Stator assembly for turbomachine, and turbomachine

Abstract

The present document relates to a stator assembly (10) for a turbomachine, the stator assembly (10) comprising a first annular row of blades (10a), the blades (11a) of which are arranged to alternate circumferentially with blades (11b) of a second annular row of blades (10b), wherein the first annular row of blades (10a) and the second annular row of blades (10b) are movable circumferentially with respect to each other between a first configuration (P1), in which a leading edge of each blade (11b) of the second annular row of blades (10b) comes into contact with an intrados face of a circumferentially adjacent blade (11a) of the first annular row of blades (10a), and a second configuration (P2), in which each blade (11b) of the second annular row of blades (10b) is at a distance from said blade (11a) of the first annular row of blades (10a).

Description

Description Title: STATOR SET FOR TURBOMACHINE AND TURBOMACHINE technical field

[0001] This disclosure relates to a turbomachine stator assembly and to a turbomachine, such as an aircraft turbojet or turboprop, comprising such an assembly. Previous technique

[0002] Figure 1 schematically represents a known type of double-flow turbomachine 1 which comprises, from upstream AM to downstream AV according to the direction of gas flow within the turbomachine 1, a blower 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 an exhaust system at the rear body of the turbomachine 1.

[0003] The gas flow, including air, entering upstream of the turbomachine 1 first circulates through the blower 2 and then divides, on the one hand, into an annular circulation channel called the primary channel 8, and on the other hand, into an annular circulation channel called the secondary channel 9 surrounding the primary channel 8. The low pressure compressor 3, the high pressure compressor 4, the combustion chamber 5, the high pressure turbine 6 and the low pressure turbine 7 are located in the primary channel 8.

[0004] In this document, the terms "longitudinal", "radial" and "circumferential" are defined with respect to the longitudinal axis X of the turbomachine 1, the longitudinal axis X being coincident with the axis of rotation of the low pressure and high pressure rotors of the turbomachine 1. The terms "inside" and "outside", as well as "internal" and "external", are then defined according to the radial direction with respect to the longitudinal axis X.

[0005] Turbines and compressors generally comprise a stator and a rotor which is capable of pivoting relative to the stator around the longitudinal axis X of the turbomachine 1. The rotor comprises a plurality of annular rows of movable blades arranged longitudinally alternating with annular rows of stator blades, the radially external ends of the stator blades being fixed to a casing surrounding the annular rows of movable and stator blades.

[0006] It is well known that the geometry of the annular rows of stator blades is designed according to the operating conditions of the turbomachine. The higher the gas flow rate through the blade rows, the more advantageous it is to have an open inter-blade channel. This can be achieved, for example, by reducing the blade inclination relative to the longitudinal X-axis, or by increasing the inter-blade spacing, commonly referred to as the pitch. Conversely, the lower the flow rate, the more preferable it is to have a closed inter-blade channel, for example, by increasing the blade inclination relative to the longitudinal X-axis or by reducing the pitch. The geometry of the stator blades generally results from a compromise between these conditions. operation such that the chosen geometry is never perfectly suited to the flight condition at any given moment.

[0007] The invention aims to provide a simple, reliable and economical solution to this need. Summary

[0008] This document proposes a stator assembly for a turbomachine with a longitudinal axis. The stator assembly comprises a first annular row of blades arranged in alternating circumferential arrangement with blades from a second annular row. The blades of the first and second annular rows are, in particular, regularly distributed around the longitudinal axis.The first and second annular rows of blades are circumferentially movable relative to each other between a first configuration in which a leading edge of each blade of the second annular row of blades comes into contact with an intrados face of a circumferentially adjacent blade of the first annular row of blades, and a second configuration in which each blade of the second annular row of blades is at a distance from said blade of the first annular row of blades. The first and second configurations correspond in particular to two extreme configurations of the relative positioning of the first annular row of blades with respect to the second annular row of blades.

[0009] Each blade comprises an intrados face and an extrados face that meet at a leading edge and a trailing edge. Each blade also includes a chord line corresponding to the segment connecting the leading edge to the trailing edge of the blade profile, and a camber line corresponding to the mean camber line of the blade profile. Furthermore, the thickness of a blade is defined as a dimension of the blade perpendicular to the camber line in the plane of the blade profile.

[0010] In particular, a pair of blades is defined as formed by a blade from the first annular row of blades and a blade from the second annular row of blades circumferentially adjacent to the blade from the first annular row of blades on the side of the intrados face of the blade from the first annular row of blades.

[0011] Such a stator assembly, featuring two axially nested rows that can rotate relative to each other between two limiting configurations, offers the considerable advantage of allowing the stator assembly to be adapted to different operating conditions of the turbomachine. Consequently, this stator assembly makes it possible to optimize the efficiency and reduce the fuel consumption of the turbomachine.

[0012] The first configuration of the stator assembly, in which the two blades of each pair of blades—those of the first and second annular rows of blades, respectively—are in contact, is similar to a single annular row configuration with the same number of blades as either the first or second annular row. This first configuration allows the stator assembly to support a higher gas flow rate through it. Comparison of the second configuration. Indeed, the higher the flow rate, the lower, or even negative, the impact of the gas flow on the stator blades. Therefore, to limit aerodynamic losses, it is advantageous to have a more open inter-blade channel, for example, with a larger blade pitch. The term "pitch" refers to the circumferential spacing between successive blades. In the first configuration, the blade pitch is advantageously reduced compared to the second configuration because the two annular rows of blades are essentially a single row of blades. Consequently, the first configuration is better suited for higher flow rates.

[0013] Furthermore, positioning each blade of the second annular row of blades against the lower surface of a circumferentially adjacent blade of the first annular row of blades allows, on the one hand, for maintaining the upper surface of the first annular row of blades, which is the surface most aerodynamically active, and, on the other hand, for limiting aerodynamic losses at the transition between the two blades, for example, compared to an arrangement where the blade of the second annular row of blades would come against the upper surface of a circumferentially adjacent blade of the first annular row of blades. This is notably due to the camber and inclination of the lower surface of the blade of the first annular row of blades, which can "house" or "shelter" the circumferentially adjacent blade of the second annular row of blades.

[0014] The second stator assembly configuration, in which the blades of the two rows are spaced further apart, is similar to a configuration with twice the number of blades compared to the first or second annular row of blades. This second configuration allows the stator assembly to be better adapted to lower flow rates. Indeed, the lower the flow rate, the greater the impact of the gas flow on the stator blades. Therefore, to limit aerodynamic losses, particularly those due to stalling at the upper surface of the blades, it is advantageous to have a more closed inter-blade channel, for example, with a smaller blade pitch. This is made possible by doubling the number of blades in the second configuration.

[0015] Furthermore, it can be noted that the radial height of the blades in the first annular row of blades may differ from the radial height of the blades in the second annular row of blades. The leading edge of the blades in the second annular row of blades may only partially extend onto the intrados face of the blades in the first annular row of blades in the radial direction.

[0016] In particular, a first spacing is defined between consecutive blades of the first annular row of blades, specifically between the leading edges of consecutive blades of the first annular row of blades. In the second configuration, each blade of the second annular row of blades can be spaced from the circumferentially adjacent blade of the first annular row of blades by a second spacing, the second spacing preferably being less than 60% of the first spacing. In particular, the second spacing can correspond to a circumferential distance between the leading edge of the blade of the second annular row of blades and the camber line of the adjacent blade of the first annular row of blades. For example, the second spacing can be between 30% and 50% of the first spacing. In other words, the blades of the second annular row of blades can only move over a portion of the space between two corresponding consecutive blades of the first annular row of blades, the portion being delimited at one end by the intrados face of one of the two blades of the first annular row of blades.

[0017] Advantageously, the lower surface face of each blade in the first annular row of blades can include a geometric offset upstream, according to the direction of gas flow within the stator assembly, of the leading edge of the circumferentially adjacent blade in the second annular row of blades. This feature simplifies the design of the stator assembly so that the blade in the first annular row of blades accommodates the circumferentially adjacent blade in the second annular row of blades in the first configuration. More precisely, the geometric offset can correspond to a change in the curvature of said lower surface face.

[0018] The maximum thickness of each pair of blades in the first configuration can advantageously be less than or equal to the sum of the maximum thickness of the corresponding blade in the first annular row of blades and the maximum thickness of the circumferentially adjacent blade in the second annular row of blades. Such a configuration improves the aerodynamic performance of the stator assembly in the first configuration.

[0019] The ratio between the maximum thickness of each pair of blades in the first configuration and the maximum thickness of the corresponding blade in the first annular row of blades can advantageously be less than or equal to a coefficient between 1 and 1.2, for example, equal to 1. In other words, when the coefficient is strictly greater than 1, a slight "overhang" of the blade in the second annular row of blades would be permitted, meaning that it would not be entirely contained by the circumferentially adjacent blade in the first annular row of blades. Such a configuration improves the aerodynamic performance of the stator assembly in the first configuration.

[0020] The sum of the thickness of each blade in the first annular row of blades and the thickness of the circumferentially adjacent blade in the second annular row of blades, at a given longitudinal position of the blade, is preferably less than or equal to the maximum thickness of the blade in the first annular row of blades. Such a configuration reduces the maximum thickness of the blade pair in the first configuration. In this way, the blade pair offers a larger cross-sectional area compared to a conventional configuration with a single row of blades.

[0021] Advantageously, in the first configuration, the lower surface face of each blade in the second annular row of blades can form an aerodynamically continuous surface with a first surface of the lower surface face of the circumferentially adjacent blade in the first annular row of blades, the first surface being upstream of the leading edge of said blade. The second annular row of blades is oriented according to the direction of gas flow within the stator assembly. An aerodynamically continuous surface is defined as one where the gas flow against said surface is continuous, or, in other words, where the gas flow lines against said surface are continuous. In particular, the junction between the first surface and the lower surface face of the blade in the second annular row of blades is dimensioned so that, for given gas flow conditions, for example, in terms of velocity and angle of attack, the gas flow lines against said surface are continuous. The lower surface face of the blade pair can advantageously be free of any geometric step. Such a feature improves the aerodynamic profile of the stator assembly in the first configuration.

[0022] The upper surface of each blade in the second annular row of blades may advantageously have a shape complementary to a second surface of the lower surface of the circumferentially adjacent blade in the first annular row of blades, the second surface being downstream of the leading edge of said blade in the second annular row of blades, along the direction of gas flow within the stator assembly. In other words, the upper surface of the blades in the second annular row of blades at least partially matches the lower surface of the circumferentially adjacent blades in the first annular row of blades.The intrados face of each blade in the first annular row of blades can advantageously be formed from the first surface, delimited upstream by the leading edge of said blade and downstream by the geometric step, and from the second surface delimited upstream by the geometric step and downstream by the trailing edge of said blade.

[0023] Alternatively, a free volume can be provided between the upper surface of the second annular row of blades and the lower surface of the first annular row of blades in the first configuration. Such a free volume offers greater design flexibility from an aerodynamic and thermomechanical perspective, particularly regarding the lower surface and the trailing edge geometry of the first annular row of blades. The blades of the first annular row can thus advantageously have a more suitable geometry in the second configuration. Furthermore, such an arrangement also improves the vibrational behavior of the stator assembly.

[0024] In the first configuration, the upper surface of the blade in the second annular row of blades can advantageously come into contact with the trailing edge of each blade in the first annular row of blades adjacent to that blade in the second annular row of blades. This feature helps to limit losses due to gaps between the blades, particularly when there is a free volume between the respective blades of the first and second annular rows of blades.

[0025] Furthermore, the upper surface of the blades in the first annular row of blades can form an aerodynamically continuous surface with a portion of the upper surface of the blades in the second annular row of blades downstream of the trailing edge of the blades in the first annular row of blades. An aerodynamically continuous surface is defined as one where the gas flow against said surface is continuous, or, in other words, the gas flow lines against said surface are continuous. In particular, the junction between the upper surface of the blade of the first annular row of blades and the circumferentially adjacent portion of the upper surface of the blade of the second annular row of blades is dimensioned such that, for given gas flow conditions, for example in terms of velocity and angle of attack, the gas flow lines against said surface are continuous. The upper surface of the blade pair may advantageously be free of geometric step in the first configuration. Such a feature improves the aerodynamic profile of the stator assembly in the first configuration.

[0026] The leading edge of each blade in the second annular row of blades can advantageously be offset longitudinally from the leading edge of the circumferentially adjacent blade in the first annular row of blades by a distance of between 20% and 40%, preferably 30%, of the chord of said blade in the first annular row of blades. More precisely, the leading edge of each blade in the second annular row of blades is offset longitudinally downstream, in the direction of gas flow in the stator assembly, from the leading edge of the circumferentially adjacent blade in the first annular row of blades. Such an offset helps to reduce the maximum thickness of the blade pair in the first configuration.Indeed, this offset allows the maximum thicknesses of each blade profile to be shifted, so that the profile of the blade pair is thinner in the initial configuration than the sum of the maximum thicknesses of the two individual blade profiles. In this way, the blade pair offers a larger cross-sectional area compared to a conventional single-row blade configuration. Furthermore, the upstream flow, depending on the direction of gas flow within the stator assembly, then becomes advantageously influenced by the geometry of the blades in the first annular row. It is therefore easier to control the upstream flow by adjusting the geometry of the blades in the first annular row.

[0027] In particular, the leading edges of the blades in the first annular row of blades and the blades in the second annular row of blades can be aligned longitudinally. In other words, in this case, there is no longitudinal offset between the blades of the first annular row of blades and the blades of the second annular row of blades.

[0028] The trailing edge of each blade in the second annular row of blades can advantageously be offset longitudinally from the trailing edge of the circumferentially adjacent blade in the first annular row of blades by a distance of between 30% and 60% of the chord of said blade in the first annular row of blades. More precisely, the trailing edge of each blade in the second annular row of blades is offset longitudinally downstream, in the direction of gas flow in the stator assembly, from the trailing edge of the circumferentially adjacent blade in the first annular row of blades. Such an offset at the trailing edge makes control of the downstream flow according to the direction of gas flow within the stator assembly by adapting the geometry of the blades of the second annular row of blades.

[0029] The blades of the first annular row of blades and the second annular row of blades may advantageously have a chord of substantially the same length.

[0030] In the first configuration, the angle between the camber directions at the trailing edge of each blade in the first annular row of blades and the circumferentially adjacent blade in the second annular row of blades can advantageously be less than or equal to 5%. The camber direction at the trailing edge is defined as the tangent to the camber line at the trailing edge. This characteristic ensures that the exit angle remains virtually unchanged between the first and second configurations, despite the use of a stator assembly comprising two annular rows of blades.

[0031] Alternatively, in the first configuration, the angle between the camber directions at the trailing edge of each blade in the first annular row of blades and the circumferentially adjacent blade in the second annular row of blades can advantageously be greater than or equal to 5%. This characteristic provides flexibility in sizing the trailing angles of the blades in the first and second annular rows. Furthermore, this characteristic makes it possible to control an average trailing angle in the second configuration.

[0032] Preferably, the first annular row of blades can be fixed, and the second annular row of blades can be adapted to rotate relative to the first annular row of blades so as to be able to adjust the position of the blades of the second annular row of blades relative to the blades of the first annular row of blades.

[0033] Alternatively, the second annular row of blades can be fixed, and the first annular row of blades can be able to rotate relative to the second annular row of blades so as to be able to adjust the position of the blades of the first annular row of blades relative to the blades of the second annular row of blades.

[0034] The stator assembly may advantageously include a fixed radially internal annular ring and a fixed radially external annular ring, between which the blades of the first annular row of blades extend. More specifically, the radially external annular ring is fixed to a turbomachine housing. The stator assembly may also include at least one first ring from which the blades of the second annular row of blades extend radially inward. For example, said at least one first ring may comprise one or a plurality of first rings. The radially external annular ring notably includes a first annular groove, said at least one first ring being pivot-mounted in the first annular groove. This mounting configuration allows for easy adjustment of the position of the blades of the second annular row of blades relative to the blades of the first annular row of blades.

[0035] Said at least one first ring may extend longitudinally over the entire longitudinal length of the blades of the second annular row of blades, or alternatively may extend over a longitudinal length less than the longitudinal length of the blades of the second annular row of blades.

[0036] An internal radial end of the blades in the second annular row of blades may advantageously be free. The attachment of the blades in the second annular row of blades is thus ensured solely by said at least one first ring.

[0037] Alternatively, the stator assembly may include at least one second ring such that the blades of the second annular row of blades extend radially between said at least one first ring and said at least one second ring. For example, said at least one second ring may include one or a plurality of second rings. The first radially internal annular ferrule may include a second annular groove, said at least one second ring being pivot-mounted in the second annular groove.

[0038] Said at least one second ring may extend longitudinally over the entire longitudinal length of the blades of the second annular row of blades, or alternatively may extend over a longitudinal length less than the longitudinal length of the blades of the second annular row of blades.

[0039] According to another aspect, a compressor is described, for example a low pressure compressor or a high pressure compressor, comprising the stator assembly as previously described, in particular comprising a plurality of stator assemblies.

[0040] According to another aspect, a turbomachine, such as a turbojet or turboprop, is described, comprising the stator assembly as previously described.

[0041] Furthermore, the turbomachine may include a control unit that regulates the relative positioning between the first and second annular rows of blades, based on operational data from the turbomachine. The stator assembly can be controlled in the first configuration when the turbomachine requires a higher flow capacity or when minimizing aerodynamic losses is critical, for example, when the turbomachine is operating at high speed or steady state. The stator assembly can be controlled in the second configuration when the turbomachine is in a transitional state, for example, during acceleration. Brief description of the drawings

[0042] Other features, details and advantages will become apparent upon reading the detailed description below, and upon analyzing the attached drawings, in which:

[0043] [Fig. 1] illustrates respectively a schematic cross-sectional view of a turbomachine;

[0044] [Fig. 2] illustrates two partial schematic views of an example of a stator assembly according to this document respectively in a first configuration P1 (left figure) and in a second configuration P2 of the assembly (right figure);

[0045] [Fig. 3] illustrates two further partial schematic views of an example of a stator assembly according to this document respectively in a first configuration P1 (left figure) and in a second configuration of the assembly P2 (right figure);

[0046] [Fig. 4] schematically illustrates a partial cross-sectional view of an example of a stator assembly according to this document, this figure comprising a first enlargement A1 illustrated in the upper part named Figure 4A1 and a second enlargement A2 illustrated in the lower part named Figure 4A2;

[0047] [Fig. 5] schematically illustrates a partial cross-sectional view of another example of a stator assembly according to this document;

[0048] [Fig. 6], [Fig. 7], [Fig. 8], [Fig. 9], [Fig. 10] and [Fig. 11] schematically illustrate partial views of examples of stator assemblies according to this document. Description of the implementation methods

[0049] Reference is now made to Figures 2 and 3, which schematically represent two partial views of a stator assembly for a turbomachine with longitudinal axis X, as described in this document. Preferably, such a stator assembly is implemented in a compressor, in particular a high-pressure or low-pressure compressor, of a turbomachine as previously described with reference to Figure 1. This document also covers any type of turbomachine incorporating such a compressor, for example, a turboprop or turbojet engine for aircraft, preferably a turbofan engine.

[0050] The stator assembly 10 for turbomachine 1 comprises a first annular row of blades 10a whose blades are arranged alternately circumferentially with blades of a second annular row of blades 10b. The blades 11a, 11b of the first annular row of blades and the second annular row of blades are in particular regularly distributed around the longitudinal axis X.

[0051] Referring to Figure 4, each blade 11a, 11b comprises an intrados face 14a, 14b and an extrados face 15a, 15b which meet at a first end called the leading edge 12a, 12b and a second end called the trailing edge 13a, 13b. Each blade 11a, 11b also comprises a chord Ca, Cb, corresponding to the segment connecting the leading edge 12a, 12b to the trailing edge 13a, 13b of a blade profile, and a camber line 16a, 16b corresponding to the mean line of the blade profile. Furthermore, the thickness of a blade is defined as a dimension of the blade in a direction perpendicular to the blade camber line in the plane of the blade profile.

[0052] The first annular row of blades 10a and the second annular row of blades 10b are circumferentially movable relative to each other between a first configuration P1 and a second configuration P2. In the first configuration P1, the leading edge 12b of each blade 11b of the second annular row of blades 10b comes into contact with an intrados face 14a of a blade 11a circumferentially adjacent to the first annular row of blades 10a. In the second configuration P2, each blade 11b of the second annular row of blades 10b is at a distance from said blade 11a of the first annular row of blades 10a. The first and the The second configurations correspond in particular to two extreme configurations of relative positioning of the first annular row of blades with respect to the second annular row of blades.

[0053] In the following description, the blades 11a of the first annular row of blades 10a will be designated first blades 11a and the blades 11b of the second annular row of blades 10b will be designated second blades 11b. In particular, a pair of blades is defined, formed by a first blade 11a and a second blade 11b circumferentially adjacent to the first blade 11a on the side of the intrados face 14a of the first blade 11a. For the sake of simplification, only such a pair of blades will be described, the characteristics developed being applicable to all the sets of blades of the stator assembly.

[0054] Such a stator assembly, featuring two longitudinally nested rows that can rotate relative to each other between two limiting configurations, offers the considerable advantage of allowing the stator assembly to be adapted to different operating conditions of the turbomachine. Consequently, this stator assembly makes it possible to optimize the efficiency and reduce the fuel consumption of the turbomachine.

[0055] The first configuration of the stator assembly, in which the first and second blades 11a, 11b of each pair of blades are in contact, is similar to a single annular row of blades with the same number of blades as the first or second annular row of blades. This first configuration allows the stator assembly to withstand a higher gas flow rate compared to the second configuration. Indeed, the higher the flow rate, the lower, or even negative, the impact of the gas flow on the stator blades. It is therefore advantageous, in order to limit aerodynamic losses, to have a more open inter-blade channel, for example, with a larger blade pitch. The term "pitch" refers to the circumferential spacing between successive blades.In the first configuration, the spacing between the blades is advantageously reduced compared to the second configuration, because the two annular rows of blades are essentially a single row of blades. Consequently, the first configuration is better suited for higher flow rates.

[0056] Furthermore, positioning each second blade 11b on the side of the lower surface 14a of the first blade 11a allows, on the one hand, for maintaining the upper surface of the first annular row of blades, which is the surface most aerodynamically active, and, on the other hand, for limiting aerodynamic losses at the transition between the two blades, for example, compared to an arrangement where the second blade would be against the upper surface of the first blade. This is notably due to the camber and inclination of the lower surface of the first blade, which can "accommodate" or "shelter" the second blade.

[0057] The second configuration of the stator assembly, in which the blades of the two rows are spaced apart, is similar to a configuration with twice the number of blades compared to the first annular row of blades or the second annular row of blades. This second configuration allows the stator assembly to be better adapted at a lower flow rate. Indeed, the lower the flow rate, the greater the impact of the gas flow on the stator blades. Therefore, to limit aerodynamic losses, particularly those due to stalling at the upper surface of the blades, it is advantageous to have a more closed inter-blade channel, for example, with a smaller blade pitch. This is made possible by doubling the blades in the second configuration.

[0058] Furthermore, the turbomachine 1 may include a control unit that controls the relative positioning between the first annular row of blades and the second annular row of blades, notably based on the turbomachine's operating data. The stator assembly can be controlled in the first configuration when the turbomachine requires a higher flow capacity or when it is important to minimize aerodynamic losses, for example, when the turbomachine is at high speed or in steady state. The stator assembly can be controlled in the second configuration when the turbomachine is in a transitional state, for example, during acceleration.

[0059] Furthermore, it can be noted that the radial height of the first blades 11 a may be different from the radial height of the second blades 11 b. The leading edge of the second blades may only partially extend over the intrados face of the first blades in the radial direction.

[0060] In particular, a first spacing E1 is defined between the first consecutive blades 11a, specifically between the leading edges 12a of consecutive first blades 11a. In the second configuration P2, each second blade 11b can be spaced from the first blade 11a by a second spacing E2. In particular, the second spacing E2 can correspond to a circumferential distance between the leading edge 12b of the second blade 11b and the camber line 16a of the adjacent first blade 11a. The second spacing E2 is preferably less than 60% of the first spacing E1. For example, the second spacing E2 can be between 30% and 50% of the first spacing E1. In other words, the second blades can only move over a portion of the space between two corresponding consecutive first blades 11 a, the portion being delimited at one end by the intrados face 14a of one of the said two first blades 11 a.

[0061] The lower surface face 14a of the first blade 11a may include a geometric notch 142 upstream of the leading edge 12b of the second blade 11b, depending on the direction of gas flow within the stator assembly. This feature simplifies the design of the stator assembly so that the first blade 11a accommodates the second blade 11b in the first configuration. More precisely, the geometric notch 142 may correspond to a change in the curvature of the lower surface face 14a.

[0062] With reference to the upper part of Figure 4 (Figure 4A1) delimited by dotted lines, a maximum thickness w12max of each pair of blades in the first configuration can advantageously be less than or equal to the sum of a maximum thickness wl max of the first blade 11 a and a maximum thickness w2max of the second blade 11 b. Such a configuration makes it possible to improve the aerodynamic performance of the stator assembly in the first configuration P1.

[0063] The ratio between the maximum thickness w12max of each pair of blades in the first configuration and the maximum thickness wl max of the first blade 1 1 a can advantageously be less than or equal to a coefficient between 1 and 1.2, for example, equal to 1. In other words, when the coefficient is strictly greater than 1, a slight "overhang" of the second blade would be permitted, meaning it would not be entirely contained by the first blade. Such a configuration improves the aerodynamic performance of the stator assembly in the first configuration.

[0064] The sum of a thickness w1 of the first blade 11a and a thickness w2 of the second blade 11a, at the same given longitudinal position of the blade, is preferably less than a maximum thickness w1 max of the first blade 11a. Thickness is defined as the dimension along a direction perpendicular to the chord. Such a configuration reduces the maximum thickness of the blade pair in the first configuration. In this way, the blade pair offers a larger cross-sectional area compared to a conventional configuration with a single row of blades.

[0065] Advantageously, in the first configuration P1, the lower surface 14b of the second blade 11b can form an aerodynamically continuous surface with a first surface 140 of the lower surface 14a of the first blade 11a. This first surface 140 is located upstream of the leading edge 12b of the second blade 11b, according to the direction of gas flow within the stator assembly. An aerodynamically continuous surface is defined as one where the gas flow against said surface is continuous, or, in other words, where the gas flow lines against said surface are continuous. In particular, the junction between the first surface 140 and the intrados face 14b of the second blade 11b is dimensioned so that, for given gas flow conditions, for example in terms of speed and angle of attack, the gas flow lines against said surface are continuous, i.e. not showing any discontinuity at said junction.The lower surface of the blade pair can advantageously be free of geometric step. Such a feature improves the aerodynamic profile of the stator assembly in the first configuration P1.

[0066] A first plane is defined parallel to the chord Ca of the first blade 11a and passing through the lowest edge of the intrados face 14a of the first blade 11a in the circumferential direction from the extrados to the intrados. Then, at least one end of the intrados face 14b of the second blade 11b, including the leading edge 12b of the second blade 11b, is positioned between the first plane and the first surface 140 of the intrados face 14a of the first blade 11a.

[0067] The upper surface 15b of the second blade 11b may advantageously have a shape complementary to a second surface 141 of the lower surface 14a of the first blade 11a. This second surface 141 is located downstream of the leading edge 12b of the second blade 11b, according to the direction of gas flow within the stator assembly. In other words, the upper surface 15b of the second blades 11b at least partially matches the lower surface 14a of the first blades 11a. Specifically, the lower surface 14a of the first blade 11a may be formed of the first surface 140, delimited upstream by the leading edge 12a of the first blade 14a and downstream by the geometric step 142, and of the second surface 141 delimited upstream by the geometric step 142 and downstream by the trailing edge 13a of the first blade 11a.

[0068] Alternatively, with reference to Figure 5, a free volume 30 can be provided between the upper surface 15b of the second blade 11b and the lower surface 14a of the first blade 11a in the first configuration P1. Such a free volume 30 offers greater design flexibility from an aerodynamic and thermomechanical perspective, particularly regarding the lower surface 14a and the geometry at the trailing edge 13a of the first blade 11a. The first blades can thus advantageously exhibit a more suitable geometry in the second configuration. Furthermore, such an arrangement also improves the vibrational behavior of the stator assembly.

[0069] In the first configuration P1, the extrados face 15b of the second blade 11 b can advantageously come into contact with the trailing edge 13a of the first blade 11 a. Such a characteristic makes it possible to limit the losses due to the clearances between the blades, in particular in the case where there is a free volume between the first and second blades.

[0070] Furthermore, the upper surface 15a of the first blade 11a can form an aerodynamically continuous surface with a portion 150 of the upper surface 15b of the second blade 11b downstream of the trailing edge 13a of the first blade 11a. An aerodynamically continuous surface is understood to mean that the gas flow against said surface is continuous, or, in other words, that the gas flow lines against said surface are continuous. In particular, the junction between the upper surface 15a of the first blade 11a and said portion 150 of the upper surface 15b of the second blade 11b is dimensioned such that, for given gas flow conditions, for example in terms of velocity and angle of attack, the gas flow lines against said surface are continuous. The extrados face of the pair of blades may notably be devoid of geometric step in the first configuration P1.Such a feature makes it possible to improve the aerodynamic profile of the stator assembly in the first configuration.

[0071] The leading edge 12b of the second blade 11b can advantageously be offset longitudinally relative to the leading edge 12a of the first blade 11a by a first distance D1 of between 20% and 40%, preferably equal to 30%, of the chord Ca of the first blade 11a. In particular, the leading edge 12b of the second blade 11b is offset longitudinally downstream, according to the direction of gas flow in the stator assembly, relative to the leading edge 12a of the first blade 11a. Such an offset helps to reduce the maximum thickness of the blade pair in the first configuration. Indeed, this offset allows the positions of the maximum thicknesses of each blade profile to be shifted, so that the profile of the pair of blades is less thick in the first configuration than the sum of the maximum thicknesses of the profiles of the two respective blades.In this way, the pair of blades offers a larger cross-sectional area compared to a conventional single-row blade configuration. Furthermore, the upstream flow, depending on the direction of gas flow within the stator assembly, It then depends advantageously on the geometry of the blades in the first annular row of blades. It is then easier to control the upstream flow by adapting the geometry of the blades in the first annular row of blades.

[0072] In particular, the leading edges 12a, 12b of the first blade 11a and the second blade 11b can be aligned longitudinally. In other words, in this case, there is no longitudinal offset between the first and second blades.

[0073] The trailing edge 13b of the second blade 11b can advantageously be offset longitudinally relative to the trailing edge 13a of the first blade 11a by a second distance D2 between 30% and 60% of the chord Ca of the first blade 11a. In particular, the trailing edge 13b of the second blade 11b is offset longitudinally downstream, according to the direction of gas flow in the stator assembly, relative to the trailing edge 13a of the first blade 11a. Such an offset at the trailing edge makes it easier to control the downstream flow according to the direction of gas flow within the stator assembly by adapting the geometry of the second blades.

[0074] The blades of the first annular row of blades and the second annular row of blades may advantageously have a chord of substantially the same length.

[0075] With reference to the lower part of figure 4 (figure 4A2) delimited by dashed lines, an angle p is defined between the camber directions 17a, 17b at the trailing edge 13a, 13b respectively of the first blade 11a and the second blade 11b. The camber direction 17a, 17b at the trailing edge 13a, 13b is understood to be the tangent to the camber line 16a, 16b at the trailing edge 13a, 13b.

[0076] In the first configuration P1, the angle p can be less than or equal to 5%. This characteristic ensures that the output angle remains virtually unchanged between the first and second configurations despite the implementation of the stator assembly comprising two annular rows of blades.

[0077] Alternatively, in the first configuration P1, the angle p can advantageously be greater than or equal to 5%. This characteristic provides flexibility in sizing the trailing angles of the blades in the first and second annular rows. Furthermore, this characteristic makes it possible to control an average trailing angle in the second configuration.

[0078] Preferably, the first annular row of blades 10a can be fixed, and the second annular row of blades 10b can be adapted to rotate relative to the first annular row of blades so as to be able to adjust the position of the second blades 11b relative to the first blades 11a.

[0079] Alternatively, the second annular row of blades 10b can be fixed, and the first annular row of blades 10a can be adapted to rotate relative to the second annular row of blades 10b so as to be able to adjust the position of the first blades relative to the second blades.

[0080] In the following description, only the case where the first annular row of blades 10a is fixed, and the second annular row of blades 10b is able to rotate relative to the first annular row of blades will be described.

[0081] Figures 6 to 11 show partial cross-sectional views of various embodiments of the stator assembly. The stator assembly may advantageously comprise a fixed radially internal annular ring 21 and a radially external annular ring 20, between which the first blades 11a extend. More specifically, the radially external annular ring 20 is fixed to a turbomachine housing.

[0082] The stator assembly may also include at least one first ring 23 from which the second blades 11b extend radially inwards. The stator assembly may include only one first ring 23 (as shown in Figures 6, 7, 8, and 10), or a plurality of first rings, for example, two first rings 23 (as shown in Figures 9 and 11). It may be advantageous to use a plurality of first rings 23 when the second blades have a longitudinal length substantially equal to the longitudinal length of the first blades.

[0083] The radially external annular ferrule 20 includes, in particular, a first annular groove 22, said at least one first ring 23 being mounted in a pivot joint within the first annular groove 22, for example by means of pads. This mounting configuration allows easy adjustment of the position of the blades of the second annular row of blades relative to the blades of the first annular row of blades.

[0084] Said at least one first ring 23 may extend longitudinally over the entire longitudinal length of the second blades (as illustrated in Figures 8 and 10), or alternatively may extend over a longitudinal length less than the longitudinal length of the second blades (as shown in Figures 6 and 7).

[0085] Furthermore, as illustrated in Figures 6, 7, 8, and 9, a radially internal end 18b of the second blades 11b can advantageously be free. The attachment of the second blades 11b is thus ensured solely by said at least one first ring 23.

[0086] Alternatively, as illustrated in Figures 10 and 11, the stator assembly may include at least one second ring 25 such that the second blades 11b extend radially between said at least one second ring 25 and said at least one first ring 23. For example, said at least one second ring 25 may include one or two second rings 25. The radially internal annular ferrule 21 may include a second annular groove 24, said at least one second ring 25 being mounted in a pivot joint in the second annular groove 24.

[0087] Furthermore, said at least one second ring 25 may extend longitudinally over the entire longitudinal length of the second blades (as illustrated in Figures 10 and 11), or alternatively may extend over a longitudinal length less than the longitudinal length of the second blades (not shown in the figures).

Claims

Claims

1. Stator assembly (10) for a turbomachine (1) with a longitudinal axis (X), the stator assembly (10) comprising a first annular row of blades (10a) whose blades (11a) are arranged circumferentially alternating with blades (11b) of a second annular row of blades (10b), in which the first annular row of blades (10a) and the second annular row of blades (10b) are circumferentially movable relative to each other between a first configuration (P1) in which a leading edge (12b) of each blade (11b) of the second annular row of blades (10b) comes into contact with a pressure face (14a) of a circumferentially adjacent blade (11a) of the first annular row of blades (10a), and a second configuration (P2) in which each blade (11 b) of the second annular row of blades (10b) is spaced from said blade (11 a) of the first annular row of blades (10a).

2. Stator assembly (10) according to claim 1, in which the intrados face (14a) of each blade (11a) of the first annular row of blades (10a) comprises a geometric offset (142) upstream, in the direction of flow of the gases within the stator assembly (10), of the leading edge (12b) of the circumferentially adjacent blade (11b) of the second annular row of blades (10b).

3. A stator assembly (10) according to claim 1 or 2, wherein a maximum thickness (w12max) of each pair of blades in the first configuration (P1) is less than or equal to the sum of a maximum thickness (wl max) of the corresponding blade (11a) of the first annular row of blades (10a) and a maximum thickness (w2max) of the circumferentially adjacent blade (11b) of the second annular row of blades (10b).

4. Stator assembly (10) according to one of claims 1 to 3, in which a ratio between a maximum thickness (w12max) of each pair of blades in the first configuration (P1) and a maximum thickness (wl max) of the corresponding blade (11a) of the first annular row of blades (10a) is less than or equal to a coefficient between 1 and 1.

2.

5. Stator assembly (10) according to one of claims 1 to 4, wherein, in the first configuration (P1), a pressure face (14b) of each blade (11b) of the second annular row of blades (10b) forms an aerodynamically continuous surface with a first surface (140) of the pressure face (14a) of the circumferentially adjacent blade (11a) of the first annular row of blades (10a), the first surface (140) being upstream in the direction of flow of the gases within the stator assembly (10) of the leading edge (12b) of said blade (11b) of the second annular row of blades (10b).

6. Stator assembly (10) according to one of claims 1 to 5, in the first configuration (P1), a trailing edge (13a) of each blade (11a) of the first annular row of blades (10a) comes into contact with an extrados face (15b) of a circumferentially adjacent blade (11b) of the second annular row of blades (10b).

7. Stator assembly (10) according to claim 6, in which the extrados face (15b) of each blade (11b) of the second annular row of blades (10b) has a shape complementary to a second surface (141) of the intrados face (14a) of the circumferentially adjacent blade (11a) of the first annular row of blades (10a), the second surface (141) being downstream in the direction of flow of the gases within the stator assembly (10) of the leading edge (12b) of said blade (11b) of the second annular row of blades (10b).

8. Stator assembly (10) according to one of claims 1 to 7, in which the blades (11 a, 11 b) of the first annular row of blades (10a) and of the second annular row of blades (10b) have a chord (Ca, Cb) of substantially the same length.

9. Stator assembly (10) according to claim 8, wherein the leading edge (12b) of each blade (11b) of the second annular row of blades (10b) is offset longitudinally relative to a leading edge (12a) of the circumferentially adjacent blade (11a) of the first annular row of blades (10a) by a first distance (D1) of between 20% and 40% of the chord (Ca) of said blade (11a) of the first annular row of blades (10a).

10. Stator assembly (10) according to one of claims 7 or 8 combined with claim 6, in which a trailing edge (13b) of each blade (11b) of the second annular row of blades (10b) is offset longitudinally relative to the trailing edge (13a) of the circumferentially adjacent blade (11a) of the first annular row of blades (10a) by a second distance (D2) of between 30% and 60% of the chord (Ca) of said blade (11a) of the first annular row of blades (10a).

11. Stator assembly (10) according to claim 10, wherein, in the first configuration (P1), an angle (p) between camber directions (17a, 17b) at the trailing edge (13a, 13b) respectively of each blade (11a) of the first annular row of blades (10a) and of the circumferentially adjacent blade (11b) of the second annular row of blades (10b), is less than 5%.

12. Stator assembly (10) according to one of claims 1 to 11, comprising a radially inner annular shroud (21) and a radially outer annular shroud (20) being fixed, between which extend the blades (11 a) of the first annular row of blades (10a), the stator assembly (10) comprising at least one first ring (23) from which extend radially inwardly the blades (11 b) of the second annular row of blades (10b), said at least one first ring (23) being mounted in a pivot connection in a first annular groove (22) of the radially outer annular shroud (20).

13. Stator assembly (10) according to one of claims 1 to 12, in which a radially inner end (18b) of the blades (11b) of the second annular row of blades (10b) is free.

14. Turbomachine (1) comprising the stator assembly (10) according to one of claims 1 to 13.

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