FR2483019A1 - Compressor to separate gas and liquid - has plates projecting into rotor annulus to separate gas ring into variable volume zones - Google Patents

Abstract

The compressor rotor (2) has two end walls and two circumferential walls (7,8) dividing it into an inner space and an outer annular channel. A mixture of gas and liq. enters the inner space axially and after centrifugal compression enters the annulus through radial openings (21). Centrifugal action separates it into an outer liquid ring (15) and an inner gaseous one (16a,16b). Radial lips (18) on the inlet openings (21) separate the gas ring into two zones (16a,16b). They are further separated by liquid deflected by stationary plates (22) projecting axially from the stator. Liquid leaves through overflow openings (19) which also pass over stator ports to act as gas outlet valves.

Description

The present invention relates to a rotary compressor for gas and liquid mixtures.

In refrigeration plants, for example, hitherto compressors have been used sucking gas-liquid melanyes, separating the gas from the liquid and compressing the gas and finally discharging the gaseous and liquid components separately. These prior compressors are often complex, costly and large consumers of energy and have a relatively low flow rate compared to their size, cost price and energy consumption.

The object of the invention is to provide a simple and reliable rotary compressor for producing moderate pressure increases, for example of the order of 0.5 bar, and which has a relatively high flow rate or flow capacity. The compressor according to the invention is intended for the simultaneous pumping of a gas and a liquid and the passage of the liquid component serves to ensure gas tightness, cooling and lubrication. Thanks to a particular embodiment of the invention using the pumped liquid to perform said functions, it was possible to achieve a very simple construction and reliable operation.

The compressor according to the invention comprises a rotor mounted for rotation in a fixed pump body and having a circumferential gas and liquid channel, the compressor according to the invention being characterized in that the gas and liquid channel has an external annular space intended to enclose a liquid ring and an internal gas space which is concentric with said external space and which is delimited laterally by a side wall forming a liquid shutter and penetrating into the external annular liquid space, said internal gas space concentric with the liquid space being divided into suction and compression chambers, on the one hand, by means of one or more fixed transverse walls, supported by the rotor and penetrating into the space liquid ring and, on the other hand, by means of one or more planar liquid jets which are deflected from the rotating liquid ring, by means of one or more cutting blades which are anchored in the pump body and enter the space of the liquid ring.

The compressor according to the invention therefore comprises a rotor which cooperates with a liquid ring, as in the liquid ring pumps used hitherto, but it differs therefrom in many essential respects as regards construction and mode Operating.

In the compressor according to the invention, the rotor and the liquid ring are driven in concentric rotation, the liquid ring being enclosed in the rotor. The substantially complete absence of friction losses between the liquid ring and the rotor allows a high number of revolutions and a large flow or flow of the compressor.

The compression chamber is completely sealed with respect to the liquid ring by means of a liquid shutter arrangement, unlike the conventional liquid ring pumps in which it was necessary to inject a liquid at a pressure higher than the gas suction pressure, to seal the end walls of the compression chamber. On the other hand, in accordance with the present invention, the gas and the liquid can be aspirated at the same pressure. In addition, the evacuation of the compression chamber can be regulated by a distributor device with fixed flat surfaces on which slide outlet orifices which can be integrated into the rotor. Thus, it is possible to eliminate the non-return valves which can give rise to operating problems and create high resistance to evacuation at the high speeds at which the rotor must work. However, in the invention it is possible to dispense with non-return valves. In addition, the invention uses a new gas pumping mode, namely a compression of gas produced between a movable lamella carried by the rotor, and a stationary liquid barrier consisting of a jet or curtain of liquid through which said lamella or pallet can pass freely.

The invention will be described in more detail below with reference to the attached schematic drawings which show two embodiments and in which:
- Figure 1 shows an embodiment of the compressor according to the invention in axial section along line II in Figure 3;
- Figure 2 shows the compressor in cross section along line II-II in Figure 1 and shows in particular the liquid ring with two stationary liquid curtains;
- Figure 3 shows the compressor in cross section along line III-III in Figure 1 and shows in particular the plane sliding surfaces of the compressor;
- Figure 4 is a view similar to that of Figure 1 and shows a modified embodiment of the compressor according to the invention in section along line IV-IV in Figure 5;
- Figure 5 shows the embodiment modified in section along line VV in Figure 4; and
- Figure 6 shows in perspective a part of the rotor of Figure 5 in the area of an inlet and an outlet in a circumferential wall of the rotor.

The embodiment of Figures 1 to 3 comprises a fixed pump body l-in which a rotor 2 is rotatably mounted on a central drive shaft 3 which is sealingly mounted in a bearing box and cable gland 4. The rotor 2 is in the form of a wheel which has two opposite side walls 5, 6 spaced axially from each other, and circumferential, coaxial, double walls 7, 8. The side walls of the rotor, the inner circumferential wall 7 and the hub 9 of the rotor define an annular, closed central cavity 10, to which are connected a central suction opening 11 passing through the side wall 5, and an inlet duct 12 connected to the opening 11 and passing through a side wall 1 'of the let pump body being sealed with respect to the side wall 5 of the rotor by means of an annular seal 13 with low friction - to minimize friction losses during rotation of the rotor relative to the gasket.

In the embodiment of Figures 1 to 3, the outer circumferential wall 7 and two annular side walls 5 ', 6' form an annular cover or channel-shaped construction 14 which surrounds the rotor 2 circumferentially and is integral therewith, the wall circumferential wall 8 having an axial extension to the right in Figure 1 which is greater than that of the inner circumferential wall 7, so that the circumferential-outer wall 8 overhangs and projects axially from the right side wall 5, the wall lateral annular 5 'being in a plane located at an axial distance towards the outside of the plane of the lateral wall 5. The structure 14 described above, consisting of the walls 5', 6 'and 8, defines, with respect to the circumferential wall inner 7, an annular channel 14 coaxial with the rotor shaft. The channel 14 serves as a liquid shutter, so that an outer ring of liquid 15 rotated can be enclosed in the channel 14 and that an inner concentric gas channel 16 is sealed because an annular fin 17 integral with the rotor 2 and forming a radial extension of the side wall 5, enters the ring of rotary liquid 15. The gas channel 16 radially inside is therefore limited radially outwards by the liquid from the ring 15 radially outside and, radially inwards, by the inner circumferential wall 7 and finally laterally by the annular fin 17 and the annular side wall 6 '.

The annular gas channel 16 is divided into two separate halves (FIG. 2) by two strips or pallets in the form of transverse walls 18 integral with the rotor 2 and more precisely with the inner circumferential wall 7. The walls 18 protrude radially and penetrate into the liquid ring 15 to the same level as the annular fin 17.

In the gas channel 16, seen in the direction of rotation A of the rotor 2, there is provided in front of each transverse wall 18 a series of outlet channels or orifices 19 passing through the annular side wall 6 ', and behind each transverse wall 18 there is provided in the inner circumferential wall 7 an inlet channel 21 communicating the cavity 10 with the channel 14 containing the ring of = external liquid 15 and the internal gas channel 16. In the space 15 of the liquid ring two deflectors 22 are provided in the form of steel cutting blades, for example, which are fixed in two diametrically opposite positions and which have cutting edges 23 arranged obliquely against the direction of rotation of the rotor. The blades 22 are adapted to the inner face of the side wall 6 'of the channel 14, to the extreme edges of the transverse walls 18 and to the annular fin 17 and are carried by an annular disc 24 which enters the liquid ring 15 between the side wall eral annular right 5 'of the channel 14 and the neighboring rotor wall 5 carrying the annular fin 17, and which is connected to the wall 1' of the pump body 1 by means of a support 25.

The part of the lateral annular rotor side wall 6 ′, which is on the left in FIG. 1 and which forms a side wall of the channel 14, also forms a rotary distributor which is provided with the outlet orifices 19 described above and which is intended to turn in a sealed manner against two planar slide surfaces 26 in an arc of a circle, which are made up of flattened or rectified disc elements, for example of teflon, preferably supported by elastic supports 27, and which are shown in plan in FIG. 3 ′ and in end view in FIG. 1. The surfaces in an arc of a circle 26 which are separated from each other at their neighboring ends by spacings 28 (FIG. 3) serve to close the orifices outlet 19 and thereby block them against the return of gas during the compressor compression phases (see below). On the other hand, when the final pressure is obtained (maximum pressure for each compression phase), the passage will be free when the outlet orifices 19 are opposite the two diametrical spacings 28 between the neighboring ends of the regulating surfaces 26.

It should be noted that FIG. 1 shows in appearance the rotary orifices 19 and the fixed sliding surfaces 26 at different radial levels, which is explained by the fact that FIG. 1 is taken along line II in FIG. 3 In reality, the centers of the orifices 19 are, of course, located on the center lines of the surfaces 26.

A mixture of gas and liquid is introduced into the cavity of the rotor 2 through the stationary inlet duct 12. Compressed gas and liquid are evacuated from the pump body 1, for example by a lower outlet 29 for the liquid and a upper outlet 29 'for gas.

The compressor according to the invention operates as follows.

The gas-liquid mixture is introduced through the inlet duct 12 and the suction opening 11 into the cavity 10 of the rotor 2 which gives the gas-liquid mixture tangential and centrifugal acceleration in the cavity To increase the centrifugal effect , the rotor 2 may optionally be provided with internal radial wings 30 in the cavity 10. As a result of the rotation the liquid tends to separate from the gas and to accumulate on the inner face of the inner circumferential wall 7 of oit the liquid is discharged through the openings Z1 of the inner circumferential wall 7 and arrives at the annular channel 14 by entrainant gas. In the channel 14 the liquid is completely separated from the gas and accumulates, like a ring of liquid 15, on the internal face of the outer circumferential wall 8. Finally, the liquid is ejected through the orifices 19. In fact, it is advisable note that the orifices 19 serve as overflows for the liquid ring 15 and are intended to adjust the "level" of the ring 15, namely its radial thickness.

The cutting blades 22 which are in the fields of rotation of the liquid ring 15 form plowshares which deflect or become of the ring.

liquid from the high energy planar liquid jets 31 in the channel 14, the liquid jets or curtains being oriented obliquely inward against the inner wall 7 of the gas channel 14. Each jet 31 is returned to the liquid ring 15 as a result of the tangential flow and the deflection via the inner circumferential wall 7. Each jet 31 is stationary relative to the pump body 1 and is in the form of a liquid which flows in = curtain shape. The stationary curtains 31 and the transverse walls 18 rotating with the rotor divide the gas space 16 into two compression chambers 16a and into two suction chambers 16b separating the compression chambers. The volumes of these chambers alternately increase and decrease during the rotation of the rotor.

The transverse walls 18 produce a gas enclosure between the liquid ring 15, the outer circumferential wall 8 and the respective stationary jet 31, and compress the gas mass enclosed in the compression chambers 16a thus formed, the compressed gas mass being expelled through the outlet orifices 19 when they open, while the respective transverse wall 17 approaches the jet. It is easily understood that the transverse walls 18, during the rotation of the rotor 2, pass through the liquid curtains 31.

What is decisive for the gas compression conditions obtainable is the sealing power of the respective curtain 31 against the walls of the channel 14.

Generally speaking, it can be said that this sealing effect increases as the transverse orientation and the thickness of the liquid jets 31 become stronger. The degree of deflection and the thickness of the curtain are determined by the configuration of the cutting blades 22 and by the speed which is a function of the number of revolutions and the diameter of the rotor, and also by: the distance between the ring of liquid 15 and the inner wall 7 of the channel 14, since a pressure difference on the curtain or jet gives rise to a deviating tangential acceleration in the direction of rotation. To effectively use a jet 31 where the kinetic energy of the liquid is given, to ensure a good seal and a desired gas compression, the two halves of the inner circumferential wall 7 between its orifices 21 have an increasing radial pitch moving backwards the direction of rotation from the rear edge 21 'of the respective opening 21 over a certain distance, so that the gas-liquid channel 14 narrows over the corresponding distances, for example over two thirds of the length of each half of the walls 7. After this narrowing the curvature of the wall 7 takes place at a constant radius up to the respective transverse wall 18. Thus, the sealing property of the curtains 31 increases with increased compression of the gas which is trapped in the compression chambers 16a , 165 between the curtains and the transverse walls 18.

The outlet orifices 19 can advantageously be bored obliquely in the side wall 6 ′ of the channel 14, so that the pressure at the supports of the gas and of the liquid which exit is absorbed in the rotor 2.

The modifications of the embodiment of the invention according to FIGS. 1 to 3 fall within the scope of the invention. The stationary sliding surfaces 26, for example, can be supported by the annular disc 24 carrying the stationary cutting blades 22, the outlet orifices 19 being arranged in the side wall 5 ′ of the channel 14, which is on the right in FIG. 1 .

The blades 22, the transverse walls 18 and, consequently, the curtains 31 and the gas compression chambers 16a, 16b may, in principle, be one or more numerous.

The annular fin 17, instead of being integral with the rotor 2, can be rigidly connected to the pump body 1 or to the inlet channel 12 connected to the pump body, and can serve as a support for the cutting blade (s) 22 However, such an embodiment causes sealing problems between the cavity 10 and the gas channel 16 and also between the rotary transverse wall (or transverse walls) 18 and the annular fin 17.

The modified embodiment of Figures 4 to 6 is a preferred simplified mode of the compressor according to the invention. In FIGS. 4 to 6, the same reference numbers are used as far as possible as in FIGS. 1 to 3 to designate the identical details or the equivalent.

In this embodiment, the rotor shaft 3 is mounted inside the pump body 1 in a transverse and thrust bearing 40 and passes through the straight wall of the pump body, in which the shaft-3 is mounted so suitable and sealed by a bearing box and cable gland 4. As in the embodiment of FIGS. 1 to 3, the hub 9 of the rotor 2 is mounted on the shaft 3, the rotor being constituted by side walls 5, 6, a circumferential wall 7 and an outer structure 14 in the form of a channel which, in the embodiment of FIGS. 1 to 3, consists of an outer circumferential wall 8 and side walls 5 ′, 6 ′ and which around of the inner circumferential wall 7 defines a channel which in operation is divided into an outer channel with liquid ring 15 and an inner gas channel 16, an annular fin 17 integral with the rotor passing through the gas channel 16 and projecting into the liquid ring 15 whose level is determined é by one or more outlet orifices 19 which, in this case, are not dispensing orifices but only serve as overflow orifices determining the level of the liquid ring.

The annular cavity of the rotor 2 between the hub 9 and the shaft 3, on the one hand, and the inner circumferential wall 7, on the other hand, is divided into two chambers 10a, 10b, by a central partition 41, the conduit inlet 12 and opening 11 for the gas-liquid mixture leading to the rotor chamber 10a on the left in FIG. 4.

Similarly, the embodiment of FIGS. 4 to 5 presents two cutting blades 22 whose cutting edges 23 are oriented against the direction of rotation A of the rotor 2. The directions of flow of the curtains of liquid 31 stationary relative to the pump body 1 are indicated in FIG. 5 by arrows in solid line which also indicate the direction of entry of the gas-liquid mixture through the inlet 12 into the rotor chamber 10a and from the latter into the suction chambers 16b. Compressed gas from the compression chambers 16a, 1Gb, located between the transverse walls 18 and the liquid curtains 31, is not evacuated here by dispensing orifices as in the embodiment of Figures 1 to 3, but is conducted in the right rotor chamber 10b through openings in the circumferential wall 7 and passes from the chamber 10b through a central opening 42 of the side wall 6 of the rotor in a space 43 between the wall 6 and the wall adjacent to the pump body, where is eg The liquid passing through the overflow holes 19 is also led. The compressed gas and liquid are evacuated from the pump body by a common outlet 44. The flow of compressed gas from the compression chambers is indicated by arrows in broken lines.

The embodiment of FIGS. 4 to 6 working without distributors or valves therefore lacks slide surfaces 26 cooperating with the orifices 19 which serve only as liquid outlet orifices from the liquid ring 15 and which are intended determining the radial depth of the liquid ring.

The rotor chamber 10a which is on the left in FIG. 4 forms a low pressure chamber in which the mixture of gas and liquid coming from the inlet duct 12 is introduced at a relatively low pressure and is ejected therefrom, for example, by two outlet openings 21a from the inner circumferential wall 7, in the channel formed by the structure 14. It should be noted that each of the two openings 21a for discharging the gas-liquid mixture from the left chamber 10a in the channel of the structure 14 is only fitted in the half of the wall 7 which is located opposite the chamber 10a and, seen in the direction of rotation of the rotor, behind the corresponding transverse wall 18, while an outlet 21b for compressed gas of the respective compression chamber 16a is arranged in the half of the wall 7 which is opposite the rotor chamber 10b in front of the corresponding transverse wall 18 of the rotor, which is clearly shown in Figure 6. Compressed gas fromthe respective compression chamber 16a cannot therefore return to the inlet chamber 10a of the rotor.

There is no need for distributors or valves, but,
If desired, the openings 21b can be fitted with elastic return non-return valves which open at a certain pressure to allow the flow of gas from the compression chambers 16a to the rotor chamber 10b.

Because a relatively low pressure, namely the inlet pressure of the gas-liquid mixture, prevails in the space 45 between the rotor wall 5 and the wall 24 secured to the pump body 1, wall 24 which serves as a support blades 22 and which is tightly connected to the internal face of the pump body at 46, the level of the liquid in the ring 15 in the space 45 rises to a higher level, namely to a smaller radius rx, that the level ry to which the liquid rises in the space 46 between the fixed wall 24 and the annular wall 5 'forming a side wall of the structure forming channel 14 of the rotor. In space 46, the pressure is equal to that of the compressed gas in the pump body 1 between the rotor 2 and the internal face of the pump body. The level of liquid ry is lower than the level rx and the difference between these levels of liquid is equal to the pressure difference between the low pressure (the inlet pressure of the gas-liquid mixture) and the compression pressure of the gas.

As shown in Figure 5, the inner circumferential wall 7, as in the embodiment of Figures 1 to 3, has two transverse walls 18 and two cutting blades 22 and therefore two jets of liquid 31 and two chambers of compression 16a, 16b.

The orifices 19 acting only as overflows in this embodiment are dimensioned only to allow excess liquid from the ring 15 to escape.

In operation, the orifices 19 are in principle kept filled with liquid leaving the liquid ring 15. From the gas-liquid mixture which is accumulated on the internal face of the wall 7 and flows from the low pressure chamber 10a through the radial openings 21a in the channel 14, the liquid is separated from the gas as a result of the rotation and is placed in the liquid ring 15, while the gas fills the space between the liquid ring and the circumferential wall 7.

The compressed gas is expressed by the inlet openings 21b of the circumferential wall 7 of the rotor opposite the high pressure chamber 10b and enters it.

In this embodiment, the openings 21a and 21b are separated from each other by the transverse walls 18 and the rotor wall 41 and, as shown in FIG. 5, it is provided, preferably opposite the openings 21a and 21b, pairs of legs 7c, 7d curved obliquely inward in opposite directions, so that the legs 7c are oriented forward obliquely inward against the direction of rotation of the rotor to push, Like pallets, the gas-liquid mixture from the low-pressure chamber 10a to the channel structure 14, while the tabs 7d are oriented obliquely inwards backwards in the direction of rotation to conduct the gas from the compression chambers 16a to the high pressure chamber 10b in the rotor 2.

In the embodiment of Figures 4 to 6, the rotor lacks the wings 30 used in the embodiment of Figures 1 to 3 as means for increasing the centrifugal force. On the other hand, the pump body 1 is provided with fixed screens 47 inside the inlet opening 11 to restrict the rotation of the gas mixture in the low pressure chamber 10. The screens or wings 47 are integral with suitable way of the internal face of the pump body but, if desired, these means could be omitted.

The embodiment of FIGS. 4 to 6 can also be modified in various ways within the scope of the present invention.

Claims (11)

- - CLAIMS - 1. Rotary compressor for a mixture of gas and liquid, comprising a disc-shaped rotor (2) which is rotatably mounted in a fixed pump body (1) and has a circumferential gas and liquid channel (14) , characterized in that the channel (14) has a radially outer annular space (15) for holding. enclosed a liquid ring and a radially inner gas annular space (16) which is concentric with said liquid space (15) and which is defined by a side wall (17) forming a liquid shutter penetrating into the ring space liquid (15), and that the gas space (16) is divided into suction and compression chambers (16b respectively 16a), on the one hand, by one or more transverse walls (18) integral with the rotor (2) and penetrating radially from the interior into said liquid ring space (15) and, on the other hand, by planar liquid jets (31) which are deflected from the liquid ring rotating in space ( 15) by means of one or more cutting blades (22) which are anchored in the pump body (1) and which extend axially along the liquid ring space (15). 2. Compressor according to claim 1, characterized in that said side wall (17) is rigidly connected to the rotor (2). 3. Compressor according to claim 2, characterized in that the rotor (2) comprises at least one central cavity (10) with a central inlet opening (11), and what the central cavity (10) is connected to the gas annular space (16) by at least one suction inlet (21). 4. Compressor according to claims 1 to 3, characterized in that a cutting blade (22), at least 1 is fixed to a disc (24) which is anchored in the pump body (1) and-which enters the liquid ring space (15) wherein said blade, acting as a deflector, deflects a jet of liquid (31) from the liquid ring. 5. Compressor according to claims 1 to 4, characterized in that a plurality of outlet orifices (19) are arranged in a part of a side wall (6 ') defining said channel (14), and that the side wall part (6 ') has a flat sliding surface against a surface (26) serving as a slide and being integral with the internal face of the pump body (1). 6. Compressor according to claim 5, characterized in that said slide surface 26 is intended to close the orifices (19) during the compressor compression phases and to open them at the end of the compression phases in order to allow the compressed gas exhaust. 7. Rotor according to claim 1, characterized in that the gas space (16) is delimited radially inwards by a circumferential wall (7) of the rotor, wall which has an increasing radial pitch from the inlet opening (21) to a point where the desired compression condition is obtained, and which from this point to the transverse wall ( 18) has a constant radius. 8. Compressor according to claim 1, characterized in that the pump body (1) has a central inlet duct (11, 12) which is tightly connected to the cavity (10) of the rotor via of a rotary seal, and also comprises a lower outlet (29) for discharging compressed liquid and an upper outlet (29 ') for discharging compressed gas. 9. Compressor according to claim 1, characterized in that the rotor (2) has a circumferential wall (7) surrounded by a structure (14) forming a channel and defining said gas and liquid channel around said circumferential wall (7) of the rotor, that the circumferential wall (7) has at least one opening (21î 21a, 21b) and surrounds a cavity (10) in the rotor, which is connected to an inlet (11, 12) for the gas-liquid mixture, which the pump body (1) carries at least one deflector means (22) which is disposed in said liquid ring space (15) and which is intended to deflect from the ring of liquid rotating with the rotor a jet of stationary liquid (31) against said circumferential wall (7) of the rotor, which itself is intended to return said jet in the liquid ring in a tangential direction, and that said circumferential wall carries at least one transverse wall (18) projecting radially so as to penetrate into the liquid ring and being intended, with said jet (31) and side walls of the channel structure (14), to divide the space gas (16) in a compression chamber (16a) and in a suction chamber (16b) whose volumes increase and decrease alternately between zero and a maximum value during the rotation of the rotor, the transverse wall (18) being intended to pass radially inside said deflector means (22) and, after gas compression phases, to pass through the liquid jet (31), that the rotor has means (19) to keep the level of the liquid from said ring and that the compressor has means (19, 26, 29, 29 ', 21b, 42, 43, 44) for discharging compressed gas from said compression chamber t16a). 10. Compressor according to claim 9, characterized in that the cavity (10) of the rotor is divided by a transverse, central wall (41) of the rotor into two chambers (lOa, lOb) axially separated from one another and forming a first chamber (10a) and a second chamber (10b) the first of which is connected to said inlet (11, 12) for the gas-liquid mixture, while the second chamber (10b) is connected to an outlet (44 ) for discharging compressed gas, that the first gas opening is arranged in said circumferential wall (7) in the half thereof which is opposite the first chamber (10a) to allow the gas-liquid mixture to be conducted said first chamber (lova) to the gas and liquid channel surrounding the circumferential wall (7) of the rotor, while the second opening (21 b) is opposite said second chamber (lOb) in the corresponding half of the circumferential wall (7) that said two openings (21a, 21b) are arranged on either side of the transverse wall (18) projecting radially and integral with the circumferential wall (7), so that the two said openings (21a and 21b) are separated from each other at the face outer of the circumferential wall (7) by said transverse wall projecting radially, and are separated axially from each other to the inner face of the circumferential wall (7) lar said transverse wall (41) separating said first chamber said second chamber (lOa respectively lOb), so that the gas-liquid mixture is sucked into a suction chamber (16b) of the first chamber (lova) of the rotor, at the same time as compressed gas is discharged from a compression chamber (16a) at said second chamber (10b) of the rotor during the rotation thereof. 11. Compressor according to claim 9, characterized in that said structure (14) defining said gas and liquid channel around the circumferential wall (7) of the rotor has a device forming a rotary distributor and having orifices (19) leading from said gas and liquid channel and opening onto a stationary flat surface (26) supported by the pump body and intended to open and close the distributor orifices (19) alternately during rotation of the rotor, so that these orifices open to allow 11 evacuation of compressed gas at the end of each compression phase and they are then closed by said flat surface (26).