EP1473462B1 - Cartridge compressor unit - Google Patents

Description

The invention relates to a centrifugal compressor group or motor-compressor unit. More particularly, the invention relates to a centrifugal compressor group with vertical joint plane, that is to say a compressor unit whose compressor is closed by two end caps and composed of one or more compression sections placed online.

A particularly advantageous application of such a compressor unit concerns the production of an integrated compressor unit, that is to say a compressor unit which comprises an electric motor driving a rotor and a compressor comprising a set of at least one wheel with compression vanes disposed on a driven shaft driven by the rotor, the assembly being mounted in a gas-tight common housing handled by the compressor unit.

However, the invention generally applies to any compressor which may consist of a cartridge comprising a rotor supported by bearings and an aerodynamic stator provided with shaft end sealing means mounted in an envelope, these different components that may or may not bathe in the gas handled by the compressor.

Such compressors can be driven by all types of motor means, for example electric motor means fixed or variable speed, high speed or not, or by a steam turbine, a gas turbine, ... a speed multiplier or a mechanical speed variator that can be placed if necessary between the trainer and the compressor.

Referring to FIG. 1, a compressor of a conventional vertical gasket compressor unit conventionally comprises a generally cylindrical shell 10 provided with a bottom 12 inside which the different parts of the compressor are mounted, namely the rotor 14, the stator 16 of the part aerodynamic compressor, the shaft end sealing means 18 and 20, radial bearings, such as 21, and a pivot 22 providing axial guidance of the rotor 14 and constituting an abutment limiting the axial displacement of the rotor during compressor operation.

The assembly is closed by a cover 24 fixed on the casing 10, for example by screwing or by means of a shearing ring 26.

As regards the stator elements 16, these comprise an input cell 28 delimiting an intake duct 30 intended to supply the compressor with gas, and one or more diaphragms 29 intended to collect the gas at the outlet. of each paddle wheel, such as 30, to slow it down in a radial diffuser 31 and then guide it to the next wheel by a return channel 32. Finally, an outlet cell 34, which includes a discharge volute, provides the gas collection at the outlet of the last impeller of the compressor and the guide to a discharge pipe.

To ensure the tightness of the assembly, shaft end sealing devices 18 and 20 are respectively mounted in the bottom 12 of the casing 10 and in the cover 24.

In this arrangement, the axial forces generated by the pressure distribution inside the compressor, due to the implementation of the paddle wheels, put under tensile stress the stator fastening systems of the aerodynamic portion of the turbocharger. Indeed, the increase in pressure within each compression cell causes the appearance of forces within the radial diffuser and the return channel, tending to separate the cells. This is particularly the case with the volute and certain stator elements, but such forces are more and more applicable to the shaft end sealing devices and to the pivoting device 22.

Reference may also be made to DE-A-196 54 840, which describes a compressor unit comprising a rotor driven in rotation by motor means in a stator and several stages of compression each comprising a paddle wheel driven by the rotor. The assembly is mounted in a cartridge in an envelope.

The architecture of the compressor unit described in this document also does not allow to effectively compensate the axial forces generated by the rotation of the paddle wheels.

The object of the invention is to overcome the drawbacks of the state of the art and to provide a compressor unit, particularly of the type with a joint plane. to avoid the occurrence of forces on the mounting elements of the various components of the compressor and further facilitating the assembly and maintenance of such a compressor.

According to the invention, it is therefore proposed a compressor unit, comprising an electric motor driving a rotor, at least one compressor comprising a stator comprising, mounted in a cartridge in an envelope, at least one input cell delimiting an admission duct supply of the gas compressor unit, an outlet cell delimiting a discharge volute and at least one compression cell disposed between the intake duct and the outlet volute and each equipped with a compressor blade wheel mounted on a driven shaft driven by the rotor, a radial centering pivot forming a stop for the rotor and shaft end sealing means.

This compressor unit further comprises shaft end sealing means interposed between the rotor and the output cell.

Thus, the positioning of the shaft end sealing means between the output cell and the rotor makes it possible to establish fluid communication between the end face of the output cell and the discharge pipe, thus generating forces on this face opposing the forces generated under the effect of the pressure of the gas in each compression cell.

According to one embodiment, the output cell and a corresponding end of the casing comprise two facing radial surfaces through which the cartridge bears against the casing with clearance, said bores being made to be in fluid communication with the casing. output of the output cell.

For example, said radial surfaces opposite the exit cell and the envelope are each delimited by two end bores made in the output cell, on the one hand, and in said corresponding end of the envelope, 'somewhere else.

According to another characteristic of the compressor unit according to the invention, the latter comprises sealing elements adapted to achieve a seal between the cartridge and the envelope in an area encompassing the output of the output cell and said radial surfaces.

The sealing elements may be arranged to provide a seal between the intake duct and the compressor outlet and to establish fluid communication between a cavity defined by the facing surfaces and the outlet of the compressor.

In one embodiment of the compressor unit according to the invention, the shaft end sealing means are fixed on the cartridge.

According to another characteristic of the invention, the assembly constituted by the motor and the or each compressor is mounted in a common envelope to constitute an integrated motor compressor.

In this case, in one embodiment, the envelope comprises a first section in which the motor is arranged and a second section in which the compressor is mounted, the first and second sections being separated by a narrowed section bore delimiting said surface. radial of the envelope.

The output cell comprises, for example, an axial cylindrical extension which fits into said bore, with the interposition of a sealing element.

• la figure 1, dont il a déjà été fait mention, illustre la structure générale d'un ensemble turbocompresseur selon l'état de la technique ;
• la figure 2 est une vue en coupe d'un compresseur de groupe compresseur conforme à l'invention ;et
• la figure 3 illustre un autre exemple de réalisation d'un compresseur de groupe compresseur conforme à l'invention.

Other objects, features and advantages of the invention will appear on reading the following description, given solely by way of nonlimiting example, and with reference to the appended drawings in which:

• Figure 1, which has already been mentioned, illustrates the general structure of a turbocharger assembly according to the state of the art;
• FIG. 2 is a sectional view of a compressor unit compressor according to the invention, and
• FIG. 3 illustrates another embodiment of a compressor unit compressor according to the invention.

FIG. 2 shows a sectional view of a compressor of a compressor unit according to the invention, designated by the general reference numeral 36. As can be seen in this figure, this compressor 36 is constituted by a compressor multi-stage centrifuge with a vertical joint plane, that is to say closed by an end cap, and is composed of several compression sections arranged in line between an inlet E for supplying the compressor with gas to be compressed and an output S of compressed gas. It is intended to be associated with an electric motor (not shown) driving in rotation a drive shaft driving itself a rotor 38. This electric motor can be a fixed or variable speed motor, high speed or not. The rotor 38 can also be rotated by a steam turbine or a gas turbine. It will also be noted that a multiplier or a mechanical speed variator may be interposed, as the case may be between the compressor 36 and the motor means.

As seen in this Figure 2, the compressor 36 essentially comprises a casing 40 of generally cylindrical shape inside which are placed a set of compression cells 42, 44, 46 and 48 which each constitute a compression stage. These compression cells 42, 44, 46 and 48 are arranged in line between an input cell 50 in which is formed an intake duct 52 for supplying the compression stages and an output cell 54 delimiting a volute of repression 56.

The intake duct 52 is arranged coaxially with an orifice 58 formed in the casing 40 to form the gas inlet E. The outlet volute 56 opens, meanwhile, into an orifice 60 formed in the casing 40 to form the outlet S of compressed gas. Each compression cell 42, 44, 46, and 48 comprises a blade wheel, such as 62, rotated by the rotor 38 and providing, as is conventional, on the one hand, an increase in the static pressure of the gas handled by the compressor and, on the other hand, an increase in kinetic energy. A radial diffuser 64, fitted to each compression cell, performs a pressure transformation of the kinetic energy increase downstream of the impeller 62. A fuel return channel 66 guides the gas to a next stage or to the output volute 56.

FIG. 2 also shows that the envelope 40 is provided with a first open end 68 closed by an end cap 70 fastened by means of shear rings 72 or bolted and an opposite end 74 which has a section bore narrowed relative to the remainder of the casing, into which an axial cylindrical extension 76 of the outlet cell 54 is inserted.

On the side of the end 74, which is turned towards the motor means, the rotor 38 is guided radially by means of radial bearings 78. On the opposite side, that is to say on the open end side, a pivoting 80 having an axial stop 82 and radial bearings 84, maintains the radial and axial positioning of the rotor 38.

Finally, shaft end sealing devices 86 and 88 are arranged, one between the rotor 38 and the input cell 50 and the other between the rotor 38 and the output cell 54, particular between the rotor 38 and the axial cylindrical extension 76.

According to one characteristic of the invention, the various elements involved in constituting the stator, namely the different compression stages as well as the input and output cells 54, are arranged in the envelope with insertion set , so as to allow axial sliding of these elements with respect to the envelope 40.

As can be seen in FIG. 2, the external peripheral surface of the outlet cell 54 delimits, with the external peripheral surface of the axial cylindrical extension 76, an annular surface S1, which bears, during assembly, against a surface corresponding annulus S2, delimited by a first bore 90 or main bore of the casing 40 and a second bore 92 delimiting the passage in which is inserted the axial cylindrical extension 76 of the output cell 54.

In particular, because of the set of insertion of the stator elements in the envelope 40, the space delimited by the two facing surfaces S1 and S2 is in fluid communication with the output volute 56 and is therefore at the pressure of the gas in turbocharger outlet.

Furthermore, first and second annular seal seals 92 and 94 are disposed on either side of the intake duct 52. A third annular seal 96 is interposed between the axial cylindrical extension 76 and the casing. 40. As a result, the gas leaving the turbocharger is confined between the second and the third gasket.

As it is conceivable, because of the pressure in the cavity defined by the facing surfaces S1 and S2, the pressure difference between the discharge S and the suction E of the compressor generates a force on the surface S1 directed according to the arrow F, that is to say directed towards the stop 82. Such a force makes it possible to maintain all the internal and static elements of the compressor between them.

In addition, the axial forces passing through the cartridge at the abutment 82 are much greater than the axial thrust of the rotor under the effect of the compression wheels 62, which contributes to ensuring the axial retention of the stator of the abutment.

Note that the output cell 54 is directly supported and held against the last compression stage due to the pressure in the cavity between the surfaces S1 and S2. This allows to precisely control the section of the radial diffuser 66 of the last stage which is located between these two elements. Thus, contrary to the state of the art in which the pressure in this diffuser results in a separation of the last compression stage and the output cell 54, and therefore the appearance of instability aerodynamic in the gas flow at the outlet of the diffuser generating rotating forces on the rotor and significant vibrations in the latter, no variation in section appears within the diffuser of the last stage.

It will also be noted that the shaft end sealing devices 86 and 88 as well as the radial bearings 78 and 84 are not subjected to any axial force and can therefore be fixed to the stator elements that are mounted in the envelope 40. to form a cartridge formed of a one-piece and rigid assembly, without the need for overdimensions. Such a cartridge can thus form a unitary assembly that can be easily inserted into the envelope without requiring a separate assembly of each element.

This is also the case of the fastening means used for mounting different stator elements, which do not require any particular oversizing and which therefore have as their main function to maintain these elements to create a unitary unit in the form of a homogeneous cartridge for be mounted in the envelope 40 during a single assembly operation.

Another embodiment of a compressor compressor according to the invention will now be described with reference to FIG. In this figure, elements identical to those described with reference to Figure 2 bear the same reference numerals.

This embodiment is suitable for producing an integrated motor compressor, that is to say a compressor unit in which the motor and the compressor are arranged in the same common envelope.

This figure shows the envelope 40, in which the input 50 and output 54 cells are arranged, as well as the compression cells 42, 44, 46 and 48 between a gas inlet E and an outlet S.

In the embodiment shown in this FIG. 3, the envelope 40 has a first section 98 in which is disposed the compressor 36, and a second section 100, in which is arranged the electric motor of the compressor unit (not shown), these two sections 98 and 100 being separated by an intermediate portion 102 of narrowed section defining an axial cylindrical passage and comprising, on the side facing the first section 98, an annular surface S2 intended to cooperate with the annular surface S1 of the output cell 54.

As is apparent from this FIG. 3, the construction and assembly of the compressor 36 are identical to those described above with reference to FIG. 2. Thus, this section 98 is also closed by an end cap 70 supporting the pivoting element 80. Likewise, on the opposite side, the radial bearings 78 are supported by the axial cylindrical extension 76 of the outlet cell 54. As in the embodiment previously described, this arrangement makes it possible to create between the suction and the discharge, and in particular between the suction and the cavity delimited by the facing surfaces S1 and S2 a pressure difference allowing a maintenance of all the internal elements of the compressor between them and to limit accordingly the forces on the sealing devices and on the bearings and swivel fitted to the compressor.

Note that this type of configuration is applicable to both a compressor having an axial stop on the side of the drive means on the opposite side.

It also applies to a compressor having several sections in line.

As it is conceivable, the invention which has just been described makes it possible to keep all the compressor parts in contact with each other because of the forces generated by the pressure of the gas filling the cavity between the surfaces S1 and S2 of the outlet cavity, on the one hand, and the envelope, on the other hand.

In addition, as indicated above, the mounting of the volute on the last diffuser can control the section of this diffuser, thus avoiding any risk of aerodynamic instability at low flow.

In addition, no screw, stud or bolt or other connecting means is subjected to tensile stresses to maintain the parts together when the machine is in operation. Such an advantage is particularly beneficial when the turbocharger manipulates a wet or corrosive gas, which greatly improves its reliability. The arrangement according to the invention also ensures a high rigidity of the cartridge, especially as the pressure inside the compressor is high.

Finally, the invention makes it possible to greatly facilitate the assembly of the compressor and to reduce the intervention time of the maintenance personnel.

Claims (8)

1. Compressor unit comprising an electric motor driving a rotor (38), at least one compressor (36) comprising a stator including, mounted in a cartridge within a casing, at least one inlet cell (50) delimiting an intake duct (52) for supplying the suppressor unit with gas, one outlet cell (54) delimiting a delivery volute and at least one compression cell (42, 44, 46, 48) positioned between the intake duct and the delivery volute and each equipped with a compression impeller (62) mounted on a driven shaft driven by the rotor, a set of supports (80) for radial centring, forming a thrust bearing for the rotor and shaft end sealing means (86, 88) inserted between the rotor (38) and the outlet cell (54), characterized in that the outlet cell and a corresponding end of the casing comprise two radial surfaces (S1, S2) facing each other and by which the cartridge bears against the casing with clearance, the said bores being made in such a way as to be in fluidic communication with the outlet (S) of the outlet cell.
2. Compressor unit according to Claim 1, characterized in that the said radial surfaces (S1, S2) facing each other belonging to the outlet cell and to the casing are each delimited by two end bores made in the outlet cell, on the one hand, and in the said corresponding end of the casing, on the other hand.
3. Compressor unit according to one of Claims 1 and 2, characterized in that it comprises sealing elements (94, 96) designed to perform sealing between the cartridge and the casing in a zone encompassing the outlet of the outlet cell and the said radial surfaces.
4. Compressor unit according to Claim 3, characterized in that the sealing elements are positioned in such a way as to establish sealing between the intake duct and the outlet of the compressor and as to establish fluidic communication between a cavity delimited by the facing surfaces (S1, S2) and the outlet of the compressor.
5. Compressor unit according to any one of Claims 1 to 4, characterized in that the shaft end sealing means are fixed to the cartridge.
6. Compressor unit according to any one of Claims 1 to 5, characterized in that the assembly made up of the motor and the or each compressor is mounted in a common casing (40).
7. Compressor unit according to Claim 6 dependent on Claim 1, characterized in that the casing comprises a first section (98) in which the motor is positioned and a second section (100) in which the compressor is mounted, the first and second sections being separated by a bore (102) of narrowed cross section delimiting the said radial surface of the casing.
8. Compressor unit according to Claim 7, characterized in that the outlet cell comprises an axial cylindrical extension (76) which can be inserted in the said bore with the interposition of a sealing element.

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