Secondary vein cavity surface between a fixed wheel and a moving wheel of an improved turbomachine

Abstract

One aspect of the invention relates to an assembly (E) of a turbomachine comprising: a stator including at least one fixed blade, an internal platform (31) including a central portion (310) extending radially from the fixed aerodynamic blade and two fixed deflectors (311) extending axially on either side of the central portion (310), a rotor including at least one drum (4) of revolution about the X-axis and a movable blade root, a cavity (5) of a secondary system delimited axially between the drum (4) and the internal platform (31), and radially between the roots of each movable blade (201, 202), characterized in that at least one of the surfaces delimiting the cavity (5) is a rough stabilizing surface having a roughness Ra greater than a surface of the fixed (30) or movable blades. Figure to be published with the abstract: Figure 1

Description

Title of the invention: Secondary flow cavity surface between a fixed wheel and a moving wheel of an improved turbomachine. TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of compressors and turbines of turbomachinery comprising successive moving and fixed wheels and cavities formed between each end of the stator wheel and the two successive moving wheels.

[0002] The present invention relates to the aerodynamic optimization of an axial stage of a turbomachine and, in particular, to reducing the impact of airflow in cavities on the performance of the main flow stream in compressors and turbines. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] Compressors and turbines of turbomachinery comprising successive moving wheels and fixed wheels alternately axially and cavities are formed between each end of the stator wheel and the two successive moving wheels surrounding it.

[0004] The moving and fixed wheels generally comprise blades forming a main channel of the primary airflow of the turbomachine, enabling the compression and expansion phases of the thermodynamic cycle. The compression phase, during the engine cycle, supplies energy to the airflow (compression), and the expansion phase allows the engine cycle to recover energy (expansion).

[0005] Part of the flow passes through the various cavities forming part of the secondary air system, also called the secondary stream. It is known that some of the energy losses (and therefore engine performance losses) of the turbomachine are due to the airflow in these cavities, as well as the interaction between the secondary and primary streams. Indeed, since each cavity is open to the primary stream, between the rotor and the stator, the secondary stream interacts with the airflow in the primary stream, thus impacting it and producing performance losses in the turbomachine. In fact, the airflow in the cavity modifies the air flow rate, changes the airflow angle at the leading edge of the rotors and stators, and produces internal vortices that are sometimes unstable and therefore a source of additional losses.

[0006] Geometric optimization solutions exist for the walls of the rotor and stators forming the cavity to reduce the impact of the airflow in the cavities on the main flow, in order to control and reduce losses within the cavity flow as well as losses due to interaction with the flow. main (control of incoming / outgoing flow rates, reduction of mixing losses, reduction of angle of attack alterations on downstream blades).

[0007] There is therefore a need to minimize the impact of secondary veins in order to optimize the airflow of the main vein and thus improve motor performance by reducing losses related in particular to instabilities in the cavities which are sources of unsteady phenomena. Summary of the invention

[0008] The invention offers a solution to the problems mentioned above, by allowing the flow to be stabilized in the cavities to reduce performance losses related to secondary flows.

[0009] One aspect of the invention relates to an assembly of a turbomachine comprising: • a stator comprising: • an external platform extending axially around an axis of rotation, • at least one fixed wheel extending radially from the external platform towards the axis of rotation, the fixed wheel comprising: • at least one fixed aerodynamic blade extending radially from the external platform towards the axis of rotation and • an internal platform comprising a central part extending radially from the fixed aerodynamic blade towards the axis of rotation and two fixed deflectors extending axially on either side of the central part, • a rotor comprising at least: • a drum of revolution around the X-axis, • two movable blades spaced axially by the drum, comprising: • an aerodynamic blade, the fixed blade being interposed between the two moving blades which together form a main channel of the primary airflow, • a foot comprising: i. a base coupled in rotation to the drum and ii. an external platform, comprising a movable deflector extending axially towards the corresponding fixed deflector, and radially from the movable blade towards the base, • a cavity of a secondary system delimited axially between the drum and the internal platform, and radially between the feet of each movable blade, characterized in that at least one of the surfaces delimiting the cavity is a rough stabilizing surface having a roughness Ra greater than a surface of fixed or moving blades.

[0010] Thanks to the invention, the cavities unexpectedly exhibit more stable flow by reducing losses related to internal vortices within the cavity, thus eliminating instabilities or decreasing the amplitude of unsteady variations. Indeed, increasing roughness generally works against reducing flow losses since it leads to fluid / rotor or stator surface friction losses, and therefore, the aim is generally to decrease surface roughness to reduce these friction losses. However, it has been observed that by increasing the roughness on portions or on the surfaces forming the cavity, the increase in friction losses is compensated by flow effects through an increase in the thickness of a zone near the surface (called the boundary layer), which improves flow stability.

[0011] Furthermore, such a modification can be carried out on rotor-stator assembly cavity surfaces already manufactured or in the process of being manufactured, since it does not require a change in the geometry of the rotor or stator but only a roughness treatment or even no treatment of one or more cavity surfaces undergoing a roughness reduction treatment.

[0012] In addition to the characteristics mentioned in the preceding paragraph, the rotor-stator assembly of a turbomachine according to one aspect of the invention may have one or more additional characteristics from among the following, considered individually or according to all technically possible combinations:

[0013] According to one embodiment, the roughness Ra of the rough stabilizing surface delimiting the cavity is two to fifteen times greater than that of the surface of the fixed or moving blades.

[0014] According to one embodiment, the rough stabilizing surface has a roughness greater than the surfaces of the fixed or moving blades.

[0015] According to one embodiment, each fixed deflector comprises an external surface extending axially on the side of the main vein of the primary airflow and an internal surface delimiting the cavity, the internal surface delimiting the cavity being a rough stabilizing surface having a roughness greater than the external surface of the fixed deflector.

[0016] According to one embodiment, each movable deflector comprises an external surface extending axially on the side of the main vein of the primary airflow and an internal surface delimiting the cavity, the internal surface delimiting the cavity being a rough stabilizing surface having a roughness greater than the external surface of the movable deflector.

[0017] According to one embodiment, each surface delimiting the cavity is a rough stabilization surface.

[0018] According to one embodiment, the rotor comprises at least two movable wheels, each comprising the movable blades, a disc comprising cells extending axially and distributed around the disc, each cell receiving the foot of one of the corresponding movable blades, and the fixed wheel comprises fixed blades aligned next to each other around the drum, between the movable blades of the two wheels, the cavity extending all around the drum and on one side of the discs between the feet of the movable blades.

[0019] According to one embodiment, the roughness of the rough Ra surface in the cavity is 2 to 15 times greater than that of the external surface of the rotor or stator platform.

[0020] This allows the rough surface to be in a transitionally rough regime, while the external surface of the platform is in a hydraulically smooth regime.

[0021] Another aspect of the invention relates to a compressor comprising a high-pressure stage and a low-pressure stage, in which one of the stages comprises an assembly according to the aspect of the invention described above with or without the different features of the embodiments described above.

[0022] Another aspect of the invention relates to a Low Pressure or High Pressure turbine comprising an assembly according to the aspect of the invention described above with or without the different characteristics of the embodiments described above.

[0023] Another aspect of the invention relates to a method of manufacturing the assembly according to the aspect of the invention described above with or without the different characteristics of the embodiments described above including a step of polishing the surfaces of the assembly except at least one rough stabilizing surface.

[0024] Another aspect of the invention relates to a method of manufacturing the assembly according to the aspect of the invention described above with or without the different characteristics of the embodiments described above including a step of sandblasting the roughness surface.

[0025] Another aspect of the invention relates to a method for manufacturing the assembly according to the aspect of the invention described above, with or without the various features of the embodiments described above, comprising a step of modeling the geometry of the assembly, characterized in that it includes a step of optimizing the flow by increasing the roughness of at least the surface rough stabilization. This modeling step can be carried out before either of the two steps of the two processes described previously.

[0026] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0027] The figures are presented for illustrative purposes only and are in no way limiting of the invention.

[0028] [Fig. 1] shows a schematic representation of an axial section of a part of a set of two movable wheels and one fixed wheel according to a first embodiment of the invention and an air flow in a cavity between the fixed wheel and the two movable wheels.

[0029] [Fig.2] shows a schematic representation of an axial section of the part of the assembly of two movable wheels and one fixed wheel according to a second embodiment of the invention and an air flow in a cavity between the fixed wheel and the two movable wheels. DETAILED DESCRIPTION

[0030] The figures are presented for illustrative purposes only and are in no way limiting of the invention.

[0031] The invention relates to an assembly E, E' of a turbine of a turbomachine comprising a stator and a rotor of a compressor and turbine.

[0032] Fig. 1 represents a schematic diagram of an axial section of assembly E according to an example of a first embodiment.

[0033] The stator of assembly E comprises an external platform 1 extending axially about an axis of rotation x and a fixed wheel 3 extending radially from the external platform 1 towards the axis of rotation. The stator may, of course, comprise several fixed wheels 3 aligned axially and spaced apart.

[0034] The fixed wheel 3 comprises fixed aerodynamic blades 30, each extending towards the axis of rotation x, only one of which is shown in the schematic diagram in [Fig. 1]. The fixed blades 30 are aligned and distributed circumferentially.

[0035] Each fixed wheel 3 comprises an internal platform 31 per fixed blade 30, only one of which is therefore visible in the schematic diagram of [Fig. 1]. The internal platform 31 comprises a central part 310 extending radially from the fixed aerodynamic blade 30 towards the axis of rotation X and two fixed deflectors 311 extending axially on either side of the central part 310.

[0036] The rotor comprises at least one drum 4 of revolution about the X-axis, comprising an external surface facing an internal surface of the central portion 310. The drum 4 is therefore in the same radial plane (intersecting the X-axis perpendicularly). The drum 4 can be coupled to drive or be driven by a non-rotating shaft represented. The assembly E therefore comprises a central chamber 50 between the internal surface of the central part 310 and the external surface of the drum 4.

[0037] The rotor comprises two movable wheels 2b 22> axially spaced from each other by the drum 4. Each movable wheel 2b 22 comprises a disc 25b 252 coupled to the drum 4 and movable blades arranged regularly around the disc 25b 252, of which one movable blade 20b 202 per wheel is shown in this schematic diagram. Furthermore, only a portion of each disc and a portion of the drum are shown in this schematic diagram. Each movable blade 20b 202 comprises a movable aerodynamic blade 211, 212> forming, with the fixed blade 30, a main duct of the primary airflow. The fixed blade 30 is located axially between the two movable blades 21b 212 of the two movable wheels 2b 22. Each movable blade 20b 202 comprises a foot comprising a base mounted in a recess of the corresponding disc.

[0038] Each foot further includes an external platform 22b 222, comprising a movable deflector 225b 2252, extending axially towards the corresponding fixed deflector 311, and radially from the movable blade 21b 212, towards the base.

[0039] The internal platform 31 comprises its central part 311 axially between the two feet of the two movable blades 20b 202. A gap is formed between each fixed deflector 311 and the movable deflector 225b 2252 allowing air to enter or exit a cavity 5. The cavity 5 comprises an upstream enclosure 53, and a downstream enclosure 54 as well as the central chamber 50 communicating between the upstream enclosure 53, and the downstream enclosure 54. These enclosures 53, 54 communicate with the main duct through the gaps which separate the internal platform 31 respectively from the movable platforms 22b 222.

[0040] Each enclosure 53, 54 is therefore formed between the internal platform 31 and the mobile platform 22b 222 the foot of the mobile blade 20b 202 and the drum 5.

[0041] In this embodiment, all surfaces forming the cavity 5 are rough stabilizing surfaces (represented by a thicker line) having a roughness greater than that of a surface of the fixed or movable blades, in this case, the surfaces of each movable and fixed wheel forming the main stream. Thus, each fixed deflector 311 comprises an internal surface delimiting the cavity 5 and an external axial surface opposite the internal axial surface on the side of the main stream, in which the internal axial surface delimiting the cavity 5 is a rough stabilizing surface and therefore rougher than that of the external surface of the fixed deflector 311.

[0042] According to an example of this embodiment, the assembly is part of the compressor and, generally, the external surface of the fixed deflector 311 as well as the fixed blade 30 comprises an arithmetic roughness Ra (i.e., a measured arithmetic mean height) between half a micron and one micron, for example 1 micron to achieve a hydraulically smooth regime. Thus, in this example of this embodiment, the surfaces delimiting cavity 5 have a roughness greater than two microns, for example, seven microns, allowing for a transitionally rough regime. This results in increased friction losses between the gas in cavity 5 and the surfaces delimiting it, increasing the thickness of a zone near the surface (called the boundary layer), producing flow effects that improve flow stability.

[0043] According to another example of this embodiment, the assembly is part of a turbine, for example a high pressure or low pressure turbine and generally the external surface of the fixed deflector 311 as well as the fixed blade 30 comprises a roughness Ra between one micron and three point five microns, for example 1 micron to be in a hydraulically smooth regime.

[0044] Fig. 2 represents a schematic diagram of an assembly E' according to an example of a second embodiment identical to the first embodiment except that in this second embodiment, only a part of the surfaces delimiting the cavity 5' are rough stabilizing surfaces.

[0045] The various features include the same references as those in [Fig. 1] except that those which have changed also include a “quotation mark”.

[0046] In this embodiment, only the internal axial surfaces of the movable deflectors 225' and 225' of the movable platforms 22' and the fixed deflectors 311' of the internal platform 31' delimiting the upstream 53' and downstream 54' enclosures, as well as the axial surface of the central part 310' delimiting the central path 50' of the cavity 5', are each a rough stabilizing surface. In other words, in this example, these rough stabilizing surfaces are 2 to 15 times rougher than the other surfaces delimiting the cavity 5' of this embodiment, the other surfaces being the radial surfaces of the cavity 5', as well as the axial surfaces of the drum 4'. The radial surfaces of the cavity 5' are the surface of each deflector (fixed or movable) 311', 225'i,225'2 forming the gap, those of the central part 31' and that of the foot of each movable blade 20 / .20 / .

[0047] Each movable wheel 2' i 2'2 therefore comprises in this example only the internal surface delimiting the cavity 5' of the platform 22\ 22'2.

[0048] According to another example not shown, only the radial surfaces of each deflector (fixed or movable) 311', 225'i, 225'2 forming the gap are rough stabilizing surfaces. Other examples not shown can thus be realized depending on the geometric shape of the cavity.

[0049] For example, the design process for an assembly E, E' according to one of the described embodiments includes, as already known, a modeling step of the geometry of the assembly, and according to this example of the invention a flow optimization step by increasing the roughness of one or more surfaces of the cavity 5, 5' until the flow stability in the cavity 5, 5' is improved or optimized and to identify and record each roughness value of each surface having increased roughness as a stabilizing rough surface.

[0050] The method of designing an assembly E, E' according to one of the described embodiments includes either during a polishing step, a masking of each rough stabilizing surface or a sandblasting or grinding step of each rough stabilizing surface to obtain a roughness greater than the other surfaces.

[0051] In these different examples of these different embodiments, the stability rough surfaces may have a different roughness value from each other, but these roughness values ​​are always greater than the roughness of the roughest surface of the main vein.

[0052] In these different examples of these different embodiments, the drum 4 may include a labyrinth opposite the internal surface of the central part 310 of the internal platform 31.

[0053] The assembly E, E' may be that of an upstream module comprising several axial compression stages of a compressor and / or a downstream module comprising a centrifugal compression stage. Each axial stage comprises a rotating wheel 2b 222' i2'2 and the corresponding disc, as well as a fixed wheel 3, 3'. The rotor discs are fixed coaxially to each other by a drum and to a wheel of the centrifugal stage, which is itself fixed by an internal cylindrical housing of the combustion chamber to at least one rotor wheel of the turbine. The turbine wheel may also be one of those of the assembly described above.

[0054] Unless otherwise specified, the same element appearing on different figures has a unique reference.

Claims

1. Demands Assembly (E, E') of a turbomachine comprising: - a stator comprising: • an external platform (1) extending axially around an axis of rotation (x), • at least one fixed wheel (3, 3') extending radially from the outer platform (1) towards the axis of rotation, the fixed wheel (3, 3') comprising:

1. at least one fixed aerodynamic blade (30) extending radially from the outer platform (1) towards the axis of rotation (x) and 2. an internal platform (31,31') comprising a central part (310, 310') extending radially from the fixed aerodynamic blade (30) towards the axis of rotation (X) and two fixed deflectors (311,311') extending axially on either side of the central part (310, 310'), in which each fixed deflector (311,311') comprises an external surface extending axially on the side of the main duct of the primary airflow and an internal surface delimiting the cavity (5, 5'), - a rotor comprising at least: • a drum (4) of revolution about the X axis, • two movable blades (20i, 20220'i 20'2) axially spaced by the drum (4), comprising: - a movable aerodynamic blade (211, 212>), the fixed blade (30) being interposed between the two movable blades (21 b 212.) together forming a main channel of the primary airflow, - a base comprising: i. a base coupled in rotation to the drum (4) to the drum and ii. an external platform (22b 222 22' i,22'2), comprising a movable deflector (225 b 225 222 25' i,225'2) extending axially towards the corresponding fixed deflector (311,311'), and radially from the movable blade (21 b 212) towards the base, - a cavity (5, 5') of a secondary system delimited axially between the drum (4, 4') and the internal platform (31, 31'), and radially between the feet of each movable blade (20b 202 20i' 202'), characterized in that the internal surface of the fixed deflector (311,311') delimiting the cavity (5, 5') is a rough stabilizing surface having a roughness greater than: • the external surface of the fixed deflector (311,311') • a surface of the fixed blades (30) or mobile (21 b 212).

2. Assembly (E, E') of a turbomachine according to the preceding claim, wherein the roughness Ra of the rough stabilizing surface delimiting the cavity (5, 5') is two to fifteen times greater than that of the surface of the fixed (30) or movable (211, 212) blades.

3. Assembly (E, E') according to any one of the preceding claims, wherein the stabilizing rough surface has a roughness greater than the surfaces of the fixed (30) or movable (211, 212, 211', 212') blades.

4. Assembly (E, E') according to any one of the preceding claims, wherein each movable deflector (225b 2252.225'i. 225'2) comprises an external surface extending axially from the side of the main duct of the primary airflow and an internal surface delimiting the cavity (5, 5'), the internal surface delimiting the cavity (5,5') being a rough stabilizing surface having a roughness greater than the external surface of the movable deflector (225b 2252,225 / , 2252') and a surface of the fixed (30) or movable (21b 212) blades.

5. Assembly (E) of a turbomachine according to any one of the preceding claims, wherein each surface delimiting the cavity (5) is a rough stabilizing surface.

6. Assembly (E, E') according to any one of the preceding claims, wherein the rotor comprises at least two movable wheels (2b 22, 2'i 2'2 ) each comprising the movable blades (20i, 202, 20i'_202'), a disk (25i, 252) comprising alveoli extending axially and distributed around the disk, each alveolus receiving the foot of one of the corresponding movable blades (20i, 202, 20i'_202') and the fixed wheel (3') comprising fixed blades (21b, 212, 211', 212') aligned next to each other around the drum, between the movable blades (20i, 202, 20i'_202') of the two wheels, the cavity (5) extending all around the drum (4) and on one side of the disks (25i, 252) between the feet of the movable blades (20i, 202, 20i'_202').

7. Compressor comprising a high-pressure stage and a low-pressure stage, wherein one of the stages comprises an assembly (E, E') according to any one of the preceding claims.

8. Low pressure or high pressure turbine comprising an assembly (E, E') according to any one of claims 1 to 6.

9. Method of manufacturing an assembly (E, E') according to any one of claims 1 to 6 comprising a step of polishing the surfaces of the assembly except for at least one rough stabilizing surface.

10. Method of manufacturing an assembly (E, E') according to any one of claims 1 to 6 comprising a step of sandblasting the roughness surface.

11. A method for designing an assembly (E, E') according to any one of claims 1 to 6 comprising a step of modeling the geometry of the assembly, characterized in that it includes a step of optimizing the flow by increasing the roughness of at least the rough stabilizing surface.

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