EP1559913A1 - Progressive cavity pump - Google Patents

Abstract

The pump has cavities (4) formed between a helical rotor (2) and a helical stator (3). A hydraulic regulation system (7) is installed in the rotor for ensuring internal recirculation of fluid pumped between the cavities under conditions to ensure distribution of pressures along the pump, stabilization of the temperatures, control of leakage rate, and compensation of the volumes of compressed gas. An independent claim is also included for an application of progressing cavities pump for pumping of compressible multiphase mixture and pumping of viscous fluid.

Description

The present invention relates to improvements brought to volumetric pumps of the type to progressive cavities, also say Sparrow pump, and more specifically it relates to a volumetric pump of type with progressive cavities, perfected, allowing pump single-phase mixtures or effluents or polyphasic, having any viscosity, in particular mixtures or multiphase effluents compressible and viscous to very viscous fluids.

(a) une phase gazeuse formée d'au moins un gaz libre ; et

(b) une phase liquide formée d'au moins un liquide et/ou

(c) une phase solide formée par des particules d'au moins un solide en suspension dans (a) et, si la phase (b) est présente, dans (a) et/ou (b).

"Compressible multiphase mixture or effluent" means an effluent composed of a mixture of:

(a) a gaseous phase formed of at least one free gas; and

(b) a liquid phase formed of at least one liquid and / or

(c) a solid phase formed by particles of at least one solid suspended in (a) and, if phase (b) is present, in (a) and / or (b).

However, as indicated above, the pump according to the present invention allows a fortiori to pump a single phase or a liquid phase charged with particles solids, with varying viscosities.

The progressive cavity pump - designated also hereinafter by the abbreviation PCP - was invented by René Moineau in 1930 and the operation in liquid industrial pumps currently used corresponds basic principles.

Figure 1 of the attached drawing gives, in (A), a schematic representation partially in longitudinal section axis of a conventional PCP pump, also with (B) a representation of the distribution of pressures on along the pump in the case of pumping a liquid (curve L) and in the case of pumping a mixture polyphasic liquid-gas (curve P).

The architecture of the PCP 1 pump is made up a helical metal rotor 2 rotating inside a compressible stator 3, generally of elastomer, of helical inner shape. The contact between the rotor 2 and the stator 3 is by compression, more or less strong, of the stator 3. To do this, the rotor 2 has a diameter D (FIG. 2 (B)) greater than the stator channel 3 (Figure 2 (C)), which generates a compression contact of the stator 3 by the rotor 2 (contact clamping), ensuring a certain seal (Figure 2 (A)).

As can be seen in FIGS. 1 (A) and 2 (A), the geometry of the rotor 2 and the stator 3 of the PCP pump 1 leads to a set of isolated cavities 4, defined between the rotor 2 and the stator 3, also called cells , of constant volume, that the rotor 2 moves from the suction or inlet 5 (low suction pressure p _A ) to the discharge or outlet 6 (high discharge pressure p _R ). In this sense, the PCP pump is a positive displacement pump.

In the following, the term is sometimes used "Floor" instead of "cavity"; we hear by "Stage" the volume between the stator and the rotor corresponding to a cavity at a given moment. These two terms are sometimes used interchangeably.

• le pas (P_S) du stator 3 est le double du pas (P_r) du rotor 2 ; et
• la longueur L d'une cavité 4 est égale au pas (P_s) du stator 3, et par conséquent, elle est le double du pas (P_r) du rotor 2.

Figure 2 of the accompanying drawing shows a known PCP pump 1 shown in (A) in the assembled state and having a single helical rotor 2 shown alone in (B) and a double helical stator 3 shown alone in (C). The axis of the stator is designated by _s and the axis of the rotor by _r . In these conditions :

• the pitch (P _S ) of the stator 3 is twice the pitch (P _r ) of the rotor 2; and
• the length L of a cavity 4 is equal to the pitch (P _s ) of the stator 3, and therefore it is twice the pitch (P _r ) of the rotor 2.

The distribution of pressures (Figure 1 (B)) to along the pump 1 of the discharge 6 towards the suction 5, and lubrication of the rotor contact 2 / stator 3 are due leakage flow between the rotor 2 and the stator 3. A cavity 4 at high pressure flows towards the cavity 4 adjacent to a lower pressure due to leaks because the contact rotor 2 / stator 3 is not entirely tight, and pressure losses generate pressure differential between the cavities 4. Therefore, the leakage rate depends on contact tightness between the rotor 2 and the stator 3, dynamic conditions of their contact (rotation speed, vibrations), viscosity fluid and the difference in local pressures. In practical, it is difficult to control the flow of leakage and distribution of the pressures it generates.

In other words, hydraulic operation of the PCP pump is subject to external regulation at cavities, due to leakage between the rotor 2 and the stator 3, this regulation is not controlled.

In the case where the PCP pump 1 is used for pumping a multiphase mixture comprising a gaseous phase, the cavity 4 moves from the low pressure of the suction 5 towards the high delivery pressure 6 and the presence of the gas in the pumped effluent leads to a process of compression of the gas with development of temperature, because the cavity is of constant volume. The thermodynamic law of gas shows that if the volume in which the gas is compressed remains constant, the temperature rises considerably. Thus, the leakage rate through the annular contact rotor 2 / stator 3 fulfills two functions: it partially compensates the volume of compressed gas and it realizes the differential pressure between the cavities 4. However, the annular leakage rate between the rotor 2 and the stator 3 of the pump PCP 1 is adapted to the operation in liquid (incompressible fluid), for the purpose of lubrication with low flow rates; it is not sufficient to compensate for gas compression. Since the leakage rate is low, the last cavities 4 are only partially compensated and the compression occurs on the last stages of the pump, as can be seen in FIG. 1 (B), where p _A designates, as already indicated. , the suction pressure and p _R designating the discharge pressure. This compression is accompanied by a high temperature. The concentration of the pressures at the outlet of the pump and the strong increase in temperature leads to the risk of mechanical damage: stator degradation, mechanical expansion and vibrations.

Therefore, the concept of contact leakage rotor / stator, unique to the PCP pump, is unsuitable for pumping a compressible multiphase mixture.

Practically, in the presence of gas, the PCP pump achieves a pressure of 4 MPa (40 bar) on the four top floors, with a strong pressure gradient that develops high temperatures; on thirteen floors he there are only four that compress the mixture.

In general, the irregular distribution of pressures along the PCP pump leads to the development excessive temperatures involving reliability of the pump: degradation of the stator elastomer, dynamic instability of the rotor, deformations and efforts thermal structure. In these conditions, it is necessary limit the discharge pressure and reduce the speed of rotation of the pump, which leads to a degradation pumped flows.

Experience also shows that contact impervious rotor / stator can lead to development cavitation when the PCP pump carries liquid viscous, especially for large pumping rates or when the pressure at the entrance is low. The appearance of cavitation is very damaging to the resistance of the stator elastomer and rotor, so to the reliability of system.

• Il a ainsi été proposé de réaliser un couple rotor/stator dont le volume des cavités diminue de l'aspiration vers le refoulement. C'est ainsi que le document US 2 765 114 propose un système rotor/stator tronconique, avec les diamètres décroissants.Dans le même sens, on peut imaginer un rotor à pas variable dont le volume des cavités est décroissant vers le refoulement.Ces solutions ne sont efficaces que pour un taux de gaz fixe et elles pénalisent le fonctionnement en liquide. Par ailleurs, cette solution ne peut pas éviter l'apparition de la cavitation.Aussi, la modification de l'architecture de la pompe conduit à un processus de fabrication complexe sans en assurer une bonne fiabilité.
• Il a aussi été proposé de réaliser un contact entre rotor et stator qui est variable au long de la pompe.

Several technical solutions to standardize the pressures along a PCP pump have been proposed:

• It has thus been proposed to provide a rotor / stator torque whose cavity volume decreases from suction to discharge. Thus, the document US Pat. No. 2,765,114 proposes a frustoconical rotor / stator system with decreasing diameters. In the same direction, it is possible to imagine a rotor with variable pitch whose volume of the cavities is decreasing towards the discharge. are effective only for a fixed gas rate and they penalize the operation in liquid. Moreover, this solution can not avoid the appearance of cavitation. Also, the modification of the architecture of the pump leads to a complex manufacturing process without ensuring a good reliability.
• It has also been proposed to make a contact between rotor and stator which is variable along the pump.

Indeed, if one makes a contact between rotor and stator such as annular leakage flow (between the rotor and the stator) is stronger towards the repression and weaker on the suction side, the compensation of the volume of compressed gas is done under more conditions favorable and the distribution of pressures improves.

Thus, US 5,722,820 proposes a variable rotor / stator contact decreasing backflow to suction.

To realize this system, several means are proposed: a slightly frustoconical variation of the rotor, or a frustoconical stator, or a combination of both.

In these conditions, the leakage flow between the rotor and the stator carry the flow necessary for the compensation in pressure and volume of cavities lying downstream of the pump. It is a global leakage rate; he first compensate the last cavity, to move to the next and so on.

To feed several cavities, whose rate of compression is large, it requires a large leakage flow, this which requires very little contact between the rotor and the stator. However, the mechanical and hydraulic pump PCP requires contact between rotor and stator to ensure dynamic stability and hydraulic efficiency.

This solution can only be a compromise between liquid operation, like PCP, and the transport of gas; It is for this reason that practical use is limited to low flow rates gas.

Moreover, the tightening of the contact between the rotor and the stator is only valid for a fixed gas rate and penalizes the cash yield.

In viscous fluid, the pump can not avoid the appearance of cavitation.

Also, this solution modifies the architecture of the pump and complicates the manufacturing process.

Therefore, this solution can not have limited use and uses a complex architecture without ensuring good reliability.

The present invention aims to propose an improved pump so as to spread the aforementioned drawbacks of the previous state of the technical.

For these purposes, a pump with progressive cavities having a helical rotor rotating inside a helical stator, said stator and said rotor being arranged so that the cavities formed between said rotor and said stator move from the suction towards the repression, is characterized, being arranged according to the invention, by the fact that means of hydraulic regulation are provided to ensure a internal recirculation of the fluid pumped between at least two said cavities under conditions capable of providing the least one function among the pressure distribution searched along the pump, the stabilization of temperatures, control of leak rates, and the compensation of compressed gas volumes.

Internal recirculation means the recirculation between two cavities of a mixing volume pumped as opposed to an external recirculation cavities that is done by the annular contact between the rotor and the stator and that generates a leakage flow.

The pressure distribution is obtained by a rebalancing of local pressures due to the flow of recirculation of hydraulic regulators.

The leakage rates between the stator and the rotor are a function of the pressure gradient. The control of pressures leads to control of leak rates.

Compensation of compressed volumes is ensured by the recirculation flow of the regulators Hydraulic.

The role of the hydraulic control means is therefore to control the behavior of the pump, according to production characteristics.

Pressure control and compensation volume of compressed gas stabilizes temperatures, multiphase pumping (liquid, gas, solid particles).

By controlling the pressures, we avoid the appearance of cavitation, a source of damage mechanical (stator elastomer, rotor metal); and balancing the pressures and controlling the flow of leakage lead to the mastery of the contact between the stator and rotor.

Indeed, the internal regulation of the pressure by the hydraulic control system of the present invention leads to the stabilization of the thermal regime and hydraulic along the pump, and can improve thus the mechanical behavior and the reliability overall.

In these conditions, behavioral control hydro-thermo-mechanical ensures better performance hydraulic (pumped flow, discharge pressure) and economic (maintenance, service life).

The mastery of the contact between rotor and stator means that one can have a superficial contact without a strong compression between stator and rotor, while keeping low leakage rate. This is a way of new operation compared to the PCP pump Traditional.

• la fiabilité du système est améliorée ;
• on peut utiliser des matériaux plus rigides (plus résistants) pour le stator afin d'augmenter la vitesse de rotation et le débit de la pompe.

In these conditions :

• the reliability of the system is improved;
• stiffer (more resistant) materials can be used for the stator to increase the rotational speed and pump flow.

• la pompe PCP avec un contact rotor/stator tronconique utilisée actuellement est un système global de régulation externe, dont le débit de fuite limité ne compense que les cavités situées près du refoulement de la pompe ;
• la pompe selon la présente invention comporte des moyens de régulation hydraulique interne assurant un écoulement local de recirculation, entre deux cavités, pour compenser la pression différentielle locale, le débit de fuite et la compression du gaz contenu dans la cavité ;
• le débit de recirculation est auto-régulé par le taux de gaz et la pression différentielle.

Thus the operating principle of the pump according to the present invention is new and very different compared to existing systems:

• the PCP pump with a frustoconical rotor / stator contact currently used is a global external control system, whose limited leakage rate only compensates for the cavities located near the discharge of the pump;
• the pump according to the present invention comprises internal hydraulic control means ensuring a recirculation local flow, between two cavities, to compensate the local differential pressure, the leakage rate and the compression of the gas contained in the cavity;
• the recirculation flow rate is self-regulated by the gas ratio and the differential pressure.

The hydraulic control means are advantageously arranged to ensure recirculation internal fluid pumped between at least two cavities adjacent. In particular, these means can advantageously be arranged to ensure internal recirculation pumped fluid between at least two cavities located in the region of the pump close to the discharge. These means can also be arranged to ensure internal recirculation of the fluid pumped between all cavities of the pump.

The hydraulic control means can be received at least in part by the rotor and / or at least partly by the stator.

For this purpose, it is advantageous to inside the pump a set of regulators hydraulics, the dimensioning and density of which of the pump ensure a uniform regulation hydraulic system consisting of the control of pressures, leakage rates and temperatures, and the compensation of compressed volumes. Rotation of the rotor displaces cavities along the pump with a speed dependent on speed of rotation and pitch of the rotor; every time a cavity passes in front of a hydraulic regulator, the recirculation flow rate compensates the compressed volume, rebalances pressures and stabilizes temperatures.

Therefore, the density of the regulators hydraulics ensures the continuity of the process of regulation along the pump; this density is performance of the pump (flow, distribution pressures).

At the same time, the dimensioning of regulators hydraulic is the recirculation flow needed for the cavity for volume compensation compressed and rebalancing pressures.

In these circumstances, the functioning of hydraulic regulators is self-regulating; the flow of recirculation depends on the pressure and vice versa.

According to a first embodiment in particular, the hydraulic control means, ensuring internal recirculation of the pumped fluid between two cavities, have at least one channel practiced in the rotor connecting these two cavities, the regulation hydraulically being carried out mechanically using a regulator arranged inside said channel and / or by loss of charge.

According to a second embodiment in particular, the hydraulic control means, ensuring internal recirculation of the pumped fluid between two cavities, have at least one peripheral channel hosted by the rotor and arranged to provide the link between these two cavities with regulation by loss of charge.

According to a third embodiment in particular, the hydraulic control means, ensuring internal recirculation of the pumped fluid between two cavities, have at least one hydraulic channel interior welcomed by the stator and arranged to ensure the connection between these two cavities with regulation by loss of charge.

The three particular embodiments can be used simultaneously on the same pump.

According to an interesting feature of the present invention, the contact between the rotor and the stator can be loosened compared to a pump at progressive cavities not including the means of hydraulic control as defined above. In these conditions, we can increase the rotation speed and the pumped flow without damaging the stator.

The present invention also relates to the application of the pump as defined above to the pumping compressible multiphase mixtures and pumping viscous fluids.

Industrial applications of the pump according to the present invention cover a wider area than that of existing PCP pumps.

Outside the transport applications of aforementioned multiphase mixtures which are in the field of chemistry and oil, we can mention the pumping at large flows (oil field for example ...) and pumping with low pressure at the entrance (oil wells horizontal).

• la figure 1 représente une pompe PCP traditionnelle, comme cela a été décrit ci-dessus, avec une représentation des distributions des pressions en pompage du liquide et du mélange polyphasique liquide-gaz ;
• la figure 2 représente la composition d'une pompe PCP avec un rotor à simple hélice et un stator à double hélice ;
• la figure 3 est une vue analogue à la figure 1, donnant en (A) une représentation d'une pompe à cavités progressives selon la présente invention, avec représentation schématique des régulateurs hydrauliques (RH), et donnant en (B) une représentation de la distribution des pressions en pompage polyphasique uniforme le long de la pompe ;
• la figure 4 est, à plus grande échelle, une vue analogue à la figure 3, donnant en (A) une représentation d'une section de la pompe de l'invention, permettant de décrire le mécanisme de recirculation locale pour la compensation des volumes comprimés et le rééquilibrage des pressions locales, dans trois cavités successives de la pompe respectivement 1, m et n, et donnant en (B) une représentation de la distribution des pressions le long de la pompe ;
• la figure 5A est, encore à plus grande échelle, une vue analogue à la figure 4, d'une section de pompe de l'invention, montrant le régulateur hydraulique (RH) comportant un canal pratiqué dans le rotor pour assurer la recirculation du fluide pompé entre deux cavités adjacentes 1, m, avec régulation mécanique ;
• la figure 5B est une coupe selon la ligne A-A de la figure 5A ;
• la figure 6 montre, encore à plus grande échelle, le régulateur mécanique de la figure 5 ;
• la figure 7A est une vue analogue à la figure 5, mais avec régulation hydraulique par perte de charge ;
• la figure 7B est une coupe selon la ligne A-A de la figure 7A ;
• la figure 8A est une vue d'une section de pompe de l'invention, montrant le régulateur hydraulique (RH) comportant deux canaux parallèles pratiqués dans le rotor pour assurer la recirculation du fluide pompé entre deux cavités adjacentes, 1, m, avec régulation mécanique ;
• les figures 8B et 8C sont des vues en coupe respectivement selon les lignes A-A et B-B de la figure 8A ;
• la figure 9A est une vue analogue à la figure 8, mais avec régulation par perte de charge ;
• les figures 9B et 9C sont des vues en coupe respectivement selon les lignes A-A et B-B de la figure 9A ;
• la figure 10A est la vue d'une section de pompe de l'invention, montrant le régulateur hydraulique (RH) comportant un canal hydraulique périphérique au rotor pour assurer la recirculation du fluide pompé entre deux cavités adjacentes, 1, m ;
• la figure 10B est une vue en coupe selon la ligne A-A de la figure 10A ;
• la figure 11A est une vue d'une section de pompe de l'invention, montrant le régulateur hydraulique (RH) comportant deux canaux périphériques au rotor, décalés de 180° et d'un 1/2 de pas du rotor, pour assurer la recirculation du fluide pompé entre deux cavités adjacentes, 1, m ;
• les figures 11B et 11C sont des vues en coupe respectivement selon les lignes A-A et B-B de la figure 11A ;
• la figure 12A est la vue d'une section de pompe de l'invention montrant le régulateur hydraulique (RH) comportant un canal hydraulique périphérique à l'intérieur du stator, permettant d'assurer la recirculation du fluide pompé entre les deux cavités adjacentes, 1, m ; et
• la figure 12B est une vue en coupe selon la ligne A-A de la figure 12A.

To better illustrate the subject of the present invention, a number of particular embodiments given solely by way of nonlimiting examples will be described below, with reference to the appended drawings in which:

• FIG. 1 represents a conventional PCP pump, as described above, with a representation of the pumping pressure distributions of the liquid and the multiphase liquid-gas mixture;
• Figure 2 shows the composition of a PCP pump with a single helix rotor and a double helix stator;
• FIG. 3 is a view similar to FIG. 1, giving in (A) a representation of a progressive cavity pump according to the present invention, with schematic representation of the hydraulic regulators (RH), and giving in (B) a representation of the distribution of pressures in uniform multiphase pumping along the pump;
• FIG. 4 is, on a larger scale, a view similar to FIG. 3, giving in (A) a representation of a section of the pump of the invention, making it possible to describe the local recirculation mechanism for the compensation of volumes. compressed and rebalancing local pressures, in three successive cavities of the pump respectively 1, m and n, and giving in (B) a representation of the distribution of pressures along the pump;
• FIG. 5A is, even on a larger scale, a view similar to FIG. 4, of a pump section of the invention, showing the hydraulic regulator (RH) comprising a channel made in the rotor for recirculating the fluid. pumped between two adjacent cavities 1, m, with mechanical regulation;
• Figure 5B is a section along line AA of Figure 5A;
• Figure 6 shows, even on a larger scale, the mechanical regulator of Figure 5;
• Figure 7A is a view similar to Figure 5, but with hydraulic control by pressure drop;
• Figure 7B is a section along line AA of Figure 7A;
• FIG. 8A is a view of a pump section of the invention, showing the hydraulic regulator (RH) comprising two parallel channels made in the rotor to ensure the recirculation of the fluid pumped between two adjacent cavities, 1, m, with regulation mechanical ;
• Figures 8B and 8C are sectional views respectively along lines AA and BB of Figure 8A;
• Figure 9A is a view similar to Figure 8, but with loss of pressure regulation;
• Figures 9B and 9C are sectional views respectively along lines AA and BB of Figure 9A;
• Fig. 10A is a view of a pump section of the invention, showing the hydraulic controller (RH) having a hydraulic channel peripheral to the rotor for recirculating pumped fluid between two adjacent cavities, 1, m;
• Figure 10B is a sectional view along line AA of Figure 10A;
• FIG. 11A is a view of a pump section of the invention, showing the hydraulic regulator (RH) having two peripheral channels to the rotor, offset by 180 ° and a 1/2 of the pitch of the rotor, to ensure recirculating the fluid pumped between two adjacent cavities, 1, m;
• Figures 11B and 11C are sectional views respectively along lines AA and BB of Figure 11A;
• FIG. 12A is the view of a pump section of the invention showing the hydraulic regulator (RH) comprising a peripheral hydraulic channel inside the stator, making it possible to recirculate the fluid pumped between the two adjacent cavities, 1, m; and
• Figure 12B is a sectional view along line AA of Figure 12A.

Figures 3 and 4 illustrate the operation of the hydraulic control device (RH) of the invention installed inside the pump.

Q = Q_L + Q_G :

le débit total du mélange de liquide (L) et de gaz (G) ;

Q :

débit de recirculation entre les cavités ; par exemple, q_m est le débit du dispositif de régulation hydraulique de la cavité m vers la cavité 1 ;

P :

pression locale, dans les cavités (1, m, n) ;

ζ :

coefficient de perte de charge du dispositif de régulation hydraulique ;

S :

section d'écoulement du dispositif de régulation hydraulique ;

γ :

coefficient de transformation adiabatique.

We notice :

Q = Q _L + Q _G :

the total flow rate of the mixture of liquid (L) and gas (G);

Q:

recirculation rate between the cavities; for example, q _m is the flow rate of the hydraulic control device from cavity m to cavity 1;

P:

local pressure, in cavities (1, m, n);

ζ:

load loss coefficient of the hydraulic control device;

S:

flow section of the hydraulic control device;

γ:

adiabatic transformation coefficient.

The total flow rate Q accesses the cavity 1 and the volume of gas is compressed at the pressure p ₁ . Because of the pressure difference (p _m - p ₁ ), the flow rate q _m of the hydraulic control system compensates the compressed volume in the cavity 1 and rebalances the pressures p _m and p ₁ .

• le débit de recirculation q_m revient dans le circuit de régulation hydraulique vers la cavité 1 ;
• le débit Q avance dans la cavité m, poussé par le rotor ;
• à cause de la pression p_m, supérieure à la pression précédente p₁, le volume de gaz est comprimé ;
• la différence de pression (p_n - p_m) génère un débit q_n dans le système de régulation hydraulique, de la cavité n vers la cavité m, pour compenser le volume comprimé dans la cavité m et rééquilibrer les pressions p_n et p_m ;
• le débit total (Q + q_n) avance dans la cavité n ; le débit de recirculation q_n revient dans la régulation hydraulique (RH) vers la cavité m ;
• le débit Q de la pompe est comprimé, le système de régulation hydraulique débite pour compenser la compression et rééquilibrer les pressions.

The total flow rate (Q + q _m ), compressed at the pressure p ₁ , passes into the cavity m;

• the recirculation flow q _m returns in the hydraulic control circuit to the cavity 1;
• the flow rate Q advances in the cavity m, pushed by the rotor;
• because of the pressure p _m , greater than the previous pressure p ₁ , the volume of gas is compressed;
• the pressure difference (p _n - p _m ) generates a flow q _n in the hydraulic control system, from the cavity n to the cavity m, to compensate for the compressed volume in the cavity m and to rebalance the pressures p _n and p _m ;
• the total flow (Q + q _n ) advances in the cavity n; the recirculation flow q _n returns in the hydraulic control (RH) to the cavity m;
• the flow rate Q of the pump is compressed, the hydraulic control system delivers to compensate the compression and rebalance the pressures.

The process is repeated for each cavity, towards the discharge.

• rééquilibre localement les pressions entre deux cavités, ce qui conduit à la régularisation de la distribution des pressions au long de la pompe ;
• compense les volumes comprimés, ce qui évite la remontée de la température ;
• le débit pompé Q se conserve ; la recirculation selon l'invention se fait sans perte de débit ;
• par le rééquilibrage des pressions on maítrise les débits de fuite et le contact entre rotor et stator.

Therefore, local recirculation by the hydraulic control system (RH) ensures internal regulation, between the cavities:

• locally rebalances the pressures between two cavities, which leads to the regularization of the distribution of pressures along the pump;
• compensates compressed volumes, which prevents the rise of temperature;
• the pumped flow rate Q is conserved; recirculation according to the invention is without loss of flow;
• by rebalancing the pressures, the leak rates and the contact between the rotor and the stator are controlled.

Local operation of the control system hydraulic system of the invention is the opposite of the systems currently used by the industry: this is a controlled internal regulation, in contrast with the external regulation without control of current systems.

The mastery of the performances is done by the architecture of the hydraulic control system: dimensions, transfer function, layouts the pump.

Given the local operation, the dimensioning of the hydraulic control system done following the methods of fluid mechanics compressible and thermodynamic.

Thus, the dimensions and the recirculation flow rate are a function of the gas and liquid flow rate, the differential pressure, and the hydraulic characteristics of the RH (pressure drop, transfer function): q not = f {Q BOY WUT Q The , (p m / p not ) 1 / γ , p not , p m , S, ζ}

From a thermodynamic point of view, the local pressures and the recirculation flow (q) are connected by the relation [2]: [p not / p m ] 1 / γ = 1 + q not / Q BOY WUT

Therefore, the evolution of local pressure [2] depends on recirculation flow and vice versa [1], the recirculation flow depends on the pressures local.

At equilibrium, the distribution of pressure resulting from pressure drops in the system of hydraulic regulation, which determines the dimensions of the hydraulic control system [1].

From a practical point of view, we give ourselves the gradient of pressure along the pump to reach in conditions polyphasic, then the recirculation flow rate is determined [2] and the dimensions of the control system hydraulic system [1] corresponding to the distribution of pressures requested.

• éviter l'apparition de la cavitation, avec les dommages qu'elle engendre sur le stator et le rotor ;
• contrôler le contact entre rotor et stator : débit de fuite, lubrification du contact rotor/stator ;
• obtenir une meilleure fiabilité et augmentation du rendement hydraulique : débit, pression de refoulement, durée de vie, maintenance.

In liquid pumping, the hydraulic control system regulates from inside the pressure distribution and the leakage flow, which corresponds to the control of the hydraulic operation of the pump, aiming at:

• avoid the appearance of cavitation, with the damage it causes on the stator and the rotor;
• check the contact between rotor and stator: leakage flow, lubrication of the rotor / stator contact;
• to obtain better reliability and increased hydraulic efficiency: flow, discharge pressure, service life, maintenance.

This is the opposite of the current PCP pump: the hydraulic operation by the external regulation of pressures and leaks is not controlled.

Under these conditions, the control systems are installed inside the pump by adapting the rotor and / or the stator, without changing completely the initial architecture of the whole of the PCP pump and its manufacture. Maintaining the configuration the original PCP pump means that no modifications not the overall architecture (the rotor and the stator), the transport of the mixture by the displacement of the cavities, the motorization.

The results obtained on a pump of the invention in two-phase production conditions (gas and liquid) demonstrate the effectiveness of the system; the control of the distribution of pressures along the pump (distribution standardized) and the (stabilized) thermal regime. In fluid control of hydraulic operation without cavitation is confirmed.

Figures 5 to 12 show achievements particular of the pump according to the invention.

In FIGS. 5A and 5B, the control system hydraulic RH 7 is constituted by a hydraulic channel 8 which is practiced inside the rotor 2 between two cavities 4 and in which is installed a device for regulation 9 of the recirculation flow.

A practical embodiment of the device 9 is shown schematically in Figure 6, where one can see that this device is based on a valve gradually opening to a differential pressure given, which leads to the regulation of the flow of recirculation q (Figure 4 (A)).

In FIGS. 7A and 7B, the regulation system RH 7 consists of a hydraulic channel 8 practiced inside the rotor 2 between two cavities 4.

The pressure losses at the entrance, along and at the channel 8 output regulate flow and pressure differential.

In Figures 8A-8C and 9A-9C, the system of RH 7 hydraulic control consists of two channels 10, one being practiced between the cavities 1 and m, and the other inside the cavity 1. These two tandem channels, arranged in an offset fashion, represent the simplest structure. The fact that we realize several channels decreases their diameter and the offset ensures better circulation, especially when the opening of the channel in contact with the stator.

Figures 8A-8C show a variant in which a flow control device 9, such as the one shown in Figure 6, is installed in each channels 10 of the tandem, and FIGS. 9A-9C a variant according to which, in each channel 10 of the tandem, the hydraulic regulation is carried out by the pressure drop, as shown in Figs. 7A, 7B.

In FIGS. 10A, 10B and 11A-11C, the system of hydraulic control RH 7 is realized by a channel peripheral hydraulic rotor 2, between two cavities 4. Thus, it ensures the recirculation between the two cavities 4 and the differential pressure is given by the loss of charge of the flow. Its dimensions correspond to recirculation flow required.

Figures 10A, 10B show a variant having a single-channel hydraulic circuit 11, and FIGS. 11A-11C a variant comprising two circuits 12 in tandem shifted.

In FIGS. 12A, 12B, the regulation system hydraulic RH 7 has a hydraulic channel 13 internal device to the stator 3, practiced between two cavities 4.

As in the previous case, he ensures the recirculation between two cavities, the pressure differential is given by the pressure drop, and its dimensions correspond to the recirculation flow.

The following examples illustrate results obtained with the pump according to the invention without however limit the scope of the latter.

Example 1

This test concerns a PCP pump prototype traditional carrying a multiphase mixture (water and air).

PCP pump with thirteen stages (cavities) transports a polyphasic mixture whose flow rates are 50% water and 50% air, with a suction pressure of 0.1 MPa (1 bar) and a pressure in the conduit of pressure of 4 MPa (40 bar), which is equivalent to gas compression of 40/1. Due to the high rate of compression and the fact that the leakage flow (between rotor and stator) is unable to compensate for the volume of compressed gas, the discharge pressure is carried out on the last four floors (cavities), which amounts to a high pressure gain of 1 MPa (10 bar) / stage. All the work of the pump is carried out by the last four floors, the remaining nine floors of the pump does not not contributing to the compression of the mixture. This strong localized compression on the last floors is accompanied by a strong rise in temperature: inlet temperature is doubled.

The high temperature and the concentration of pressure at the outlet of the pump are damaging to the mechanical strength of the assembly, in particular the elastomer of the stator and the rotor.

Example 2

This test concerns a PCP pump prototype perfected with the Hydraulic Regulators (RH), carrying a multiphase mixture (water and air).

The pump according to the present invention has a quite different behavior; thanks to regulators Hydraulic RH installed in the rotor, the distribution pressures are standardized and the temperature stabilized. On the last four floors, the density of hydraulic regulators RH is two regulators hydraulics per floor and therefore the gain of pressure is very low (about 0.1 MPa / stage). On the nine remaining floors of the pump, the regulators hydraulics RH are distributed as a regulator RH per floor. In these circumstances, the distribution of pressure is standardized, which amounts to a gain of pressure of about 0.3 MPa (3 bar) / stage.

Therefore, the standardization of the distribution pressures along the pump leads to a low pressure gain of each floor and at the temperature stabilization along the pump.

The density variation of the regulators hydraulics RH contributes to hydro-thermo-mechanical rebalancing the pump; all floors contribute to the compression of the mixture.

Example 3

This test concerns a PCP pump prototype traditional carrying a liquid (water).

The same PCP pump carries water with a low pressure at the inlet (0.1 MPa (1 bar)) and a pressure of about 0.5 MPa in the discharge pipe. Because of the dynamic behavior of the contact between rotor and the stator, the pump develops very high pressures weak on floors 7-11 with risk of cavitation.

Therefore, the appearance of cavitation leads to damage of materials, especially elastomer of the stator and the rotor metal.

Example 4

This test concerns a PCP pump prototype perfected with Hydraulic Regulators (RH) carrying a liquid (water).

Thanks to RH hydraulic controllers, the pump according to the present invention controls the distribution of pressures and therefore the pressures are positive and uniformly distributed, without risk of cavitation. Of pressure at 0.5 MPa (5 bar), pressures vary evenly up to the suction pressure 0.1 Mpa (1 bar), without ever reaching locally low cavitation pressures.

Claims (11)

Progressive cavity pump comprising a helical rotor (2) rotating inside a helical stator (3), said stator (3) and said rotor (2) being arranged so that the cavities (4) formed between said rotor (2) and said stator (3) move from the suction (5) to the discharge (6), characterized in that hydraulic control means (RH) are provided to ensure internal recirculation of the fluid pumped between at least two of said cavities (4) under conditions capable of providing at least one of the desired pressure distribution along the pump, stabilization of temperatures, control of leak rates, and compensation of gas volumes compressed. Pump according to claim 1, characterized in that the hydraulic control means (RH) are arranged to ensure internal recirculation of the fluid pumped between at least two cavities (4) adjacent. Pump according to claim 1 or 2, characterized in that the hydraulic control means (RH) are arranged to ensure internal recirculation of the fluid pumped between at least two cavities (4) located in the region of the pump (1) neighbor of repression (6). Pump according to claim 1 or 2, characterized in that the hydraulic control means (RH) are arranged to ensure internal recirculation of the fluid pumped between all the cavities (4) of the pump (1). Pump according to any one of claims 1 to 4, characterized in that the hydraulic control means (RH) are at least partly accommodated by the rotor (2). Pump according to claim 5, characterized in that the hydraulic control means (RH), ensuring the internal recirculation of the fluid pumped between two cavities (4), comprise at least one channel (8) formed in the rotor (2) connecting these two cavities (4), the hydraulic control being performed mechanically using a regulator (9) disposed within said channel (8) and / or by pressure drop. Pump according to claim 5, characterized in that the hydraulic control means (RH), ensuring the internal recirculation of the fluid pumped between two cavities (4), comprise at least one peripheral channel (11) accommodated by the rotor (2) and arranged to ensure the connection between these two cavities (4) with loss of pressure regulation. Pump according to any one of claims 1 to 7, characterized in that the hydraulic control means (RH) are at least partly accommodated by the stator (3). Pump according to claim 8, characterized in that the hydraulic control means (RH), ensuring the internal recirculation of the fluid pumped between two cavities (4), comprise at least one internal hydraulic channel (13) accommodated by the stator (3). ) and arranged to ensure the connection between these two cavities (4) with loss of pressure regulation. Pump according to any one of claims 1 to 9, characterized in that the contact between the rotor (2) and the stator (3) is loosened with respect to a progressive cavity pump not comprising the hydraulic control means such as as defined in one of claims 1 to 8. Application of the pump as defined in any one of claims 1 to 10, pumping compressible multiphase mixtures and pumping of viscous fluids.

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