Fluid treatment machine with improved sealing

Abstract

Method for controlling a fluid treatment machine comprising a casing (10) defining a chamber at a first pressure and a chamber at a second pressure, the chambers being separated from each other by a rotary seal (70) comprising two labyrinth sections axially separated by an intermediate space in which a third pressure prevails. The method comprises the step of regulating the third pressure by taking as setpoint a difference between the second pressure and the third pressure. Machine for implementing this method.

Description

Fluid handling machine with improved sealing.

[0001] The present invention relates to the field of fluid treatment machines such as thermal machines subjecting a working fluid to cyclic transformations, such as turbomachines, industrial turbocompressors, motor-compressors, motor-turbocompressors, used for example in a thermodynamic refrigeration cycle of the reverse Brayton type (commonly called turbo-brayton)… By treatment, we mean any operation carried out on fluids such as simple circulation, compression, expansion…

[0002] BACKGROUND OF THE INVENTION

[0003] Such a fluid processing machine generally includes a housing defining a first chamber in which is pivotally mounted a shaft which has one end projecting into a second chamber and which carries an element, such as an impeller, rotating in the second chamber.

[0004] The first chamber contains one or more components used for the operation of the machine, such as a motor for driving the shaft in rotation and bearings for guiding the shaft in rotation. A first fluid circuit is connected to the first chamber to circulate a fluid at a first pressure in order to cool the components located in the first chamber.

[0005] A second fluid circuit is connected to the second chamber to circulate the fluid to be treated at a second pressure. The second fluid circuit comprises, for example, a heat exchanger.

[0006] In known installations, the first pressure is lower than the second pressure and it is desired to prevent the fluid to be treated from entering the first chamber. To this end, the first chamber is separated from the second chamber by a rotating joint through which the shaft passes.

[0007] Several types of rotary joints exist. In industrial installations, the rotary joint, which is most often of the type commonly called a labyrinth joint, comprises a plurality of first annular projecting elements, integral with the casing and separated two by two by a first groove; and a plurality of second annular projecting elements, integral with the shaft and separated two by two by a second groove. The first projecting elements have an internal diameter smaller than the external diameter of the second projecting elements so that the first projecting elements and the second projecting elements are nested within each other. The projecting elements (commonly called lips) thus form labyrinth passages which limit the leakage flow and therefore the transfer of fluid between the two chambers.

[0008] Since it is impossible to prevent a leak with this type of rotating joint, it is known to provide an intermediate space between two labyrinth sections of the rotating joint and to connect this intermediate space to a fluid injection circuit making it possible to inject, into said space, a fluid having characteristics compatible with the first chamber to maintain in the intermediate space a pressure close to the second pressure prevailing in the second chamber. The passage of the fluid to be treated towards the first chamber is thus blocked while the fluid injected into the intermediate space leaks towards the first chamber through the labyrinth section adjacent to it, which is not a problem. The fluid injection circuit comprises a mechanical pressure reducer having a setpoint inlet connected to a conduit connected to the second chamber. However, with such a device, it is the pressure at the pressure reducer which is regulated as a function of the second pressure.However, the pressure at the regulator is not equal to the pressure in the intermediate space, particularly due to the pressure losses induced in the line connecting the regulator to the intermediate space.

[0009] SUBJECT OF THE INVENTION

[0010] The invention aims in particular to provide a fluid treatment machine free from all or part of the aforementioned drawbacks.

[0011] To this end, the invention provides a method for controlling a fluid treatment machine, comprising a casing defining a first chamber in which a shaft is mounted to pivot having an interface facing a second chamber, the first chamber being connected to a first fluid circuit to maintain a first fluid pressure in the first chamber, the second chamber being connected to a second fluid circuit so that the interface is subjected to a fluid to be treated at a second pressure, the first chamber being separated from the second chamber by a rotating joint comprising two labyrinth sections axially separated by an intermediate space in which a third pressure prevails. The method comprises the step of regulating the third pressure by taking as a setpoint a difference between the second pressure and the third pressure.

[0012] Thus, the regulation no longer has as its setpoint the pressure in the second chamber but the pressure difference between the second chamber and the intermediate space. This allows for very precise regulation.

[0013] For the implementation of this method, a first treatment machine is provided comprising a casing defining a first chamber in which a shaft is mounted to pivot having an interface opposite a second chamber, the first chamber being connected to a first fluid circuit to maintain a first fluid pressure in the first chamber, the second chamber being connected to a second fluid circuit so that the interface is subjected to a fluid to be treated at a second pressure, the first chamber being separated from the second chamber by a rotating joint comprising two labyrinth sections axially separated by an intermediate space in which a third pressure prevails.The machine comprises at least one pressure determining device determining the pressure in the intermediate space and in the second chamber which is connected to a pressure regulating device, the regulating device being connected to a tapping opening into the intermediate space and having as a setpoint a difference between the second pressure and the third pressure to maintain in said intermediate space the third pressure substantially equal to the second pressure.

[0014] According to additional characteristics of this machine, considered individually or combined together in whole or in part: the regulating device comprises an electronic control circuit controlling at least a first solenoid valve and the determining device is connected to the electronic control circuit to provide it with an electrical signal representative of the pressure to which they are subjected. the first solenoid valve is connected to a pressure source lower than the second pressure and the regulating device comprises a second solenoid valve connected to a pressure source higher than the second pressure. the first solenoid valve is a three-way solenoid valve connected to a pressure source lower than the second pressure and to a pressure source higher than the second pressure. the regulating device comprises a manual valve. the interface is a rotating element.the rotating element is a turbine wheel or a compressor wheel. the first chamber receives a motor for driving the shaft, the motor being coaxial with the shaft. the determination device comprises two pressure probes mounted to be subjected to the pressure prevailing respectively in the second chamber and in the third chamber and to provide the regulation device with an electrical signal representative of the pressure to which they are subjected.

[0015] A second treatment machine is also provided comprising a casing defining a first chamber in which a shaft having an interface opposite a second chamber is mounted for pivoting, the first chamber being connected to a first fluid circuit to maintain a first fluid pressure in the first chamber, the second chamber being connected to a second fluid circuit so that the interface is subjected to a fluid to be treated at a second pressure, the first chamber being separated from the second chamber by a rotating joint comprising two labyrinth sections axially separated by an intermediate space, The machine comprises: a first tap opening into the intermediate space and a second tap opening into the second chamber;a pressure regulating device having a setpoint port connected to the first tapping and to the second tapping and an inlet / outlet port connected to a third tapping opening into the intermediate space to maintain in said intermediate space a third pressure substantially equal to the second pressure.;

[0016] According to additional characteristics of this machine, considered individually or combined together in whole or in part: the regulating device is a pressure reducer. the interface is a rotating element. the rotating element is a turbine wheel or a compressor wheel. the first chamber receives a shaft drive motor, the motor being coaxial with the shaft.

[0017] In both machines, the regulating device no longer has as its setpoint the pressure in the second chamber but the pressure difference between the second chamber and the intermediate space. This makes it possible to automatically take into account any pressure losses in the line connecting the pressure regulating device to the intermediate space.

[0018] Other characteristics and advantages of the invention will emerge from reading the following description of a particular and non-limiting embodiment of the invention.

[0019] Reference will be made to the attached drawings, including:

[0020] is a partial schematic view of a fluid treatment machine according to the invention;

[0021] is a partial schematic view, in axial section, of this machine according to the invention, without the fluid circuits;

[0022] is a partial view, in axial section, of one of the rotating joints of this machine;

[0023] is a schematic view of a pressure regulating device according to a first embodiment of the invention;

[0024] is a schematic view of a pressure regulating device according to a second embodiment of the invention;

[0025] is a schematic view of a pressure regulating device according to a third embodiment of the invention;

[0026] is a schematic view of a pressure regulating device according to a fourth embodiment of the invention;

[0027] is a partial schematic view of a fluid treatment machine according to another embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION

[0028] The invention can be used for the compression and / or expansion of a cycle fluid of a cryogenic refrigerator or liquefier, for example with a reverse Brayton cycle, commonly called turbo-Brayton, that is to say that it can be used in a cryogenic refrigerator or liquefier to compress and / or expand a cycle gas. Nevertheless, it goes without saying that the invention is applicable to any type of fluid treatment machine circulating or regulating a flow of fluid, as will be specified below.

[0029] Thus, with reference to figures 1 and 2, the machine according to the invention here comprises a casing 10 defining a first chamber or motor chamber 11, a second chamber or turbine chamber 12, and a third chamber or compressor chamber 13. The chambers 11, 12, 13 are aligned on the same axis called the motor axis 14.

[0030] The motor chamber 11 receives an electric motor stator 30. The motor chamber 11 is connected, by an inlet orifice 11.1 and an outlet orifice 11.2, to a first fluid circuit, or service circuit 80, allowing fluid to circulate in the motor chamber 11 in order to cool the electric motor. The service circuit 80 comprises, in a simplified manner, two lines 81, 82 and a heat exchange device 83: the first line 81 connects the inlet orifice 11.1 to the heat exchange device 83 and the second line 82 connects the outlet orifice 11.2 to the heat exchange device 83. The service circuit 80 may further comprise a circulation pump 84 mounted here on the first line. This structure will not be detailed further here, being known and without direct relation to the invention.

[0031] The turbine chamber 12 and the compressor chamber 13 each comprise a fluid inlet orifice 12.1, 13.1 and a fluid outlet orifice 12.2, 13.2 which are connected to a second fluid circuit, or treatment circuit 90. The treatment circuit 90 may comprise, in a simplified manner, four main lines 91, 92, 93, 94 and a heat exchange device 95: the first line 91 connects the inlet orifice 13.1 to the heat exchange device 95, the second line 92 connects the outlet orifice 13.2 to the heat exchange device 95, the third line 93 connects the inlet orifice 12.1 to the heat exchange device 95, the fourth line 94 connects the outlet orifice 12.2 to the heat exchange device 95. This structure will not be detailed further here, being known and without direct relation to the invention.

[0032] A shaft 20 is mounted in the casing 10 to extend into the stator 30 of the motor chamber 11: the shaft 20 is more precisely mounted to pivot in the casing 10 by means of two guide bearings 40, such as magnetic bearings, arranged for one in a bore 15 of the casing 10 separating the motor chamber 11 from the turbine chamber 12 and for the other in a bore 16 of the casing 10 separating the motor chamber 11 from the compressor chamber 13. The bores 15, 16 are aligned with the motor axis 14. The central part of the shaft 20, extending into the stator 30 of the motor chamber 11, is arranged, in a manner known per se, to form the rotor of the electric motor in such a way that, when the stator 30 is supplied with an electric current, the rotor of the electric motor, and therefore the shaft 20, is driven in rotation. The electric motor thus formed is coaxial with the shaft 20.Again, this structure will not be detailed here, being known and not directly related to the invention.

[0033] The shaft 20 extends into the bores 15, 16 and has a first end 21 projecting into the turbine chamber 12 and a second end 22 projecting into the compressor chamber 13. The first end 21 carries a turbine rotor or wheel 50 rotating in the turbine chamber 12 and the second end 22 carries a compressor rotor or wheel 60 rotating in the compressor chamber 13. The turbine rotor 50 and the compressor rotor 60 form rotating elements for cooperating with the fluid circulating in the treatment circuit 90 and which has been introduced into the turbine chamber 12 and into the compressor chamber 13 through the inlet 12.1, 13.1 respectively and discharged from the turbine chamber 12 and from the compressor chamber 13 through the outlet 12.2, 13.2 respectively.

[0034] The machine also comprises rotating joints 70, 70' formed at the bores 15, 16 separating the engine chamber 11 on the one hand from the turbine chamber 12 and on the other hand from the compressor chamber 13 to limit a transfer of fluid between these chambers.

[0035] Also referring to the, the rotating joint 70 comprises a first labyrinth section 70.1 and a second labyrinth section 70.2 which follow one another along the motor axis 14 and are each arranged on one side of an intermediate space 100 of annular shape.

[0036] Each labyrinth section 70.1, 70.2 comprises a first series of first projecting elements 71, of annular shape, integral with the wall of the bore 15 of the casing 10 or of the rotating shaft.

[0037] A tapping 101 is made in the casing 10 directly above the intermediate space 100 in order to constitute a fluid inlet / outlet orifice. The tapping 101 is here connected to a regulating device 102 making it possible to regulate the pressure in the intermediate space 100.

[0038] The rotating joint 70' has not been shown in detail but its structure may be identical to that of the rotating joint 70. A tapping 101' is made in the casing 10 directly above the intermediate space of the rotating joint 70' in order to constitute a fluid inlet / outlet orifice. The tapping 101' is here connected to a regulating device 102' making it possible to regulate the pressure in the intermediate space.

[0039] The service circuit 80 is arranged to maintain a first pressure P1 in the engine chamber 11 via the circulation pump 84; the turbine wheel 50 and the turbine chamber 12 are arranged to maintain a second pressure P2 in the turbine chamber 12 as a function of the rotational speed of the shaft 20; the compressor wheel 60 and the compressor chamber 13 are arranged to maintain a third pressure P3 in the compressor chamber 13 as a function of the rotational speed of the shaft 20.

[0040] The regulating device 102 ensures an evacuation of fluid from the intermediate space 100 of the rotating joint 70 or an injection of fluid into the intermediate space 100 in such a way that the pressure in said intermediate space 100 is substantially equal to the pressure P2.

[0041] More specifically, the regulating device 102 is arranged to regulate the pressure in the intermediate space 100 as a function of the difference between the pressure in the intermediate space 100 and the pressure P2.

[0042] With reference to the and according to a first embodiment, the regulation device 102 here comprises an electronic control circuit 1020 controlling on the one hand a first solenoid valve 1021 connecting the tapping 101 to a first pipe having a pressure lower than the pressure P2 (said pipe is here the line 91, whose gas comes from the outlet of the turbine chamber 12, but may be another line of the treatment circuit 90 or belong to another circuit, or simply be put to the exhaust), and, on the other hand a second solenoid valve 1022 connecting the tapping 101 to a second pipe having a pressure higher than the pressure P2 (here the line 92, whose gas will supply the turbine chamber 12 but which may be another line of the treatment circuit 90 or belong to another circuit).The electronic control circuit 1020 is connected to a pressure probe 103 (for example piezoelectric) for example mounted in the intermediate space 100 and measuring or determining the pressure to provide the electronic control circuit 1020 with an electrical signal I representative of the pressure in the intermediate space 100 and to a pressure probe 104 (for example piezoelectric) for example mounted in the turbine chamber 12 and measuring or determining the pressure to provide the electronic control circuit 1020 with an electrical signal II representative of the pressure in the turbine chamber 12: the pressure probes can therefore be arranged on either side of the labyrinth section 70.1 adjoining the turbine chamber 12.The electronic control circuit 1020 is arranged to open or close the solenoid valves 1021, 1022 so as to maintain the difference between the pressures in question at a value below a predetermined threshold, for example a few millibars. The electronic control circuit 1020 may comprise only analog components or also digital components such as a processor or a microcontroller, an FPGA, etc.

[0043] The regulating device 102' ensures an evacuation of fluid from the intermediate space 100 of the rotating joint 70' or an injection of fluid into the intermediate space of the rotating joint 70' in such a way that the pressure in said intermediate space is equal to a predetermined pressure.

[0044] The regulating device 102' has a structure identical to that of the regulating device 102. The electronic circuit is connected to a pressure probe, for example mounted in the intermediate space of the rotating joint 70' and measuring or determining the pressure to provide the electronic circuit with a signal representative of the pressure in the intermediate space 100 and to a pressure probe 205, for example mounted in the compressor chamber 13 and measuring or determining the pressure to provide the electronic circuit with a signal representative of the pressure in the compressor chamber 13: the pressure probes can therefore be arranged on either side of the labyrinth section adjoining the compressor chamber 13. The electronic circuit is arranged to open or close the solenoid valves so as to maintain the difference between the pressures in question at a value below a predetermined threshold.The solenoid valves are connected to a pipe at a pressure lower than the pressure that is to be maintained in the intermediate space 100 (here pipe 91) and to a pipe at a pressure higher than the pressure that is to be maintained in the intermediate space 100 (here pipe 92).

[0045] In the second embodiment shown in the, the solenoid valves 1021 and 1022 have been replaced by a single three-way solenoid valve 1023 connected to the tapping 101 and to the two lines 93, 94.

[0046] In the third embodiment shown in the, the solenoid valve 1022 remains but the solenoid valve 1021 has been replaced by a manual valve 1024.

[0047] In this particular embodiment, it is provided that the electronic control circuit 1020 comprises a manual control button for the solenoid valve 1022 to place the latter in the closed position and a screen displaying the pressure difference calculated from the information provided by the probes 103, 104 so as to allow manual adjustment of the manual valve 1024.

[0048] A reverse configuration is also possible, namely leaving the solenoid valve 1021 of the first embodiment and replacing the solenoid valve 1022 with a manual valve.

[0049] In the fourth embodiment shown in the, the pressure regulating device 102 comprises a mechanical regulator having a setpoint port connected to two tappings 105, 106 opening for one into the intermediate space 100 and for the other into the turbine chamber 12 and an inlet / outlet port for the regulated fluid which is connected to the tapping 101. In this embodiment, the regulating device 102 only allows fluid to be injected into the intermediate space 100 or extracted therefrom, except for providing a three-way valve or two valves allowing the regulator to be selectively connected to a pipe at a pressure higher than the desired pressure and to a pipe at a pressure lower than the desired pressure.

[0050] Such an arrangement makes it possible to maintain the pressure difference at a few tens of millibars.

[0051] Of course, the invention is not limited to the embodiments described but encompasses any variant falling within the scope of the invention as defined by the claims.

[0052] In particular, the machine may have a structure different from that described and for example: the machine may comprise only a motor and a compressor, or a motor and a turbine, or a compressor and a turbine; only one of the rotating joints may have the structure described here or one of the rotating joints may be in accordance with the first embodiment and the other rotating joint may be in accordance with the second embodiment; the rotating joint may comprise a different number of projecting elements; the rotating joint may comprise a first section and a second section having different structures (spacing and dimensions of the projecting elements for example); the projecting elements 71 may have a thickness which varies as one moves away from the motor axis 14;the dimensioning of the projecting elements 71 may be different from that described: the projecting elements 71 may have diameters increasing towards one end of the shaft (the shaft and the bore being stepped at the level of the rotating joint); the spacing between the projecting elements 71 may be constant in each series or vary along the length of the rotating joint; the bearings may be of a type other than those described and for example dynamic gas bearings; the number of bearings and / or the number of rotating joints may be different from those indicated;the compressor may have one or more stages: the compressor chamber and the compressor rotor may be staged and the second fluid circuit may comprise intermediate lines connecting the different stages of the compressor chamber to each other, the first fluid circuit may comprise secondary lines connecting each intermediate line to valves connected to the tapping 101' to enable the pressure at the inlet of the engine chamber to be modified;the shaft could not carry a turbine wheel and / or a compressor wheel but simply have an interface opposite a chamber, this interface being for example a surface subjected to the fluid of said chamber to balance axial forces exerted elsewhere on the shaft. There is shown a shaft 20 having a first end having an interface 20' which extends opposite the chamber 11 and which is formed of a face, transverse to the longitudinal axis of the shaft 20, subjected to the pressure of the fluid present in the chamber 11; the first fluid circuit or service circuit can be extremely rudimentary and only comprise a fluid inlet at the level of the rotating joint 70' adjoining the compressor chamber 13 (it is the leakage of fluid through this rotating joint 70' which supplies the engine chamber with fluid) and an outlet formed by the connection 101;the tappings 101, 101' may be offset relative to the intermediate space 100 and, for example, extend at an angle; the two regulating devices may have a structure different from that described and be purely manual to allow periodic manual adjustment based on pressure information. This is possible if the operating regime of the machine is stable, i.e. such that the same opening of the valve (or the same adjustment of the restriction member) makes it possible to achieve the regulation objective regardless of the speed of the machine; the machine may comprise a single differential pressure sensor connected on either side of the labyrinth; the first pressure sensor could be placed at the lips; the second could be placed in the turbine chamber and preferably as close as possible to the exit of the labyrinth;the sensors can be arranged directly in the chambers or in tappings opening into them; the pipe which brings the gas into the (or withdraws the gas from the) labyrinth can be used for pressure detection (one and the same pipe for both functions, the measurement is however less precise in this case); it is possible to combine at least two of the embodiments in the same regulation device, for example the second embodiment and the third embodiment; the casing can be in one or more parts; the casing in several parts can comprise, for example, only one or more joint planes transverse to the axis 14.;

Claims

A method of controlling a fluid treatment machine, comprising a casing (10) defining a first chamber (11) in which is mounted for pivoting a shaft (20) having an interface facing a second chamber (12), the first chamber being connected to a first fluid circuit (80) to maintain a first fluid pressure in the first chamber, the second chamber (12) being connected to a second fluid circuit (90) so that the interface is subjected to a fluid to be treated at a second pressure, the first chamber (11) being separated from the second chamber (12) by a rotating joint (70) comprising two labyrinth sections (70.1, 70.2) axially separated by an intermediate space (100) in which a third pressure prevails, characterized in that the method comprises the step of regulating the third pressure by taking as a setpoint a difference between the second pressure and the third pressure. Fluid treatment machine, comprising a housing (10) defining a first chamber (11) in which is mounted for pivoting a shaft (20) having an interface facing a second chamber (12), the first chamber being connected to a first fluid circuit (80) to maintain a first fluid pressure in the first chamber, the second chamber (12) being connected to a second fluid circuit (90) so that the interface is subjected to a fluid to be treated at a second pressure, the first chamber (11) being separated from the second chamber (12) by a rotating joint (70) comprising two labyrinth sections (70.1, 70.2) axially separated by an intermediate space (100) in which a third pressure prevails, the machine being characterized in that it comprises at least one pressure determining device (103, 104) determining the pressure in the intermediate space (100) and in the second chamber (12) which is connected to a pressure regulating device (102), the regulating device being connected to a tapping (101) opening into the intermediate space (100) and having as a setpoint a difference between the second pressure and the third pressure to maintain in said intermediate space (100) the third pressure substantially equal to the second pressure. Machine according to claim 2, in which the regulating device (102) comprises an electronic control circuit (1020) controlling at least one first solenoid valve (1021, 1023) and the determining device is connected to the electronic control circuit (1020) to provide it with an electrical signal representative of the pressure to which they are subjected. Machine according to claim 3, in which the first solenoid valve (1021) is connected to a pressure source lower than the second pressure and the regulating device (102) comprises a second solenoid valve (1022) connected to a pressure source higher than the second pressure. Machine according to claim 3, in which the first solenoid valve (1023) is a three-way solenoid valve connected to a pressure source lower than the second pressure and to a pressure source higher than the second pressure. Machine according to any one of claims 2 to 5, wherein the regulating device (102) comprises a manual valve (1024). Machine according to any one of claims 2 to 6, in which the interface is a rotating element. Machine according to claim 7, wherein the rotating element is a turbine wheel (50). Machine according to claim 7, wherein the rotating element is a compressor wheel (60). Machine according to any one of claims 2 to 9, in which the first chamber (11) receives a motor for driving the shaft (20), the motor (30) being coaxial with the shaft (20). Machine according to any one of claims 2 to 10, in which the determining device comprises two pressure probes mounted to be subjected to the pressure prevailing respectively in the second chamber and in a third chamber (13) and to provide the regulating device with an electrical signal representative of the pressure to which the two probes are subjected. Fluid treatment machine, according to claim 11 characterized in that it comprises: a first tap opening into the intermediate space (100) and a second tap opening into the second chamber (12); a pressure regulating device (102) having a setpoint port connected to the first tap and to the second tap and an inlet / outlet port connected to a third tap (101) opening into the intermediate space (100) to maintain in said intermediate space a third pressure substantially equal to the second pressure. Machine according to claim 12, in which the regulating device (102) is a pressure reducer. Machine according to claim 12 or 13, in which the interface is a rotating element. Machine according to claim 14, wherein the rotating element is a turbine wheel (50). Machine according to claim 14, wherein the rotating element is a compressor wheel (60). Machine according to any one of claims 12 to 16, in which the first chamber (11) receives a motor for driving the shaft (20), the motor (30) being coaxial with the shaft (20).

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