Turbomachine and its method of use

Abstract

Turbomachine and its method of use. The present invention relates to a turbomachine comprising at least one rotor (100) and one stator (200). The rotor (100) is capable of rotating about a central axis (X) and includes at least one stator (200) and a first surface (150) disposed about the central axis (X). The stator (200) comprises a second surface (250) disposed opposite the first surface (150) about the central axis (X). One of said first and second surfaces (150, 250) has a groove inclined, with respect to a direction of rotation (R) of the rotor (100), in a first direction on a first side (A) of the groove and in a second direction opposite to the first direction on a second side (B) of the groove.During the operation of the turbomachine, the groove forms a fluid cushion with a thickness at least equal to a minimum distance (d2) between the first and second surfaces (150,250) to prevent fluid leakage between the first and second surfaces (150,250). Figure for the abstract: Fig. 1.

Description

Title of the invention: Turbomachine and its method of use technical field

[0001] This disclosure relates to the technical field of turbomachinery and more specifically to the sealing between the rotor and stator of a turbomachine. Prior art

[0002] Climate change is a major concern for many legislative and regulatory bodies worldwide. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by various states. In particular, an ambitious standard applies to both new types of aircraft and those already in operation, requiring the implementation of technological solutions to bring them into compliance with current regulations. Civil aviation has been actively working for several years now to contribute to the fight against climate change.

[0003] Technological research efforts have already led to very significant improvements in the environmental performance of aircraft. The Applicant takes into account the factors impacting all phases of design and development in order to obtain aeronautical components and products that are less energy-intensive, more environmentally friendly, and whose integration and use in civil aviation have moderate environmental consequences, with the aim of improving the energy efficiency of aircraft.

[0004] Consequently, the Applicant is constantly working to reduce its negative climate impact by using methods and operating virtuous development and manufacturing processes that minimize greenhouse gas emissions to the minimum possible in order to reduce the environmental footprint of its activity.

[0005] This sustained research and development work focuses on new generations of aircraft engines, the weight reduction of aircraft, in particular through the materials used and lighter on-board equipment, the development of the use of electrical technologies to provide propulsion, and, as essential complements to technological progress, aviation biofuels.

[0006] A turbomachine is generally understood to be a mechanism in which energy is transferred between at least one rotating part and a fluid. Such a rotating part of a turbomachine is called a rotor, and turbomachines also normally include at least one stationary part, called a stator. The energy transfer can take place from the rotor to the fluid. In this case, the turbomachine can be, for example A compressor, a blower, or a pump. Alternatively, energy transfer can occur from the fluid to the rotor. In this case, the turbomachine is a turbine. A turbomachine can also consist of several stages, and complex turbomachines are also possible, such as turbochargers, turbomotors, turboprops, or turbojets, comprising at least one generating stage in which energy is transferred from the rotor to the fluid and a receiving stage in which energy is transferred from the fluid to the engine. These complex turbomachines are notably used in aircraft propulsion.

[0007] Both rotors and stators typically have blades. Thus, it is common to alternate rotor blades and stator blades, commonly called distributors or rectifiers. In order to optimize energy transfer between the fluid and the rotor, this fluid should be channeled into a fluid channel passing through these blades. Furthermore, when the fluid is at a high temperature, as for example in gas turbines, leaks of hot fluid outside this channel could damage other components of the turbomachine. Consequently, it is necessary to prevent such leaks, particularly between the stator and the rotor.

[0008] For this purpose, thin sheets of metal are typically fixed under the base platform of the stator blades. In addition to such sheets, scrapers fixed to the rotor against abradable surfaces of the stator can also form seals between the rotor and the stator. However, these solutions have drawbacks. For example, the sheets can be complicated to produce, resulting in a high scrap rate. Furthermore, their attachment, typically by brazing, also complicates the production of the turbomachinery. As for the scrapers and the abradable surfaces, their contact causes wear, thus requiring regular maintenance. Description of the invention

[0009] A first aspect of this disclosure relates to a turbomachine comprising at least one rotor capable of rotating about a central axis and comprising a first surface disposed about the central axis, and at least one stator comprising a second surface disposed opposite to the first surface about the central axis, and in which at least one of said first and second surfaces has a groove inclined, with respect to a direction of rotation of the rotor, in a first direction on a first side of the groove and in a second direction opposite to the first direction on a second side of the groove.

[0010] Thanks to the grooving, the relative rotation of the first and second surfaces during the operation of the turbomachine can cause the formation of a fluid cushion, in a manner analogous to the hydrodynamic bearings disclosed by JH Vohr and CY Chow, in "Characteristics of Herringbone-Grooved, Gas-Lubricated Bearings," Journal of Basic Engineering, ASME, September 1965, pages 568-576, describes how these bearings prevent fluid from passing between the two surfaces. Leaks can thus be limited or even eliminated, increasing the efficiency of the turbine without subjecting its components to wear that might eventually require replacement. This makes it possible to increase performance while reducing environmental impact.

[0011] The rotor may, in particular, comprise a plurality of blades, each extending in a direction substantially perpendicular to the central axis, from a blade root to a blade tip. In this case, each blade may comprise a platform disposed at the blade root and / or the blade tip, with a spoiler to form the first surface, so as to facilitate the integration of this first surface into the rotor.

[0012] The grooving can notably be chevron-shaped, such as those disclosed in the aforementioned article by Vohr and Chow, as well as by E. Guenat and J. Schiffmann in "Dynamic force coefficients identification on air-lubricated herringbone-grooved journal bearing," Mechanical Systems and Signal Processing, Vol. 136, November 19, 2019, whose characteristics are well known and whose manufacture is comparatively simple. However, other alternative forms exist, such as diagonal grooving with grooves each having a constant inclination between its two ends, or spiral grooving with curved grooves.

[0013] In order to facilitate their production, but also to ensure the effective and stable generation of the fluid cushion, said first and second surfaces may, in particular, be substantially parallel to the central axis. By "substantially parallel," it is understood that they do not diverge from the direction of the central axis by an angle greater than the manufacturing tolerances, which may be, for example, ±1°. However, it is alternatively conceivable that said first and second surfaces may be inclined with respect to the central axis, or even perpendicular to it.

[0014] In order to ensure that the fluid cushion occupies substantially all the space between the first and second surfaces, so as to more effectively prevent fluid leakage between them, the first and second surfaces may be separated by a distance not exceeding 4 mm.

[0015] Furthermore, to ensure the generation of the fluid cushion, the grooving may have a depth of no less than 0.005 mm.

[0016] A second aspect of this disclosure relates to a method of using the turbomachine according to the first aspect, in which the first surface rotates with the rotor, around the central axis, at such a rotational speed relative to the stator with the second surface that the groove forms a fluid cushion of thickness at least equal to a minimum distance between the first and second surfaces, said cushion of fluid preventing fluid leakage between the first and second surfaces. Brief description of the drawings

[0017] The invention will be better understood and its advantages will become clearer upon reading the following detailed description of embodiments shown by way of non-limiting examples. The description refers to the accompanying drawings, which are schematic and intended primarily to illustrate the principles presented.

[0018] In these drawings, from one figure to another, identical or equivalent elements (or parts of elements) are identified by the same reference numerals. In these attached drawings:

[0019] [Fig-1] Fig. 1 is a schematic representation of a gas turbine engine following a first embodiment.

[0020] [Fig.2] The [Fig.2] represents a low-pressure turbine of the gas turbine engine of the [Fig.1],

[0021] [Fig.3] Fig.3 shows a detailed view of the low-pressure turbine of the [Fig.2],

[0022] [Fig.4] The [Fig.4] represents a rotor blade of the low-pressure turbine of the [Fig.2],

[0023] [Fig.5] The [Fig.5] represents a distributor of the stator of the low pressure turbine of the [Fig.2],

[0024] [Fig.6] Fig.6 represents a detailed view of a low-pressure turbine according to a second embodiment. Description of the implementation methods

[0025] Figure 1 schematically illustrates a gas turbine engine 1. In the direction of fluid flow, this gas turbine engine 1 may comprise a fan 2, a low-pressure compressor 3, a high-pressure compressor 4, a combustion chamber 5, a high-pressure turbine 6, a low-pressure turbine 7, and a nozzle 8. The assembly may be surrounded by a nacelle 9. The compressors 3, 4, the combustion chamber 5, and the turbines 6, 7 together form the gas generator 10, which is traversed by an air stream 17 and may itself be surrounded by a shroud 11 leading to the nozzle 8. Thus, an air stream 12 from the fan 2 may be defined between the shroud 11 of the gas generator 10 and an internal wall 13 of the nacelle 9.The high-pressure turbine 6 can be connected to the high-pressure compressor 4 by a first rotating shaft 14 for driving the latter, while the low-pressure turbine 7 can be connected to the blower 2 and the low-pressure compressor 3 by a second rotating shaft 15 coaxial to the first rotating shaft 14, in a similar manner.

[0026] The mass flow rate of the air stream 12 of the blower 2 can be substantially greater than that of the air stream 17 of the gas generator 10, and the ratio between these two mass flow rates is known as the bypass ratio. In the context of high and very high bypass ratio engines, where the diameter of the fan 2 can be particularly large in order to maximize its mass flow rate relative to that of the gas generator 10, a reduction gear 16 can be mechanically interposed between the second rotating shaft 15 and the fan 2, in order to reduce the rotational speed of the fan 2 and prevent the blade tips of the fan 2 from reaching excessive speeds.

[0027] Figure 2 illustrates in greater detail the low-pressure turbine 7 of the gas turbine engine 1. This low-pressure turbine 7 can be an axial turbine with a plurality of successive stages and comprising a rotor 100 and a stator 200. The rotor 100, which can be fixed to the second rotating shaft 15 and thus rotate with it around a central axis X of the gas turbine engine 1, can comprise, for each stage, a rotating blade 110 formed by a plurality of profiled blades 120 and extending each, in a radial direction Y substantially perpendicular to the central axis X, from a blade root 121 to a blade tip 122.

[0028] As illustrated in [Fig. 4], each blade 120 can be formed individually, although it is also possible to form a plurality of blades, or even an entire blade assembly, in a single piece. Each blade 120 may include, at the blade root 121, a fastening member 123, for example made of fir or a dovetail joint, for attaching the blade 120 to the rotor 100, as well as a platform 124 for defining the groove 17. Each blade 120 may also include, at the blade tip 122, another platform 125 for defining the groove 17, as well as, radially beyond this platform 125, blades 126 opposed to abradable elements 230 inside a housing 240 of the stator 200.

[0029] As illustrated in [Fig. 2], the stator 200 may include one or more fixed blades 210, called distributors or rectifiers, interposed between the rotating blades 110 of the rotor 100. [Fig. 5] illustrates an annular sector of such a fixed blade 210, comprising several profiled blades 220, each extending, in a direction substantially perpendicular to the central axis X, from a blade root 221 to a blade tip 222. This fixed blade 210 may also include internal ferrules 224 and external ferrules 225, respectively at the root and tip of the blade, which also contribute to defining the flow 17. Radially inside the internal ferrule 224, the fixed blade 210 may also have an abradable element 226 opposed to rotor blades 130 100.

[0030] In order to avoid a source of friction between rotor 100 and stator 200 during the operation of the gas turbine engine 1, and this over a wide temperature range, a certain axial clearance dl may be required between the platforms 124, 125 and the adjacent ferrules 224, 225. Some of the hot combustion gases circulating in the channel 17 can then escape through these gaps, as illustrated by the arrows F in [Fig. 3]. As in the illustrated embodiment, to prevent these leaks from progressing radially into the rotor 100, each blade 110 of the rotor 100 may have at least one surface 150 opposite a corresponding surface 250 of the stator 200, at a distance d2 which may be, for example, between 0 and 4 mm. The two surfaces 150 and 250 may be substantially cylindrical, coaxial, and parallel to the central axis X, although they may alternatively be conical, or even perpendicular to the central axis X.

[0031] The first surface 150, belonging to the rotor 100, may have a chevron pattern, comprising a plurality of grooves 300 inclined, with respect to a direction of rotation R of the rotor 100, in a first direction on a first side A of the groove and in a second direction opposite to the first direction on a second side B. These grooves 300 may have a depth d3 between 0.005 and 0.03 mm, a width d4 between 0.1 and 1 mm, and a pitch d5 between one and two times the width d4. Furthermore, the angle of inclination a of the grooves 300 with respect to a plane perpendicular to the direction of rotation R may be, for example, between 15° and 80°. It is, however, alternatively possible to form this groove on the second surface 250, belonging to the stator 200, rather than on the first surface 150 belonging to the rotor 100.Other forms of grooving are also conceivable as alternatives to chevron grooving, such as diagonal grooving with grooves each having a constant inclination between its two ends, or spiral grooving with curved grooves.

[0032] When the blade 110 of the rotor 100 is formed by individually formed blades 120, the first surface 150 can be formed by a set of spoilers 160 attached to the blades 120. In particular, as illustrated in [Fig.4], each spoiler 160 can be formed as an axial extension of the platform 124, offset in a radial direction inwards relative to it, so as to pass under the inner ferrule 224 of the adjacent fixed blade 210, which thus forms the second surface 250.

[0033] When the gas turbine engine 1 is in operation, the rotation and vibration of the first surface 150, with its grooves 300, relative to the second surface 250, generate a cushion of fluid in the space between the two surfaces 150 and 250, restricting the flow of fluid through this space. The two surfaces 150 and 250 thus form a virtual seal between them, preventing the leakage of hot combustion gases into the rotor 100.

[0034] Although in the first illustrated embodiment, the two opposing surfaces 150 and 250 are located radially inside the groove 17, in order to limit leakage towards the inside of the rotor 100, it is also possible to arrange them radially outside with respect to this groove 17, for example in place of the blade tips 126 and the abradable elements 230, as in embodiment a1 alternative illustrated in [Fig.6], in order to avoid leaks between stages of the turbomachine formed by the low pressure turbine 7.

[0035] Moreover, although in these two embodiments the rotor and stator to which the first and second surfaces respectively belong are those of a low-pressure turbine of a turbofan engine, it is also conceivable to apply this sealing solution to the high-pressure turbine, or to one of the compressors of this same gas turbine engine, or even to other types of turbomachinery.

[0036] Although the present invention has been described with reference to specific examples, it is evident that various modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. Therefore, the description and drawings should be considered in an illustrative rather than a restrictive sense.

Claims

Claims

1. Turbomachine comprising: at least one rotor (100) capable of rotating around a central axis (X) and comprising a first surface (150) arranged around the central axis (X), and at least one stator (200) comprising a second surface (250) arranged opposite the first surface (150) around the central axis (X), in which at least one of said first and second surfaces (150, 250) has an inclined groove, relative to a direction of rotation (R) of the rotor (100), in a first direction on a first side (A) of the groove and in a second direction opposite the first direction on a second side (B) of the groove.

2. Turbomachine according to claim 1, in which the rotor (100) comprises a plurality of blades (120) each extending, in direction (Y) substantially perpendicular to the central axis (X), from a blade root (121) to a blade head (122).

3. Turbomachine according to claim 2, in which each blade (120) comprises a platform (124, 125) arranged at the blade root and / or at the blade head, with a spoiler (160) to form the first surface (150).

4. A turbomachine according to any preceding claim, wherein the grooving is herringbone.

5. A turbomachine according to any preceding claim, wherein said first and second surfaces (150,250) are substantially parallel to the central axis (X).

6. A turbomachine according to any preceding claim, wherein the first and second surfaces (150,250) are separated by a distance (d2) not greater than 4 mm.

7. A turbomachine according to any preceding claim, wherein the grooving has a depth (d3) of not less than 0.005 mm.

8. Method of using the turbomachine according to any one of the preceding claims, in which the first surface (150) rotates with the rotor (100), around the central axis (X), at such a rotational speed relative to the stator with the second surface that the grooving forms a cushion of fluid of thickness at least equal to a minimum distance (d2) between the first and second surfaces (150, 250), said air cushion preventing fluid leakage between the first and second surfaces (150,250).