Axial Turbomachine Compressor Drum with Dual Means of Blade Fixing

Abstract

The present application relates to a rotor drum of a low-pressure compressor of an axial turbomachine. The drum includes a wall generally symmetrical in revolution about an axis and following a generally curved profile. The wall is configured to support a plurality of blade rows. A first blade row is formed by an annular platform integrally formed with the wall at the peak of its profile in relation to the axis; and a second blade row directly downstream of the first; and a third blade row directly upstream of the first; are formed by one or more blade-retaining grooves formed on the wall. The first blade row and the drum form an integral assembly, eliminating certain vibrations. Anchoring the blades is hybrid or mixed. The rotor may be mounted in a housing with ring-shaped stators.

Description

This application claims priority under 35 U.S.C. §119 to European Patent Application No. 13173510.2, filed 25 Jun. 2013, titled “Axial Turbomachine Compressor Drum with Dual Means of Blade Fixing,” which is incorporated herein by reference for all purposes.

BACKGROUND

1. Field of the Application

The present application relates to a rotor of an axial turbomachine. More specifically the present application relates to a rotor drum of an axial turbomachine compressor. The present application relates to an axial turbomachine fitted with a low-pressure compressor rotor drum.

2. Description of Related Art

A turbomachine enables a gas to be compressed, burnt and expanded. By this means the turbomachine provides mechanical energy. To perform these steps, the turbomachine comprises a compressor and a turbine which are fitted with a rotor and a housing.

The inner surface of the housing and the outer surface of the rotor define the contours of the primary flow path. It has variations in its annular section. Its inner and outer contours can increase and decrease in diameter along the axis of the engine. In a compressor, especially a low-pressure one, the outer housing typically has a reduced diameter downstream. Moving from upstream to downstream, the diameter of the rotor may increase and then decrease. This combination of surfaces enables a wide inlet area and a high compression ratio at the output.

To transmit mechanical work to the fluid, the housing and the compressor rotor each comprise a plurality of annular rows of blades. The rotor blade rows and the stator blade rows alternate axially.

The housing may include a plurality of annular stators each comprising an annular blade row. The stators form rings which abut each other axially for the purpose of assembling them. In this case, each blade in the rotor row is attached to the rotor via a root inserted in an annular groove formed on the rotor.

During assembly of a compressor with a drum-shaped rotor, a first blade row is mounted on the rotor and then a stator is assembled axially facing this first row. Only then can a second blade row be mounted on the rotor after the stator relative to the first row. Assembly thus continues onwards, assembling a rotor blade row and a stator, one after the other. This mode of assembly is required by the fact that the stators being made in one piece and their inner diameters do not allow the rotor with its blades to be inserted.

Patent FR 2845436 B1 discloses an axial turbomachine compressor. The compressor comprises an outer housing formed of several stators assembled axially. It also comprises annular rows of blades which are each located between the stators. The rotor blades are fixed by means of roots that are inserted into annular grooves formed in the rotor. This embodiment makes it possible to produce a compressor that is simple to assemble. However, the rotor is subject to vibrations. It develops complex vibrational modes that are difficult to analyse and damp. Moreover, its implementation requires complex and expensive machining. In addition, its structure is massive and heavy.

Although great strides have been made in the area of axial turbomachines, many shortcomings remain.

DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an axial turbomachine in accordance with the present application.

FIG. 2 shows a diagram of a turbomachine compressor according to the present application.

FIG. 3 illustrates a section of the rotor drum according to the present application.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present application aims to solve at least one of the problems present in the prior art. More particularly, the present application aims to reduce the vibrations in an axial turbomachine rotor. The present application also aims to lighten the rotor of an axial turbomachine.

The present application relates to a rotor drum of an axial turbomachine, in particular of a low-pressure compressor, the drum comprising a wall generally symmetrical in revolution about its axis and having a generally curved profile, the said wall being designed to support multiple rows of blades; wherein a first blade row is formed by an annular platform formed integrally with the wall at the peak of its profile with respect to the axis; and at least one, preferably every, second blade row directly downstream of the first and a third blade row immediately upstream of the first, is formed by one or more blade-retaining grooves formed on the wall.

According to an advantageous embodiment of the present application, the outer surface of the retaining groove(s) is an average distance from the axis which is less than the average distance of the platform from the first row to the said axis.

According to an advantageous embodiment of the present application, the wall comprises on its outer surface a set of annular ribs designed to mate with an annular layer of abradable material so as to provide a seal, the set of annular ribs being located axially between the first and second blade rows and/or between the first and third blade rows.

According to an advantageous embodiment of the present application, the minimum distance of the peaks of one set of ribs with respect to the axis is greater than the maximum distance from the said axis to the outer surface of the adjacent retaining grooves. It is the groove(s) of the second and/or third row blade row(s).

According to an advantageous embodiment of the present application, the blades of the first row are welded to the platform of the said row.

According to an advantageous embodiment of the present application, the platform of the first blade row comprises blade stubs on which are welded blade extensions; preferably the height of the blade stubs is more than 10% of the radial height of the blades in the first row, more preferably more than 25%.

According to an advantageous embodiment of the present application, the blades of the first row are at least partially cut into the body of the unmachined drum.

According to an advantageous embodiment of the present application, the general curved profile of the wall extends over most of the length of the drum and/or has a main concavity directed towards the main axis and extending over the major part of the length of the drum, the said profile having a radius relative to the axis which is at a maximum at the first blade row.

According to an advantageous embodiment of the present application, the platform of the first blade row is raised relative to the wall directly upstream and downstream of the said row.

According to an advantageous embodiment of the present application, the wall comprises two parts extending generally radially under the platform of the first row, so that the longitudinal section of the wall at the said platform has a π-shaped profile.

According to an advantageous embodiment of the present application, the wall comprises at least one annular stiffener extending radially inwardly at the first blade row, preferably in the extension of at least one of the radial parts.

According to an advantageous embodiment of the present application, the wall directly upstream and downstream of the first row comprises a part with substantially constant thickness which defines an annular space for housing a stator inner shell.

According to an advantageous embodiment of the present application, the rotor drum comprises blades of the second and/or third blade row, each of the said blades comprising a root housed in the, or a, retaining groove.

According to an advantageous embodiment of the present application, the retaining groove(s) is/are annular along the perimeter of the drum.

According to an advantageous embodiment of the present application, the blades in the first row and the annular platform form an integral unit.

According to an advantageous embodiment of the present application, the drum is made of a metallic material, preferably titanium.

According to an advantageous embodiment of the present application, the wall is forged and machined from solid.

According to yet another advantageous embodiment of the present application, the annular platform and the retaining grooves are integral.

According to an advantageous embodiment of the present application, the drum shows material continuity between the first row blades and the wall.

According to an advantageous embodiment of the present application, a set of annular ribs is distributed axially over the annular junction.

According to an advantageous embodiment of the present application, all the drum blade rows, except the first, comprise a blade-retaining groove for the purpose of assembling them on the drum.

The present application also relates to an axial turbomachine comprising a rotor drum, wherein the drum is in accordance with the present application; preferably the rotor is a low-pressure compressor rotor comprising essentially three annular rotor blade rows.

The present application also aims to reduce the vibrations of an axial turbomachine rotor. To achieve this, it removes any freedom of movement between the annular wall and the blades in the first row. The present application also improves the overall rigidity of the drum. The proposed architecture also enables the rotor to be lightened, affecting both the drum and the blades.

Machining the surfaces of the drum and the blades is simplified. All of these improvements to the drum are possible while maintaining the compatibility of the rotor with a housing formed of annular stators.

The present application is applied to a drum provided with annular ribs used as a means of sealing between the compression stages. This aspect is not limiting since the present application may also be applied to a drum mating with axial brush seals. Such seals are well known to those skilled in the art and may, for example, correspond to those disclosed in Patent DE 102005042272 A1.

In the following description, the terms inner or internal and outer or external refer to a position relative to the axis of rotation of the axial turbomachine.

FIG. 1 shows a schematic view of an axial turbomachine. In this case it is a double-flow turbojet. The turbojet 2 comprises a first compression stage, a so-called low-pressure compressor 4, a second compression stage, a so-called high-pressure compressor 6, a combustion chamber 8 and one or more turbine stages 10. In operation, the mechanical power of the turbine 10 is transmitted through the central shaft to the rotor 12 and drives the two compressors 4 and 6. Reduction mechanisms may increase the speed of rotation transmitted to the compressors. Alternatively, the different turbine stages can each be in communication with the compressor stages through concentric shafts. These latter comprise several rotor blade rows associated with stator blade rows. The rotation of the rotor around its axis of rotation 14 generates a flow of air and gradually compresses it up to the inlet of the combustion chamber 10.

An inlet fan, commonly designated a fan 16, is coupled to the rotor 12 and generates an airflow which is divided into a primary flow 18 passing through the various above-mentioned levels of the turbomachine, and a secondary flow 20 passing through an annular conduit (shown in part) along the length of the machine which then rejoins the main flow at the turbine outlet. The primary flow 18 and secondary flow 20 are annular flows and are channeled through the turbomachine's housing. To this end, the housing has cylindrical walls or shells that can be internal or external.

FIG. 2 is a sectional view of a compressor of an axial turbomachine 2 such as that shown in FIG. 1. The compressor may be a low-pressure compressor 4. The teaching of the present application may also be applied to the rotor drum of a turbine 10.

A splitter nose 22 of the primary 18 and secondary 20 airflows can be seen on the compressor 4. The rotor 12 comprises a plurality of annular rotor blade rows; in the case of FIG. 2 there are three. Further blade rows can be provided for. These three rows are axially consecutive. There is a first row of rotor blades 24, a second row of rotor blades 26 downstream of the first row 24 and a third row of rotor blades 28 upstream of the first row 24.

The rotor blades (24, 26, 28) spread out substantially radially from the rotor 12. The blades in one row are regularly spaced from each other, and have the same angular orientation to the airflow. Optionally, the spacing between the blades can vary locally as can their angular orientation. Some blades in a row may be different from the rest.

The compressor 4 comprises an external housing. The outer housing comprises several stators, for example four, which each comprise an outer shell 30, a stator blade row 32 and, optionally, an inner shell 34. An annular layer of abradable material 36 may be applied to the inside of the outer shell and the inner shell of a stator. The stator blades 32 of the same stator extend radially from their outer shell 30 towards their inner shell 34. The stators form closed circular rings. They are assembled axially against each other and fixed to each other by means of radial flanges 38.

The stators are associated with the fan or a row of rotor blades (24, 26, 28) for straightening the airflow so as to convert the speed of the flow into pressure.

The rotor 12 comprises a drum 40. The drum 40 has a wall 42 generally symmetrical in revolution about its axis of rotation 14, which axis is common with that of the turbomachine. The wall 42 may have an overall profile of revolution or the average profile of revolution about the axis of rotation 14. The general profile can be included in the thickness of the parts of the wall 42 that are axially at right angles to the stator blade rows.

The general profile is basically curved and may have a continuous curvature and/or continuously varying curvature. Radially it matches the variation in the inner surface of the primary flow 18. The exterior of the general profile is convex. Going from upstream to downstream the radius of the inner surface increases and then decreases, so that the profile of the wall has a maximum. The wall 42 is basically thin. Its thickness is generally constant. Its thickness is less than 10.00 mm, preferably less than 5.00 mm, more preferably less than 2.00 mm. The wall 42 forms a hollow body which defines a cavity having a shape of an ogive or keg. The drum 40 and/or the rotor blades (24, 26, 28) are made of a metallic material, preferably titanium.

The drum 40 comprises annular ribs 44 or lip seals. They form narrow annular strips which extend radially. They are designed to mate abrasively with annular layers of abradable material 36 on a stator so as to provide a seal. Generally, one abradable layer 36 mates with two annular ribs 44.

FIG. 3 is a detailed sectional view of the drum 40 of FIG. 2. The drum can also be a rotor drum of a high-pressure compressor. It can possibly also be a turbine rotor drum.

The first blade row 24 is integrally formed on the wall by an annular platform 46. The annular platform 46 is integrally formed with the wall 42. The annular platform 46 is formed atop the profile of the wall 42. The annular platform 46 has a profile of revolution generally straight or substantially curved.

The rotor blades 26 of the second row and the third row 28 each include a blade platform 48 defining the inside of the primary flow, a blade 50 extending radially outwardly from the blade platform 48, and a retaining root 52 extending radially inwardly from the blade platform 48. The retaining root 52 may be dovetailed. It may have a form whose axial dimension increases as it gets closer to the inside, enabling it to lock in place.

The wall 42 of the drum 40 comprises two zones for fixing blades using retaining grooves. The fixing zones each comprise an annular groove 54 into which the retaining roots 52 of the second-row blades 26 and the third-row blades 28 are inserted. The annular grooves 54 comprise annular outer surfaces which come into contact with the blade platforms 48. The blade platforms 48 of the second blade row 26 engage with the second outer surface 56, and the blade platforms 48 of the third blade row 28 engage with the third outer surface 58.

The retaining roots 52 generally have a shape matching the corresponding retaining groove so as to ensure radial retention. The retaining grooves 54 have a profile with a constriction at their outer face. Thus, the second row blades 26 and the third row blades 28 are retained reversibly. Mechanical clearance is provided between the annular wall 42 and the rotor blades of the second and third rows, so as to allow slight movement of the blades. However, the rotor is designed so that the centrifugal forces present during the compressor's operation force the blades into position in their throats.

According to an alternative of the present application, the retaining grooves can be axial grooves. The annular wall then comprises an annular row of axial grooves distributed over its circumference, and which each form an annular blade row.

The outer surface (56, 58) of at least one of the annular grooves 48 is at an average distance from the axis 14 which is less than the mean distance between the annular platform 46 and the first row 24 of the said axis. Preferably, each radius at an axial end of the annular platform 48 is greater than the maximum radius of the outer surface (56, 58) located opposite.

The first row blades 24 are anchored to the drum in a different manner from those of the other rows (26, 28). The blade retention or attachment is heterogeneous or hybrid. The first row blades 24 are fixed by welding to the annular platform 46. They may be welded by friction, for example by a process of orbital welding. The drum 40 thus serves as a support for fixing both types of blades.

For this purpose, the blades corresponding to the first row 24 are attached to a bare drum and welded to the annular platform 46. These blades can be directly or indirectly fitted onto the annular platform 46. The annular platform 46 may include blade stubs 60 extending radially from its outer surface. In this case, each blade which is welded to the second surface effectively forms a radial portion of the final blade. The weld 62 between a stub and a blade portion is set above the annular platform 46.

According to an alternative of the present application, the first row blades 24 can be integrally machined into the body of the unmachined drum in which the wall is also machined.

Thus, the wall of the drum 40 and the first row blades form an integral unit. They show continuity of material. Their metallic materials have crystalline continuity at their interface. They can, at least partially, be formed integrally. Anchoring the blades is irreversible. The first row blades 24 are integral with the annular wall 42. This embodiment eliminates vibration between the first row blades 24 and the wall 42 of the drum 40.

In addition, this method of anchoring the blades simplifies the machining to be carried out because the annular platform 46 and any stubs 60 are simpler to produce than an annular groove or a plurality of axial grooves. Indeed, a groove must be cut in a generally inaccessible space with a small tool, which increases the manufacturing time. Alternatively, an axial groove can be machined by broaching. However, this method for removing material requires expensive tooling and is not suitable for all types of drum.

The wall 42 of the drum immediately upstream and downstream of the first blade row 24 comprises at least a part 64 of substantially constant thickness or an axial annular join 64, with preferably two parts of substantially constant thickness 64. Each constant thickness part 64 extends axially from the annular platform 46 to the second blade row 26 or to the third blade row 28. The annular platform 46 is radially set out from the constant thickness part 64. The constant thickness parts 64 define an annular space between the first blade row 24 and the second blade row 26 or the third blade row 28, the annular spaces being radially open outwards. They are designed to accommodate the internal stator shells.

The wall 42 comprises two parts 65 which extend generally radially. They extend from the annular platform 46 inwardly. They may be located at each one of the axial edges of the annular platform 46. Thus, the wall may have a generally π-shaped profile. The profiles of the radial portions extend generally perpendicular to the profile of the annular platform 46.

The annular ribs 44 are located on the constant thickness parts 64. Each set of ribs comprises a plurality of ribs 44. On each side of the annular platform 46 there are progressive decreases in the external radii from an edge of an annular platform 46, ribs 44, and outer surfaces (56, 58) of the annular grooves. The peaks of these elements form a staircase. This configuration enables bladed stators to be fixed on both sides of the first blade row 24, and then the second row 26 and the third row 28 to be assembled.

FIG. 3 shows the blades 32 and the inner shell 36 of the two stators upstream and downstream, respectively, of the first blade row 24. FIG. 3 also illustrates with dashed lines these stators in an intermediate position during axial assembly around the drum.

The annular wall 42 of the drum includes annular stiffeners 66. The annular stiffeners 66 may include annular flanges which extend radially inwardly. These flanges are located axially at the ends of the annular platform 46, preferably in the radial extension of the radial portions 65.

The drum is usually machined by turning starting from an unmachined drum-shaped blank of which the walls include the finished drum. The drum blank must radially encompass the outer surfaces of the annular grooves 54, the annular platform 46, the internal stiffeners 66, and any blade stubs 60. Depending on circumstances, it may include the first blade row 24 along the entirety of their radial height.

Claims

1. A rotor drum of an axial turbomachine, comprising:

a wall generally symmetrical in revolution about an axis thereof and having a generally curved profile, the wall being configured to support a plurality of blade rows;

a first blade row formed by an annular platform integrally formed with the wall at a peak of the profile thereof in relation to the axis; and

at least one second blade row directly downstream of the first blade row and a third blade row directly upstream of the first blade row, the second blade row being formed by one or more blade-retaining grooves formed on the wall.

2. The rotor drum in accordance with claim 1, wherein the outer surfaces of the retaining grooves are at an average distance from the axis which is less than the average distance from the platform of the first row to the axis.

3. The rotor drum in accordance with claim 1, wherein the wall comprises:

a set of annular ribs on the outer surface of the wall configured to mate with an annular layer of abradable material, so as to provide a seal, the set of annular ribs being located axially between the first blade row and the second blade row and between the first blade row and the third blade row.

4. The rotor drum in accordance with claim 1, wherein the wall comprises:

a set of annular ribs on the outer surface of the wall configured to mate with an annular layer of abradable material, so as to provide a seal, the set of annular ribs being located axially between the first blade row and the second blade row or between the first blade row and the third blade row.

5. The rotor drum in accordance with claim 3, wherein the minimum distance of the peaks of one set of ribs relative to the axis is greater than the maximum distance from the axis of the outer surfaces of the adjacent retaining grooves.

6. The rotor drum in accordance with claim 1, wherein the blades of the first blade row are welded to the platform of the first blade row.

7. The rotor drum in accordance with claim 1, wherein the platform of the first blade row includes blade stubs on which are welded blade extensions, the height of the blade stubs being more than 10% of the radial height of the first blade row.

8. The rotor drum in accordance with claim 1, wherein the platform of the first blade row includes blade stubs on which are welded blade extensions, the height of the blade stubs being more than 25% of the radial height of the first blade row.

9. The rotor drum in accordance with claim 1, wherein the blades of the first blade row are at least partially cut into the body of the unmachined drum.

10. The rotor drum in accordance with claim 1, wherein the general curved profile of wall extends over most of the length of the drum and has a main concavity directed towards the main axis and extending over the major part of the length of the drum, the profile having a radius relative to the axis, which is at a maximum at the first blade row.

11. The rotor drum in accordance with claim 1, wherein the general curved profile of wall extends over most of the length of the drum or has a main concavity directed towards the main axis and extending over the major part of the length of the drum, the profile having a radius relative to the axis, which is at a maximum at the first blade row.

12. The rotor drum in accordance with claim 1, wherein the platform of the first blade row is raised relative to the wall directly upstream and downstream of the first blade row.

13. The rotor drum in accordance with claim 12, wherein the wall comprises:

two parts extending generally radially under the platform of the first blade row, so that the longitudinal section of the wall at the said platform has a π-shaped profile.

14. The rotor drum in accordance with claim 13, wherein the wall comprises:

at least one annular stiffener extending radially inwardly at the first blade row in the extension of at least one of the radial parts.

15. The rotor drum in accordance with claim 13, wherein the wall immediately upstream and downstream of the first blade row comprises:

a substantially constant thickness part which defines an annular space for accommodating a stator inner shell.

16. The rotor drum in accordance with claim 1, further comprising:

blades of the second blade row and the third blade row, each of the blades comprising:

a root housed in a retaining groove.

17. The rotor drum in accordance with claim 1, further comprising:

blades of the second blade row or the third blade row, each of the blades comprising

a root housed in a retaining groove.

18. The rotor drum in accordance with claim 1, wherein the retaining grooves are annular along the perimeter of the drum.

19. An axial turbomachine, comprising:

a rotor drum, comprising: a wall generally symmetrical in revolution about an axis thereof and having a generally curved profile, the wall being configured to support a plurality of blade rows; a first blade row formed by an annular platform integrally formed with the wall at a peak of the profile thereof in relation to the axis; and at least one second blade row directly downstream of the first blade row and a third blade row directly upstream of the first blade row, the second blade row being formed by one or more blade-retaining grooves formed on the wall;

wherein the rotor drum is a low-pressure compressor rotor having essentially three annular rows of rotor blades.