the evolution of the orthoradial section of a diffuser channel multiplied by nr / ni where n R corresponds to the number of blades or fins of the diffuser and n I the number

  blades or fins of the impeller.

  Curve 43 is a continuous curve between abscissa 1 and L 3 and has no singular point.

inflection point 44.

  Preferably the abscissa of this point of inflection can be

substantially equal to (l + 13) / 2.

  The tangent 45 at the inlet of the diffuser corresponding to the abscissa 1 to the clearance between impeller and diffuser is the horizontal (L d parallel to the axis Ox) It is the same at the exit of the

  diffsueur the tangent 46 is parallel to the Ox axis.

  The length L 3-L corresponds to the axial length of the diffuser. Preferably the output section S of the impeller channel will be strictly equal to the input section in the diffuser.

_- 2665224

19 -

Claims (18)

R E V E N D I C A T IO N S   A device for compressing a multiphase fluid comprising a liquid phase and a gaseous phase, said device comprising a housing (1), an impulse having an inlet section and an outlet section, said impeller (17; ) having a hub and a number N blades rotating about said axis, said blades having a leading edge (C 1; C 2) and a trailing edge (C'1; C'2) said fluid enters said impeller by the inlet section (41) and exits therefrom through the outlet section (42), said axis being oriented in the advancing direction of said fluid, the number of rotating blades (29, 30) being equal to or greater than 2, characterized in that it comprises at least one channel or passage defined by two successive blades (29, 30) whose orthoradial section S (x) is of the form, within 5% and preferably within 3%: S (x) = ax 2 + b (cx 2) 1/2 + d over at least a portion of its length, said portion being between two orthoradial planes, the variab the x corresponding to the abscissa along said axis whose origin substantially corresponds to the radial plane passing through the leading edge of said blades, said radial planes defining said portion having for abscissa x 1 and x 2,   a, b, c and d being parameters.   2 Device according to claim 1, characterized in that a = 7 C / n o: = 3,141 and   n being equal to the number of blades of the impeller.   3 Device according to one of the preceding claims,   characterized in that: - b = (1 / n) l 27 UM + e / sin Bc I and c = A = (MR) o M = (12 + R 32 R 1) / l 2 (RR n: number of impeller blades, e: blade thickness, B: chord angle, cl: axial length of the blades, R 1: minimum radius of the blades at the inlet, R 2: maximum radius of the blades at the inlet,   R 3: minimum radius of the blades at the exit.   4 Device according to one of the preceding claims,   characterized in that d = (1 / n) (R 2 M) (75 (R 2 + M) + e / sin Bc) (MR 1) 2 l the definitions of n, e, B c LR 1, R 2 and R 3 correspond to those data in claim 3.   Device according to one of the preceding claims,   characterized in that said blade has an upper edge forming a cylinder of revolution having as axis of symmetry said Ox axis.   Device according to one of Claims 1 to 5,   characterized in that said portion of said channel corresponds to the entire length of said channel.   7 Device according to one of claims 1 to 5,   characterized in that said portion of the channel corresponds to a length of at least 80% of the length of the impeller or   preferably at least 90% of this same length.   8 Device according to one of the preceding claims,   characterized in that the inlet angles of the blades are for the 21 inside angles between 40 and 240 and preferably between 40 and, and for the ang extrados between 20 and 230 and o o preferably between 2 and 11   9 Device according to one of the preceding claims,   characterized in that the trough of the blades is between 00 and 300 and preferably between 60 and 120.   Device according to one of the claims   previous, characterized in that the average thickness of the blade is between 3 and 5 mm outside the neighboring areas of the edges attack and flight.   11 Device according to one of the claims   preceding, characterized in that the number of blades is included   between 3 and 8, and preferably between 4 and 6 inclusive.   12 Device according to one of the claims   preceding, characterized in that said blades have an intrados exit angle of between 40 and 540 and preferably between 100   and 240, and for the extrados angle 20 to 580 and 80 to 230.   13 Device according to one of the claims   previous, characterized in that the average profile or skeleton of said blades defined by the intersection of a blade of zero thickness and a cylindrical surface relative to said axis, is such that the angle formed by this profile with said axis decreases monotonically from the leading edge to the trailing edge and in that the curve representing the value of the curvature along the profile of the blade as a function of the curvilinear abscissa to a slope whose value increases   from the leading edge to the trailing edge of the blade.   Apparatus according to claim 13, characterized in that   that said curve has a point of inflection.   Device according to one of the claims   previous, characterized in that it comprises a diffuser.   Device according to claim 15, characterized in that what it has blades.   17 Device according to claim 16, characterized in that said diffuser comprises between 8 and 30 blades and preferably 22 - between 15 and 25 blades.   Device according to one of the claims   preceding, characterized in that the axial length of the impeller relative to its outer diameter is between 0.10 and 0.40 and preferably between 0.15 and 0.20.   19 Apparatus according to one of the preceding claims,   characterized in that the means of the diffuser has a shape of revolution about the axis Ox, in that the line considered in an axial plane generating this form of revolution has at least one inflection point.   Device according to claim 19, characterized in that said line has tangents parallel to said axis at two ends of this line.   21 Use of at least one device described in   one of the preceding claims, in a multiphase pump.   22 Use in at least one device described in   one of the preceding claims in a multiphase pump   for pumping multiphase oil effluent.