WO2018130752A1

WO2018130752A1 - Dual axial pump

Info

Publication number: WO2018130752A1
Application number: PCT/FR2017/000257
Authority: WO
Inventors: Christian Bratu
Original assignee: Christian Bratu
Priority date: 2017-01-16
Filing date: 2017-12-21
Publication date: 2018-07-19
Also published as: FR3061936B1; FR3061936A1

Abstract

The invention relates to a dual axial pump including at least one pumping stage (1) provided with a pumping device (2) rotating inside a stationary casing (12). The pumping device (2) comprises rotary closed channels (8) formed by the integral assembly; the rotor (3), the axial blades (5, 6, 7) and the outer cylinder (4). Thus, the dual axial pump is intended for transporting fluid mixtures made up of more or less viscous liquids, gas and a proportion of solid particles. For this purpose, the rotary pumping device (2) provides a flow confined in the sealed closed channels (8), thus protecting against contact between the rotary portion (2) and the stationary casing (12). Also, the axial blades (5, 6, 7) have a specific configuration, suited to the pumping of fluid mixtures. The architecture of the dual axial pump considerably increases the reliability and the hydraulic efficiency of the transport of complex fluid mixtures.

Description

DUAL AXIAL PUMP.

The present invention relates to a dual axial pump architecture, allowing for a significant increase in reliability and hydraulic performance.

Industrial pumping often carries mixtures of several phases: liquids of variable viscosity, gases and solid particles. Under these conditions, hydraulic performance (pressures, flow rates) and reliability (erosion, corrosion) and operating time depend on the composition of the pumped fluid mixture.

For example, for the pumping of complex products, the petroleum industry uses centrifugal pumps (PC) with the helical-axial variant (HA), and progressive cavity-type volumetric pumps (PCP). Helico-axial pumps (HA) are used for multiphasic production (liquids and gases) by the petroleum industry (IFP, Sulzer, Schlumberger).

In order to describe the architecture of the dual axial pump, according to the present invention, we begin by showing the operation of traditional pumps highlighting the processes that condition the reliability and hydraulic performance: pumping more or less viscous liquids, pumping liquid mixtures with gas and solid particles

Centrifugal pumps (PC).

In general, for the pumping of liquids (medium viscosity), with no other phase (gas or solid particles), PCs perform better than volumetric pumps (PCP). Indeed, the PCs have an all-metal configuration allowing them to achieve high speeds of rotation (for example 3000 revolutions / minute). Under these conditions the PCs produce large flows with good operational reliability. In multiphase pumping (liquids and gases), given the centrifugal force field, the PCs separate the phases of the pumped fluid mixture; under these conditions, the gas is concentrated in the middle and the liquid is directed to the outer wall. Gas pockets block flow and PC performance declines significantly; a gas rate of about 30% is the limit of use of PCs.

For this reason, helico-axial pumps (HA), capable of monotonic axial flow keeping the gas mixed with the pumped liquids, are used. Thus, the HAs reduce the phase separation effect; HA can pump liquid mixtures with a gas rate of about 60%.

Despite this improvement, the monotonic flow on the long helical-axial blades (HA) greatly limits the rise in pressure. HAs achieve low pressures.

In general, the pumping of fluid mixtures containing solid particles (sand, for example) leads to the degradation of the reliability of the PCP, PC and HA pumps.

In the case of PCs, the centrifugal field accelerates the separation of the phases and the solid particles concentrate on the outer wall causing a sharp degradation of the rotating rotor blades relative to the fixed casing.

The essentially axial flow of the HA pumps does not exclude the centrifugation of the solid particles (by contrast of the densities between the particles and the pumped fluids), which causes the erosion process, in contact with the blades with the crankcase, thus reducing the reliability and operational duration.

The pumping of highly viscous fluids by PC systems is limited and the ability of the centrifugal accelerations field to drive viscous fluids is reduced.

In fact, the pumping of highly viscous fluids is favorable for PCP or HA axial flow pumps. Progressive Cavity Pumps (PCP).

PCPs have an elastomer stator in tight contact with the metal rotor, which limits the rotational speed (for example, 300 all / min). Thus, the liquid flow rates of the pump and the reliability of the elastomer stator are limited.

However, PCP pumps have a volumetric axial flow capable of achieving high pressures, even in multiphase pumping (liquid and gas).

The pumping of fluid mixtures containing solid particles (sand, for example) leads to the degradation of the reliability of PCP pumps, especially in the presence of chemical and thermodynamic processes.

Indeed, given the configuration of the PCP, the solid particles are concentrated in contact with the rotating metal rotor with the fixed stator elastomer; the erosion process leads to the deterioration of the stator reliability and the significant reduction in operating time.

In summary, for the pumping of fluid mixtures (more or less viscous liquids, gases and solid particles) the operation of the centrifugal pumps (PC and HA) and volumetric with progressive cavities (PCP) strongly penalizes the performances: reliability and reduced operating duration, as well as the degradation of the hydraulic performances.

The present invention aims at a new dual axial pump architecture to significantly increase the reliability and operational life as well as the hydraulic performance of the pump.

In general, the dual axial pump proposed is characterized by new devices, whose dual nature is unpublished: the dual axial pump comprises at least one pumping stage, comprising a pumping device consisting of a rotor with axial blades and an outer integral cylinder, the assembly thus forming closed rotating channels; the closed metal pumping device (without elastomer) ensures smooth transport with high mechanical reliability

the pumping device comprises a first large-diameter portion, designed to increase the pressure of the pumped fluids, followed by a device of reduced diameter capable of rearranging the kinematics of the flow and of transferring the flow towards the outlet of the pumping floor

the axial blades of the pumping device have a double curvature, longitudinal and radial, in order to organize the kinematics of the flow in the channels, to ensure the quasi-homogeneous maintenance of the pumped fluid mixture (more or less viscous liquids, gas solid particles).

Thus, this new dual axial pump is dedicated to the transport of fluid mixtures, accompanied by chemical and thermo-dynamic processes :: more or less viscous liquids, gases and solid particles.

Various industrial sectors are concerned by the use of this dual axial pump: the oil and gas industry, chemicals, food, wastewater treatment.

For these purposes, the present invention provides a dual axial pump having at least one pumping stage 1, having an inlet and an outlet, said pumping stage 1 being provided with a pumping device 2 rotating inside the pumping stage 1. a fixed housing 12, said pump device 2 comprising:

a rotor 3 comprising a system of axial blades 5, 6 whose diameter, geometry and number of blades vary between the inlet and the outlet, and

an outer cylinder 4 of variable diameter decreasing between the inlet and the outlet; said outer cylinder 4 being integral with said rotor 3 via said axial blade system 5, 6

n said pumping device 2, thus forming closed channels 8 between said outer cylinder 4, said axial blades 5,6 and said rotor 3; said pumping device 2 being rotatable to transmit energy to the pumped fluid mixture flow rate;

a said pumping device 2 having a large-diameter portion 2a adapted to increase the pressure of the pumped fluid, followed by a device of reduced diameter 2b adapted to reorganize the kinematics of the flow and to transmit the flow to the outlet

n said pump device 2 being disposed inside a fixed casing 12 by means of a sealing system 9 placed between said rotating outer cylinder 4 and said fixed casing 12;

said pump device 2 being configured to significantly improve the mechanical reliability of the assembly and to ensure the flow of the fluid mixture by increasing the pressure, increasing the flow rate and transferring to the outlet of said pump stage 1.

According to a non-limiting embodiment of the dual axial pump, said outer cylinder 4 may comprise on the inner face of other partial axial blades 7, complementary to said axial blades 5,6 of said rotor 3.

Thus, said pumping stage 1 of the dual axial pump is characterized in that inside said pumping device 2, said axial blades 5,6 of said rotor 3 and said outer cylinder 4 form closed channels 8 sealed relative to said housing 12, said closed channels 8 being configured to allow:

to significantly reduce the separation of the phases contained in the pumped fluids (different liquids, solid particles, gas pockets)

- the increase of the pressure and the increase of the flow of the pumped fluids, taking into account the axial flow, reputed to have a small radial component

- the balancing of the flow-pressure torque and the transfer of the mixture of pumped fluids to the outlet

- Improving the mechanical reliability, by maintaining the solid particles and / or viscous fluids in the flow confined within said rotating channels 8, without access between said outer cylinder 4 in rotation and said fixed housing 12.

According to a non-limiting embodiment of the dual axial pump, said axial blades 5 of said rotor 3 have a double curvature, longitudinal and radial 11, adapted to ensure:

the regular flow in said closed channels

the limitation of the dissipation of the radial energy, in contact with said axial blades 5, with said outer cylinder 4

- The maintenance of liquids, gas pockets and solid particles in the flow, thus limiting phase separation.

According to an embodiment of the dual axial pump, said longitudinal curvature of said axial blades is described by a linear function of the entry (a) and exit (β) angles of said blades.

5. Also, the radial curvature 11 of said axial blades 5 is described by a slope of about 10% to 20%. The dual axial pump comprises at least one of said pumping stage 1. Under these conditions, to ensure the transfer of fluids between two successive pumping stages 1, said pumping stage 1 is followed by fixed rectifiers adapted to guide the flow to the pump. input of said next pump stage 1.

The invention relates to the application of the dual axial pump as mentioned above to the pumping of fluid mixtures, said fluids being more or less viscous liquids, gas pockets and a proportion of solid particles in the flow.

The invention will be better understood on reading the description which follows, given solely by way of non-limiting example, with reference to the drawings:

- Figure 1 is an axial section of the pumping stage 1, according to one embodiment of the present invention. Section A represents the view through the inlet while section B shows the view of the outlet of the pumping stage 1. This figure 1 also shows the pumping device 2 and the part dedicated to increasing the pressure 2a and the portion of the transfer of the flow 2b to the outlet of the pumping stage 1. The sealing device 9 protects the contact of the rotating part (the pumping device 2) and the fixed housing 12. .

- Figure 2 is a view of the pumping device 2 showing the integral mounting of the outer cylinder 4 of the rotor 3 via the axial blades 5.6.

FIG. 3 is an axial section of the first part of the pumping device 2a showing the closed channels

8 and the profile of axial blades 5 with double curvature, longitudinal 10 and radial 11. Section C shows the closed channels 8 and the radial curvature 11 of the axial blades 5. The profile D of the axial blade 5 (along the outer path abc), shows the angles (, β) and the longitudinal curvature of the axial blade 5. FIG. 4 is a view of the arrangement of the complementary axial blades 7, attached inside the outer cylinder 4. The section F shows the coupling of the axial blades 5 with the complementary blades 7 in the closed channels 8. The section E is a view of the inlet of the pumping stage 1, on which are represented the axial blades 5 and the complementary blades 7.

The dual axial pump, according to one embodiment of the present invention, comprises at least one pumping stage 1.

As shown in FIG. 1, the pumping stage 1 comprises a pumping device 2 able to rotate in a fixed casing 12, the fluid mixture being pumped between the inlet and the outlet of the pumping stage 1.

Thus, the pumping device 2 comprises a rotor 3 provided with a set of axial blades 5,6 and an outer cylinder 4, integral with the rotor 3 via the axial blade system 5,6.

Consequently, inside the pumping device 2, the integral arrangement of the rotor 3 with the axial blades 5, 6 and the outer cylinder 4 forms closed closed channels 8 which are sealed with respect to the fixed casing 12.

Section A is the view through the inlet while section B is the view through the outlet of the pumping stage 1.

FIG. 2 represents the mode of arrangement of the pumping device 2. Once the rotor 3 has been made with the axial blades 5, 6, the outer cylinder 4 is installed making it integral with the rotor 3 by means of the axial blades 5. . The entire pumping device 2 is rotating: the closed channels 8 constituted by the integral arrangement of the rotor 3, the axial blades 5 and the outer cylinder 4.

According to FIG. 3, between the rotor 3 and the outer cylinder 4, the axial blades 5 form closed channels 8 rotating, in which the pumped mixture is confined; the abrasive components of the pumped fluid mixture are contained in the confined flow without access to the contacts between the rotating and stationary parts.

In order to completely limit the access of the abrasive components of the pumped fluid mixture (solid particles), through the outlet of the pumping stage 1, a sealing system 9 is installed between the rotating pumping device 2 and the stationary casing 12 ( Figure 1 ) .

Consequently, the pumped fluid mixture is confined in the closed channels 8 of the rotating pumping device 2, which avoids abrasive contact of the mixture pumped between the rotating parts of the pumping device 2 and the fixed casing 12. In these conditions, the confinement of the flow of the pumped fluid mixture in the closed channels 8 of the pumping device 2 ensures a good mechanical reliability, by protecting the contact between the rotating pumping device 2 and the stationary casing 12.

All parts of the pumping stage 1 are metallic, without any elastomer component; thus the reliability is significantly improved.

As a result, the dual axial pump benefits from a significant improvement in mechanical reliability, which ensures an efficient operational life.

The pumping device 2 comprises a first large-diameter portion 2a, designed to provide the pressure of the pumped fluid mixture, followed by a reduced diameter device 2b designed to rearrange the kinematics of the flow and transfer the flow to the output of the pump. the pumping stage 1 (Figure 1).

The geometry of the first part 2a, characterized by the flow diameter and the number and shape of the axial blades 5, determines the flow rate and the pumping pressure.

The theoretical formulation (I) confirmed by the results experimental, determines the geometrical parameters of the pumping device 2 according to the hydraulic performance required: the pressure (P) or the pumping height (H) and the flow (Q).

Thus, we obtain the diameter D and the geometry of the axial blades 5, characterized by the angles of the profile (, β), taking into account the flow rate Q and the pumping height H (or the pressure P):

V = Q / SP = pgH U = QR = aD / 2 tga = V / U tg β = VU / (U ² -g, H) (I)

H. g = K. U ² . [1 - V. ctg β / U]

U ... speed of rotation of the axial blade

a ... angle of entry of the axial blades with respect to U

β ... angle of exit of the axial blade with respect to U

V ... relative speed of the pumped fluid

H ... the pumping height

P ... the pumping pressure

D ... diameter; R the radius

Ω ... speed of rotation (cycles / s)

Q ... flow density of fluids

p ... density of fluids

S ... surface of the flow section

K ... coefficient of loss of load,

in particular the viscosity of the mixture pumped as well as the local and frictional hydraulic losses

Therefore, the first part of the pumping device 2a, dedicated to the pumping pressure (P or H), comprises a large diameter D and axial blades 5 whose angles (α, β) are adapted to the required performances: the height pumping H (or the pressure P) and the flow rate Q. Indeed, the rotational speeds U of the axial blades 5 transmit to the fluid the kinetic energy, which generates the pressure and the flow.

Thus, the diameter D and the profile of the axial blades 5 play an important role in the generation of pressure and the transport of high flows through closed channels 8.

However, it is observed that the flow velocities in the closed channels 8, proportional to the rotational speed U (formula I), vary in the radial direction of the pumping device 2.

Consequently, the second part of the pumping device 2b has a reduced-diameter convergent shape, adapted to reorganize the kinematics of the flow (uniform speeds) and to transmit the flow towards the outlet of the pumping stage 1.

This convergent shape ensures a potential flow whose kinematics is regular; and the axial blades 6 of the second part 2b have regular profiles whose angle is equal to that of the output (β) of the axial blades 5. The purpose of the dual axial pump of the present invention is to pump fluid mixtures composed of more or less viscous liquids, gases and a proportion of solid particles. Under these conditions it is important to keep the fluid mixture uniform and to avoid phase separation in the closed channels 8.

Also, the closed channels 8 significantly improve the homogeneity of the flow, because the outer wall of the channels 8 is in rotation integral with the assembly; the turbulent boundary layer improves hydraulic performance.

The geometry of the blades 5 and their number assume the transport of the fluid mixture: the realization of the pressure and the pumping rate, as well as the maintenance of the homogeneous flow inside the closed channels 8.

As FIG. 3 shows, the axial blades of the pumping device 5 have a double curvature; longitudinal 10 and radial 11. The angles of entry and exit of the axial profile (α, β) define the longitudinal curvature 10 capable of ensuring the pressure of the axial blades 5. According to one embodiment, the longitudinal curvature of the blades 10 axial 5 is a linear function of the angles of entry (a) and exit (β).

As for the radial curvature 11, it compensates for the radial component of the flow in order to limit the phase separation and the dissipation of the energy. From the practical point of view, a radial slope 11 of the profile of the axial blade 5 of about 10% to 20% ensures the consistency of the fluid mixture. Formula (I) shows the role of the exit angle (β) of the axial blades 5 in obtaining the pumping height (H).

In general, the relative velocities V of the flow depend on the pressure drops; the coefficient K is a function of the viscosity of the fluid mixture and the local and frictional hydraulic losses.

To avoid cavitation, the angle of entry (a) must be limited; thus, experience shows that an angle of about 20 ° - 30 ° provides good inlet flow.

As for the exit angle (β), it depends on the pumping height H; the experiment often leads to values of about 40 °.

For the pumping of highly viscous fluids, the rotational speed (U, Ω) is adapted in order to maintain good operating conditions of the axial blades (formulas I). For example, a high viscosity significantly reduces the flow velocities V, which implies the reduction of the rotational speed U; thus one can keep the same axial blades to pump viscous fluids.

In general, for the pumping of viscous mixtures or with gas, the use of a set of distributed axial blades is necessary to ensure a good transmission of energy to the pumped mixtures. To do this, the concept of the dual axial pump provides the possibility of introducing complementary blades 7 attached to the inside of the integral outer cylinder 4. According to one embodiment, FIG. 4 shows an example of arrangement using the blades. complementary axial 7. For gas mixtures, the maintenance of quasi-homogeneous flow is very important; under these conditions a good turbulence rate limits phase separation, which requires a specific distribution of axial blades. The closed channels 8 facilitate the arrangement of the axial blades 5 on the rotor 3 with an arrangement of the complementary blades 7 on the outer cylinder 4 (Figure 4).

Thus, the dual axial pump has several possibilities of using axial blades 5 and 7 on the rotor 3 and on the outer cylinder 4, thus producing closed channels 8 adapted to pumping complex fluid mixtures: more or less viscous liquids , a high rate of gas and solid particles.

Under pumping conditions for liquids (eg water or oil), the dual axial pump achieves hydraulic performance (pumping height and flow) equivalent to centrifugal (semi-axial) pumps:

D = 100 mm, N = 3500 rpm

a = 20 °; β = 40 °; H = 8m; Q = 200 m3 / day

According to the present invention, the dual axial pump comprises at least one pumping stage 1. In the case of the multi-stage pump architecture 1, fixed rectifiers are installed to guide the flow at the inlet of the next pump stage 1.

The present invention relates to the architecture of the dual axial pump whose reliability and hydraulic performance are significant advances compared to other existing pumping systems: - the reliability and the operational life are significantly improved by the confinement of solid particles and viscous fluids in the closed channels, which avoids the abrasive contact between the rotating and fixed parts

the transport of the fluid mixture is axial, which reduces the separation of the phases (liquids, gases, solid particles)

- The pumping of complex fluid mixtures (more or less viscous liquids, gases and solid particles) is done with good hydraulic performance: pressure and flow

Claims

1. - Dual axial pump comprising at least one pumping stage 1, having an inlet and an outlet, said pumping stage 1 being provided with a pumping device 2 rotating inside a fixed housing 12,

said pump device 2 comprising:

a rotor 3 comprising a system of axial blades 5, 6 whose diameter, geometry and number of blades vary between the inlet and the outlet,

an outer cylinder 4 of variable diameter decreasing between the inlet and the outlet; said outer cylinder 4 being integral with said rotor 3 via said axial blade system 5,6

n said pumping device 2, thus forming closed channels 8 between said outer cylinder 4, said axial blades 5,6 and said rotor 3; said pumping device 2 being adapted to rotate said closed channels 8 in order to transmit the energy to the pumped fluid mixture flow rate;

n said pumping device 2 having a large-diameter portion 2a adapted to increase the pressure of the pumped fluid, followed by a device of reduced diameter 2b adapted to reorganize the kinematics of the flow and to transmit the flow to the output

n said pumping device 2 being disposed inside a fixed casing 12 by means of a sealing system 9 placed between said rotating outer cylinder 4 and said fixed casing 12;

2. - dual axial pump according to claim 1, characterized in that said outer cylinder 4 may comprise on the inner face of other partial axial blades 7, complementary to said axial blades 5,6 of said rotor 3.

3. - dual axial pump according to claims 1 and 2, characterized in that said pumping stage 1 is characterized in that inside said pumping device 2, said axial blades 5,6 of said rotor 3 and said outer cylinder 4 form closed channels 8 sealed relative to said housing 12.

4. - dual axial pump according to any one of claims 1 to 3, characterized in that said axial blades 5 of said rotor 3 have a double curvature, longitudinal and radial 10, adapted to ensure:

the regular flow in said closed channels

maintaining liquids, gas pockets and solid particles in the flow, thereby limiting phase separation.

5. - dual axial pump according to any one of claims 1 to 4, characterized in that said axial blades 5 of said rotor 3 have the longitudinal curvature 10 described by a linear function of the angles of entry (a) and exit ( β) of said axial blades 5.

6. - dual axial pump according to any one of claims 1 to 5, characterized in that said axial blades 5 of said rotor 3 have a radial curvature 11 described by a slope of about 10% to 20%.

7. - Dual axial pump according to any one of

Claims 1 to 6, characterized in that said pumping stage 1 is followed by fixed rectifiers adapted to guide the flow at the inlet of said next pumping stage 1.

8. - Application of the dual axial pump such that

claimed in any one of claims 1 to 7, pumping the fluid mixtures, said fluids being more or less viscous liquids, gas pockets and a proportion of solid particles in the flow.