Stator assembly for a turbine engine, compressor, and turbine engine

Abstract

The invention relates to a stator assembly (10) for a turbine engine compressor, comprising two successive rows of upstream stator vanes (121) and downstream stator vanes (124) defining a tandem configuration, the vanes (121, 124) extending radially between inner and outer support members, wherein, within the tandem configuration, the chord (26) of the upstream vane (121), extending between the leading edge and the trailing edge of the vane, increases with the height of the upstream vane: at 0% of the height of the upstream vane (121), the chord (26) of the upstream vane is at least 1.9 times smaller than the chord of the upstream vane at 100% of the height of the upstream vane and, at 70% of the height of the upstream vane (121), the chord (26) of the upstream vane is at least 1.2 times smaller than the chord of the upstream vane at 100% of the height of the upstream vane.

Description

[0001] STATIC ASSEMBLY OF TURBOMACHINE, COMPRESSOR AND TURBOMACHINE

[0002] technical field

[0003] The present invention relates to a turbomachine stator assembly, a low-pressure compressor and a turbomachine.

[0004] Previous art

[0005] With a view to developing aircraft engines that significantly improve their environmental performance, reducing the size and weight of turbomachinery is crucial. To this end, it is possible to make turbomachine modules more compact, particularly compressors, especially low-pressure compressors, by reducing the number of compression stages. However, achieving the same compression ratio with fewer stages requires a higher rotor speed.

[0006] It is possible to consider speeds close to the speed of sound. The compressor is then said to be transonic when at least a radially external part of the rotor moves at a speed greater than that of sound.

[0007] Transonic compressors are characterized by a significant load on the rotor and stator blades because these must accelerate and straighten an airflow over a shorter axial distance. This load is even greater when the compressor includes variable-pitch blades, which, depending on the engine speed, impose a large deflection on the flow, and whose straightening therefore induces an even greater load.

[0008] Therefore, there is a need for stator blades that can withstand a wide range of incidence. In particular, there is a need for stator blades that can withstand high deflection over a wide range of incidence.

[0009] Description of the invention

[0010] To this end, the invention proposes a turbomachine compressor stator assembly comprising an internal support and an external support, two successive rows of stator blades defining a tandem configuration, the blades extending radially between the internal and external supports, the blades comprising a leading edge, a trailing edge, and a chord extending between the leading and trailing edges, the rows comprising an upstream annular row of blades and a downstream annular row of blades, located downstream of the upstream blades. One blade from the upstream annular row of blades and one blade from the downstream annular row of blades form a tandem.

[0011] Within the tandem, the stator assembly according to the invention may include one or more of the following characteristics taken individually or according to any possible technical combinations.

[0012] The upstream blade chord can be increasing with the upstream blade height, between the internal support and the external support.

[0013] At 0% height of the upstream blade between the inner support and the outer support, the chord of the upstream blade can be at least 1.9 times smaller than the chord of the upstream blade at 100% height of the upstream blade between the inner support and the outer support.

[0014] At 70% of the upstream blade height between the inner support and the outer support, the upstream blade chord can be at least 1.2 times smaller than the upstream blade chord at 100% of the upstream blade height between the inner support and the outer support.

[0015] According to one variant, within the tandem,

[0016] - at 30% of the upstream blade height between the internal and external supports, the upstream blade chord is at least 1.65 times smaller than the upstream blade chord at 100% of the upstream blade height between the internal and external supports, and / or

[0017] - at 50% of the upstream blade height between the internal support and the external support, the upstream blade chord is less than 1.35 times less than the upstream blade chord at 100% of the upstream blade height between the internal support and the external support.

[0018] According to one variant, within the tandem, - the ratio of the downstream blade chord to the upstream blade chord decreases with the height of the blades between the inner and outer supports, and / or

[0019] - at 0% blade height between the internal and external supports, the downstream blade chord is at least twice as large as the upstream blade chord, and / or

[0020] - at 20% of the blade height between the inner and outer supports, the chord of the downstream blade is at least 1.5 times greater than the chord of the upstream blade, and / or

[0021] - between 50% and 100% of the height of the blades between the internal support and the external support, the ratio of the chord of the upstream blade to the chord of the downstream blade is between 0.8 and 1.2.

[0022] According to one variant, within the tandem, the rope of the downstream dawn

[0023] - is decreasing between 0% height between the internal support and the external support and 40% height between the internal support and the external support, and / or

[0024] - is minimal, between 40% and 60% of the height between the internal support and the external support, and / or

[0025] - is increasing from 60% height between the internal support and the external support up to 100% height between the internal support and the external support.

[0026] According to one variant, within the tandem, from 0% height between the internal support and the external support up to 20% height between the internal support and the external support, the rope of the downstream blade is greater than the rope at 100% height between the internal support and the external support.

[0027] According to one variant, within the tandem, between 40% and 90% of height between the inner support and the outer support, the rope of the downstream blade is less than 95% of the rope of the downstream blade at 100% of height between the inner support and the outer support.

[0028] According to one variant, within the tandem, the blades also include

[0029] - an intrados and an extrados, - a line equidistant between the intrados and the extrados,

[0030] - a skeleton angle between the tangent to the equidistant line and the driving axis,

[0031] - a camber such as the difference between the skeleton angle at 95% of the chord from the leading edge and the skeleton angle at 5% of the chord from the leading edge, the camber ratio between the downstream blade and the upstream blade of a tandem is greater than 2 and less than 4 on at least one section along the height between the inner support and the outer support.

[0032] According to one variant, on at least one cross-section of the upstream blade of a tandem along the height between the inner support and the outer support, the angle between the tangent to the intrados and the chord has a minimum value between 5% of the leading edge and 95% of the chord, preferably the minimum value of the angle being positioned between 30 and 60% of the chord.

[0033] According to one variant, on at least one cross-section of the upstream blade of a tandem along the height between the inner support and the outer support, the evolution of the dimensionless skeleton angle

[0034] P95%”P5% with |3x%: the x% chord skeleton angle,

[0035] [35%: the skeletal angle at 5% chord, and

[0036] [395%: the skeleton angle at 95% of chord has a deviation of less than 10% over the interval from 20% of chord to 40% of chord from the leading edge.

[0037] According to one variant, the blades include a thickness between the intrados and extrados, the upstream blade has a thickness equivalent to at least 8% of the chord value reached at 15% of the chord from the leading edge, over at least one section along the height between the inner support and the outer support.

[0038] The invention also relates to a low-pressure aircraft turbomachine compressor comprising the assembly as described above.

[0039] The invention also relates to an aircraft turbomachine comprising the assembly as described above or a compressor as described above. According to one embodiment, the turbomachine comprises a variable-pitch propulsion unit driven by a speed reducer, the assembly being downstream of the propulsion unit.

[0040] According to one variant, the propulsion unit is unfaired.

[0041] The use, in this document, of the verb "comprendre" (to understand), its variants, and its conjugations, cannot in any way exclude the presence of elements other than those mentioned. The use, in this document, of the indefinite article "un" (a), "une" (an), or the definite article "le" (the), "la" (the), or "l'" (it) to introduce an element does not exclude the presence of multiple such elements.

[0042] The terms "first >>", "second >>", "third >>, etc. are used in this document exclusively to differentiate different elements, without implying any order between these elements.

[0043] All preferred embodiments and all advantages of the stator assembly according to the invention are applicable mutatis mutandis to the present compressor and turbomachine. The various embodiments may be considered individually or in combination.

[0044] Brief description of the figures

[0045] Other features and advantages of the present invention will become apparent upon reading the detailed description that follows, for understanding of which reference should be made to the accompanying figures which show:

[0046] - Figure 1, a schematic view of a turbomachine according to the invention;

[0047] - Figure 2, a schematic view of an example of a stator assembly comprising two rows of stator blades;

[0048] - Figure 3, a schematic view of the turbine blades of the turbomachine;

[0049] - Figure 4, a schematic view of an example of a stator assembly comprising two rows of stator blades;

[0050] - Figure 5, a graph of the evolution of dawn;

[0051] - Figure 6, a graph of the evolution of dawn;

[0052] - Figure 7, a graph of the evolution of dawn;

[0053] Figure 8 is a graph of the blade evolution. The drawings in the figures are not to scale. Similar features are generally denoted by similar reference numerals in the figures. For the purposes of this document, identical or analogous features may bear the same reference numerals. Furthermore, the presence of reference numerals or letters in the drawings shall not be considered limiting, even when such numerals or letters are specified in the claims.

[0054] Detailed description of embodiments of the invention

[0055] Reference points are shown in some of these figures as abstract geometric coordinate systems primarily to quantify and / or visualize properties of embodiments of the invention. In this document, reference is made to the directions "axial," "circumferential," and "radial," corresponding respectively to directions parallel to the drive axis X, essentially circular around the drive axis, and perpendicular to the drive axis. A reference point in Figure 1 specifically illustrates the direction of the referenced drive axis X and the radial direction Z, with a direction. The terms "inward" and "inward" naturally correspond to a direction toward the drive axis X along a radial direction, and the terms "outward" and "outward" to the opposite direction.The term "inlet / inlet" (and respectively "outlet / inlet"), when referring to the position of an element in an aircraft turbomachine or compressor, preferentially refers to a first (respectively, last) such element essentially upstream (respectively, essentially downstream) of the aircraft turbomachine or compressor.

[0056] Figure 1 illustrates a cross-section of an aircraft turbomachine 100 into which the assembly 10 according to the invention is to be integrated. This is an example of an architecture, as the invention applies to other turbomachine architectures. It may be an axial multiflow turbomachine comprising a number of elements. In succession, along the engine axis X, there is a propulsion unit 110, a fan 210, a low-pressure compressor 120, a high-pressure compressor 130, a combustion chamber 160, and then high-pressure and low-pressure turbines. These elements are known to a person skilled in the art. The propulsion unit 110 may be shrouded (by a shroud 112, in which case it is called a fan) or unshrouded (in which case it is called a propeller). The propulsion unit 110 can have variable timing, the timing being schematically represented by reference 109.In operation, the mechanical power of the low pressure and high pressure turbines is transmitted to the low pressure compressors 120 and high pressure compressors 130 respectively, as well as to the propulsion unit 110. A reducer 111 can be interposed, so that the rotational speeds of the propulsion unit 110 and the low pressure compressor 120 are proportional. The rotors of these compressors rotate around the motor axis X (indicating the direction of air intake and the direction of the thrust reaction), allowing them to draw in and compress air to bring it to suitable speeds, pressures, and temperatures, up to the inlet of the combustion chamber 160. From an airflow 200, the propulsion unit 110 generates a flow that splits into an airflow 201 and an airflow 202. The airflow 201 is primarily intended to generate a thrust reaction for the aircraft's flight.The airflow 202 in turn splits into an airflow 203 and an airflow 204, by a separating nozzle 70. The airflow 203 is mainly intended to generate an additional thrust reaction for the flight of the aircraft and the airflow 204 is mainly intended to pass axially through the aircraft turbomachine 100.

[0057] Although not systematically referenced in Figure 1, each compressor and turbine comprises one or more axial stages arranged in series. Each stage includes a stator (or rectifier) ​​with fixed blades and a rotor with movable blades that can be rotated around the drive shaft. Within a stage, the rotor draws in and accelerates an incoming airflow by deflecting it relative to the drive shaft axis X, and the following stator or rectifier straightens the flow along the drive shaft axis X and slows it down by converting part of its velocity into pressure. The fixed blades may have a fixed orientation and / or variable orientation (or pitch) (the blades occupying angular pitch positions). A variable pitch control system manages the angular pitch. These adjustable vanes are also known as variable pitch vanes, or by the English acronym "VSV" for "Variable Stator Vane".Their distinctive feature is that the inclination of their blades can vary relative to the X-axis of the motor (corresponding to the blade pitch), and particularly to the axes of the 120 and 130 compressors. The lower surfaces (intrados 16) and upper surfaces (extrados 18) of the blades can be more or less exposed to the airflow. The lower surfaces (intrados 16) extend to varying degrees in relation to the airflow in order to modulate the deflection, and therefore the straightening, imposed on the airflow. The compressors can have one or more stages of adjustable blades.

[0058] The low-pressure compressor 120, particularly of the transonic type, experiences a significant load on its rotor and stator blades because they must accelerate and straighten an airflow over a shorter axial distance. This load is even greater when the compressor includes variable-pitch blades, which, depending on the engine speed, impose a large deflection on the flow, and whose straightening therefore induces an even greater load. This is further accentuated with a variable-pitch propulsion unit 110. Thus, without limiting the scope of this design, the low-pressure compressor 120 comprises a stator assembly 10 consisting of tandem rows of blades. This consists of a succession of two rows or grids of stator blades, each of which partially contributes to straightening the flow. The two rows are placed successively and directly one after the other.Along the engine axis, from upstream to downstream, the blade rows are without any other blade rows and / or arms interposed axially between them. More specifically, the arrangement of two blade rows is such that the leading edge of the blades in both rows is without any other blade rows and / or arms interposed between them, particularly axially. This does not preclude the blades of successive rows from partially overlapping. The same applies to the blade arrangement within the tandem. Within the tandem, the two blades are close together. The rows are annular, around the engine's X-axis. A particularly critical point for flow straightening is the final compression stage of the compressor, which must deliver a substantially axial flow. Thus, to straighten the flow in such a compressor while limiting the aerodynamic load experienced by the final stage blades, assembly 10 comprises the blade rows in tandem, for example, in the final stage.Thus, a first array of blades, designed to accommodate a flow with a significant variation in the angle of attack, is followed by a second array of blades responsible for completing the remaining deflection. This second array maintains its optimal performance thanks to the filtering action of the first array. Each blade in the tandem configuration has specific profile characteristics (depending on a streamline and the stacking of profiles along the blade height) to withstand a high load and a large deflection over a wide angle of attack range. With this assembly, it is possible to design a tandem stator or rectifier capable of tolerating a wide range of flow angles (for example, an angle of attack of 20°, possibly with positive and negative angles) and achieving a large flow deflection (up to 60°).In addition, the optimization proposed by set 10 allows for better performance in terms of aerodynamic losses, residual gyration at the outlet and pumping margin.

[0059] An example of a stator assembly 10 is described below with reference to Figures 2 to 4. The stator assembly 10 thus has a tandem configuration with two rows or grids of stator blades 121, 124 forming a double grid. Figures 3 and 4 are cross-sections along AA' of Figure 2. The stator assembly 10 comprises two successive rows of stator blades. In the stator assembly 10, an upstream blade 121 of the upstream annular row of blades 121 and a downstream blade 124 of the downstream annular row of blades 124 form a tandem (the tandem therefore comprising two blades, one blade in each row). The stator assembly 10 comprises a plurality of tandems. Within each tandem, there is an upstream blade 121 of the annular row of upstream blades 121 and a downstream blade 124 of the annular row of downstream blades 124.The characteristics, technical effects and advantages indicated for a tandem of the stator assembly 10 apply to all tandems formed of a blade in each row.

[0060] The stator assembly 10 comprises an upstream row of blades 121 and a downstream row of blades 124. The blades extend from a radially internal support 52 to a radially external support 54, as shown in Figure 2. The internal support 52 and external support 54 may be mounting platforms for attachment to a supporting structure. The internal support 52 and external support 54 may also be ferrules describing 360° around the X-axis or angular sectors of ferrules describing an angle of a few degrees or a few tens of degrees around the X-axis. The internal support 52 and the external support 54 define an airflow channel 12, particularly for channeling an airflow such as the flow 204. The upstream blades 121 and downstream blades 124 may be supported by a common internal support 52 and a common external support 54. Blades 121, 124 can be fixed.The blades 121 and 124 can have a fixed position relative to the internal support 52 that supports them, or a variable position relative to the internal support 52 that supports them. The blades 121 and 124 extend radially between the two supports. The blades 121 and 124 extend along a radial Z direction of the compressor, transverse to the motor axis X. The blades 121 and 124 can also extend along another direction, inclined relative to the X and Z directions.

[0061] Between the internal support 52 and external support 54, the assembly 10 is distinguished by the profile of the blades 121, 124 according to at least one cross-section along the height H121, H124 of the blades and by the stacking of the profiles along the height of the blades. The blades 121, 124 comprise an intrados 16 and an extrados 18. The blades 121, 124 comprise an equidistant line 20 between the intrados 16 and the extrados 18. The blades 121, 124 also comprise a leading edge 22 upstream in the airflow and a trailing edge 24 downstream in the airflow. The blades 121, 124 also include a chord 26 extending between the leading edge 22 and the trailing edge 24. A tangent 28 to the equidistant line 20 is shown.

[0062] The angle of attack (or angle of incidence) is the angle formed by the direction of the airflow at the leading edge 22 with respect to the tangent 28 to the equidistant line 20. It is the angle between one or the other of the arrows 30 representing the direction of the airflow and the tangent 28 to the equidistant line 20 (the tandem blades being capable of righting the airflow, which can be on either side of the tangent 28, i.e., with a positive or negative angle of attack). The arrows 30 show different (maximum) angles of attack. The distance between the two arrows 30 corresponds to the range of angles of attack.

[0063] The evolution, along the chord 26, of the skeleton angle 29 between the tangent 28 to the equidistant line 20 and the motor axis X is called the skeleton angle law. We position ourselves at X% of the chord to position the skeleton angle law.

[0064] The thickness law describes the evolution, along chord 26, of the thickness 50 of the blade between the intrados 16 and the extrados 18. The thickness 50 is measured perpendicular to the skeleton line 20.

[0065] The blade pair 121, 124 is capable of providing a large air deflection for operation over a wide range of air incidence angles on the upstream blade 121, for example, a range of 20° between the two sweeps 30 (the distribution of the range on either side of the tangent 28 can be variable, for example [-10°; +10°] or [-5°; +15°], etc.). The blade pair 121, 124 is also capable of straightening the airflow at the trailing edge of the downstream blade 124 so that the straightened airflow is as close as possible to the drive axis X – particularly when the pair is the final stage of the compressor. Thus, the blade pair 121, 124 is capable of providing a large airflow deflection. In Figure 3, the straightened airflow is represented schematically by arrow 25 (of the downstream blade 124). The total deflection of the air by the blade pair is the angle between arrow 25 (of the downstream blade 124) and arrow 30 (of the upstream blade 121).The blade pair 121, 124 is capable of providing a large deflection (greater than 40° to 50°, even up to 60°). Thus, the pair supports a large skeleton angle 29 for the upstream blade and a significant variation in incidence (corresponding to the variation of the deflection 30 with respect to the tangent 28).

[0066] The blades 121, 124 each have a certain camber defined as the difference between the skeleton angle 29 at 95% of the chord 26 from the leading edge 22 and the skeleton angle 29 at 5% of the chord 26 from the leading edge 22. The skeleton angle 29 at X% of the chord 26 from the leading edge 22 means the angle 29 (between the tangent 28 to the equidistant line 20 and the driving axis X) taken at a position at the intersection between a perpendicular to the chord 26 and the equidistant line 20, the perpendicular being at a distance 27 from the leading edge 22 corresponding to X% of the length of the chord 26 from the leading edge 22 (approximately 25% in Figure 3). The camber of the blades 121, 124 allows for a straightening of the airflow. The camber of each blade 121, 124 is determined to avoid reaching flow boundary conditions, conditions in which the airflow separates from the blades under the effect of the adverse static pressure gradient.In the event of boundary layer separation, the acceleration and / or straightening of the flow is no longer guaranteed, which impairs compressor efficiency. There is therefore a link between deflection (air angle in operation) and camber (geometric angle of the blade).

[0067] The camber ratio between the downstream blade 124 and the upstream blade 121 of a tandem turbine is greater than 2 and less than 4 over at least one section along the height between the inner and outer supports (at the same height for both blades). Such a camber ratio is over at least one section between 5% and 95% of the height, preferably over sections at 5% and 95% of the height, preferably over sections at 5%, 30%, 70% and 95% of the height, preferably over sections at 5%, 30%, 50%, 70% and 95% of the height, preferably over the entire height of both blades of the same tandem between 5% and 95%, or even preferably over the entire height of both blades of the same tandem. In this way, the shape of the profile of the upstream (front) blade 121 of the tandem is made so as to maintain a high incidence and to deviate little in comparison to the shape of the profile of the downstream (rear) blade 124 of the tandem, which is made so as to deviate strongly.The downstream blade 124 has a camber two to four times greater than the camber of the upstream blade 121 (within a tandem – and therefore within all tandems consisting of one blade in each annular row), which allows the downstream blade to deflect the airflow more effectively. Thus, the first upstream stator blade array 121 is designed with moderate deflection to accommodate the flow upstream of the assembly 10 over a wide range of angles of attack and to provide the second downstream stator blade array 124 with a substantially uniform supply at every operating point of the turbomachine 100. The second stator blade array 124 operates at a near-single angle of attack and completes the deflection without having to manage variations in angle of attack. This allows for stator blades that can withstand a large deflection over a wide range of incidence.In absolute terms, the camber of each upstream blade 121 is between 10° and 25°, preferably between 12° and 22°. Assembly 10 prevents a single blade from having to withstand an excessively large difference in angle of incidence between two extreme operating points of the turbomachine, which would be associated with a significant deflection. According to the tandem configuration of assembly 10, the upstream blade 121 supports the airflow angle of incidence over a wide range, and the downstream blade 124 ensures the airflow deflection over a wide range. This tandem configuration meets the need for blades that are more tolerant and more resistant to angle of incidence and aerodynamic deflections with respect to flow separation on the blade face. This is particularly important within the technical context described.

[0068] The evolution of the angle between a tangent to the lower surface 16 and the chord 26 is called the intrados angle law. Within a tandem wing, the upstream blade 121 can be such that the angle between the tangent to the lower surface 16 and the chord 26 has a minimum value between 5% of the leading edge 22 and 95% of the chord 26 (i.e., 5% of the trailing edge 24) over at least one section along the height between the inner and outer supports. Thus, the upstream blades 121 have an intrados curvature along the chord that limits air separation, even when the air incidence range is large. Preferably, the minimum value of the angle between the tangent to the lower surface 16 and the chord 26 is positioned between 30% and 60% of the chord. This allows the airflow to be diverted, while allowing the blades to withstand a heavy load over a wide range of angles of attack.

[0069] For the leading edge blade 121 of a tandem wing, the difference between the minimum angle between the tangent to the lower surface and the chord 26 and the lower surface angle (between the tangent to the lower surface and the chord 26) at 5% of the leading edge can be at least three times greater than the difference between the lower surface angle at 95% of the chord and the lower surface angle at 5% of the leading edge, over at least one cross-section along the height between the inner and outer supports. Thus, the leading edges of the blades 121 have a lower surface close to the leading edge 22, which allows, in particular, for proper airflow guidance along the lower surface to limit air separation, even when the airflow angle of attack is wide.

[0070] On at least one section along the height between the internal support and the external support, the evolution of the dimensionless skeleton angle of the upstream blade 121 defined by the formula ^ %0 / °~^ 5%(with |3x%: the skeleton angle 29 at x% of the chord, x being within the interval [20%, 40%], [35%: the skeleton angle 29 at 5% of the chord, and [395%: the skeleton angle 29 at 95% of the chord) may exhibit a deviation of less than 10% over the interval from 20% of the chord to 40% of the chord (from the leading edge 22). For example, is less than 10% (but also for all values ​​of x within the above range. This ensures good stability of the upstream blade's angle of attack while allowing for some deflection, the downstream blade providing the necessary deflection expected from the tandem. Within a tandem, the skeleton angle 29 of the upstream blade at 5% of its chord is greater than 50°. This ensures stability with respect to angles of attack that can vary significantly, and even be negative.

[0071] The blades 121 and 124 have a thickness of 50 between the lower surface 16 and the upper surface 18. The leading edge blade 121 of a tandem wing can have an equivalent thickness of between 8% and 25%, preferably 8% to 15%, of the chord length (i.e., at least 8% of the chord length from the leading edge) reached at 15% of the chord length from the leading edge (over at least one section along the height between the inner and outer supports). This allows the leading edge blades 121 to have a high tolerance and high resistance to high angles of attack and their variations.

[0072] The absolute skeleton deflection is defined as the absolute value of the difference between the skeleton angle 29 at 95% of chord 26 and the skeleton angle 29 at 5% of chord 26. Within a tandem, over at least one section along the height between the inner and outer supports, the absolute skeleton deflection of the downstream blade 124 can exceed 35°. This allows the downstream blade 124 to withstand a high load on a high deflection while maintaining optimal operation thanks to the filtering action of the upstream blade 121. Figure 4 is a schematic view of an example of a stator assembly with two rows of stator blades, with only two blades 121 and 124 shown per row (corresponding to a tandem). The axial gap 60 formed along the X axis between the two rows of upstream blades 121 and downstream blades 124 can be likened to a gap along the X axis between the trailing edge 24 of the upstream blade 121 and the leading edge 22 of the downstream blade 124 of a tandem.In the example shown in the figures, the blade rows 121 and 124 do not overlap, but they could. With (XBA, YBA) the coordinates of the leading edge 22 of the downstream blade 124 and (XBF, YBF) the coordinates of the trailing edge 24 of the upstream blade 121, the axial gap 60 can be written as AX = XBA - XBF. The azimuthal gap 62 (or circumferential spacing, or spacing in the circumferential direction transverse to the driving axis X) formed along the Y-axis between the two blade rows upstream 121 and downstream 124 can be likened to a gap along the Y-axis between the trailing edge 24 of the upstream blade 121 and the leading edge 22 of the downstream blade 124 of a tandem turbine. The azimuthal deviation 62 can be noted as AY = YBF - YBA.

[0073] Regarding the relative positioning of each blade in the tandem assembly, the azimuthal gap 62 between the trailing edge 24 of the upstream blade 121 and the leading edge 22 of the downstream blade 124 can be between 3 mm and 8 mm, over at least one cross-section along the height between the inner and outer supports. This ensures a circumferential spacing that is sufficiently small to maintain flow continuity while being large enough to limit or prevent any aerodynamic blockage, particularly pumping. The axial gap 60 between the leading edge 22 of the downstream blade 124 and the trailing edge 24 of the upstream blade 121 can be between 0.5 mm and 3 mm, over at least one cross-section along the height between the inner and outer supports. This ensures that there is an axial spacing length that allows for continuous flow and that the downstream blade 124 operates in a quasi-single incidence.

[0074] The stator assembly's ability to withstand deflection and angle of attack is achieved through the thickness and / or angle laws of the upstream and downstream blades of the tandem, and / or through the relative positioning of the blades. Over at least one cross-section along the height between the inner and outer supports, the shape of the upstream blade's profile provides greater robustness and better resistance to angle of attack variations, while the shape of the downstream blade's profile allows for the majority of the deflection to be achieved.

[0075] The assembly's ability to withstand deflection and angle of attack stresses is achieved through the thickness and / or angle laws of the upstream and downstream blades of the tandem, and / or through the relative positioning of the blades. Over at least one cross-section along the height between the inner and outer supports, the shape of the upstream blade's profile provides greater robustness and better resistance to variations in angle of attack, while the shape of the downstream blade's profile allows for the majority of the deflection. Furthermore, given the significant behavioral differences in airflow between the root and tip of the blades in assembly 10, a specific evolution of the chord and profile shape of the upstream and downstream blades within the tandem assembly, as a function of the blade height (or in other words, according to the stacking of profiles of different heights), gives the assembly the ability to withstand deflection and angle of attack stresses.

[0076] More specifically, within the tandem, the paddle rope has one of the following characteristics, alone or in combination.

[0077] The invention relates in particular to a tandem assembly with an upstream blade whose chord 26 can increase with the height of the upstream blade 121 between the internal support 52 and the external support 54. This allows for a blade profile that adapts to the differential behavior of the airflow, giving the assembly the capacity to withstand deflection and angle of attack constraints. At 0% height of the upstream blade 121 between the internal support 52 and the external support 54, the chord 26 of the upstream blade 121 can be at least 1.9 times smaller than the chord 26 of the upstream blade 121 at 100% height of the upstream blade 121 between the internal support 52 and the external support 54. This allows it to withstand high angles of attack even when the flow is less turbulent.At 70% of the height of the upstream blade 121 between the inner support 52 and the outer support 54, the chord 26 of the upstream blade 121 can be at least 1.2 times smaller than the chord 26 of the upstream blade 121 at 100% of the height of the upstream blade 121 between the inner support 52 and the outer support 54. This results in a blade profile capable of withstanding high angles of attack and high air velocities. The stator assembly therefore has stator blades that can withstand a wide range of angles of attack – this being ensured by the upstream blade. The stator assembly, through a tandem structure, therefore presents stator blades which maintain a strong deflection (by the downstream blade of the tandem, the upstream blade offering an almost unique incidence (over a large range) to the downstream blade) over a large range of incidence (by the upstream blade of the tandem).

[0078] At 30% of the height of the upstream blade 121 between the internal support 52 and the external support 54, the chord 26 of the upstream blade 121 can be at least 1.65 times smaller than the chord 26 of the upstream blade 121 at 100% of the height of the upstream blade 121 between the internal support 52 and the external support 54. This allows high angles of attack to be maintained even as the flow becomes progressively more turbulent. At 50% of the height of the upstream blade 121 between the internal support 52 and the external support 54, the chord 26 of the upstream blade 121 can be at least 1.35 times smaller than the chord 26 of the upstream blade 121 at 100% of the height of the upstream blade 121 between the internal support 52 and the external support 54. At mid-height of the blade, this makes it possible to give a balance between the ability to maintain a high angle of attack while arranging the airflow in such a way as to be strongly deflected by the downstream blade 124.This enhances the ability of the stator assembly to present stator blades that hold a large range of incidence and to present, by a tandem structure, therefore presents stator blades that hold a large deflection (by the downstream blade of the tandem, the upstream blade offering an almost unique incidence (over a large range) to the downstream blade) over a large range of incidence (by the upstream blade of the tandem).

[0079] Advantageously, at 100% height of the upstream blade 121 between the internal support 52 and the external support 54, the chord 26 of the upstream blade 121 can be between 20mm and 50mm, preferably between 25mm and 45mm, even more preferably between 30mm and 35mm.

[0080] Figure 5 shows the chord length C (in mm) of the upstream blade 121 (curve 40) and the downstream blade 124 (curve 41) on the x-axis and the percentage height H of the blade on the y-axis. Curve 40 shows the growth of the chord of the upstream blade 121 from the root (0% height) to the tip (100% height). According to Figure 5, the chord of the upstream blade 121 is preferably strictly increasing. Figure 6 shows the ratio R of the chord of the upstream blade at 100% height to the chord of the upstream blade at the current height on the x-axis and the height H of the blade on the y-axis.

[0081] Within the tandem, the ratio of the chord 26 of the downstream blade 124 to the chord 26 of the upstream blade 121 can decrease with the height of the blades between the inner support 52 and the outer support 54. This allows the air deflection to be adapted according to the height of the tandem blades and transfers the deflection load largely to the downstream blade. At 0% blade height between the inner and outer supports, the chord 26 of the downstream blade 124 can be at least twice as long as the chord 26 of the upstream blade 121. This provides the necessary length for deflection and also better manages the aerodynamics related to the proximity to the support. At 20% height of the blades between the internal support and the external support, the chord 26 of the downstream blade 124 can be at least 1.5 times larger than the chord 26 of the upstream blade 121. This allows a balance between deflection and holding of the blades.Between 50% and 100% of the blade height between the inner and outer supports, the ratio of the chord 26 of the upstream blade 121 to the chord 26 of the downstream blade 124 can be between 0.8 and 1.2. This favors air deflection by the downstream blade 124. Figure 8 shows the evolution of the ratio R of the chord of the downstream blade 124 to the chord of the upstream blade 121 on the x-axis and the blade height H on the y-axis. The chord of the downstream blade 124 is greater than the chord of the upstream blade 121 over approximately 85% of the blade height, which shows that the flow deflection occurs primarily by the downstream blade 124.

[0082] Within the tandem, the chord 26 of the downstream blade 124 can decrease from 0% height between the inner support 52 and the outer support 54 to 40% height between the inner support 52 and the outer support 54. This allows for a strong deflection when the airflow is less turbulent. The chord 26 of the downstream blade 124 can be minimal between 40% and 60% height between the inner and outer supports. This allows for a balanced deflection when the flow behavior differential at mid-height is strong compared to the blade root and tip. The chord 26 of the downstream blade 124 can increase from 60% height between the inner support 52 and the outer support 54 to 100% height between the inner support 52 and the outer support 54. This allows for a strong deflection at high flow velocities.In Figure 5, curve 41 shows the decrease in the chord of the downstream blade 124 from the foot (0% height) to 40% height, and then the increase in the chord of the downstream blade 124 from 60% height to 100% height. Between 40% and 60%, and preferably between 50% and 60%, the chord of the downstream blade 124 is minimal. At the foot, the chord of the downstream blade 124 can be greater than at the tip, particularly between 15% and 35% greater.

[0083] Within the tandem, from 0% height difference between the inner and outer supports up to 20% height difference between inner support 52 and outer support 54, the rope 26 of the downstream blade 124 can be greater than the rope of the downstream blade at 100% height difference between inner support 52 and outer support 54. This allows for the placement of only a significant rope in areas of high demand. Figure 7 shows the ratio R of a rope of the downstream blade 124 at the current height relative to the rope of the downstream blade 124 at 100% height on the x-axis and the height H of the blade on the y-axis. Curve 43 shows that from the bottom (0% height) up to 20% height difference, the rope of the downstream blade 124 is greater than the rope at the top at 100% height difference. Curves 41 and 43 show that the chord length is not the same at the bottom of the downstream blade as at the top of the downstream blade, which allows adaptation to variations in airflow speed along the height of the downstream blade.

[0084] Within the tandem, between 40% and 90% of the height between the inner support 52 and the outer support 54, the chord 26 of the downstream blade 124 can be less than 95% of the chord of the downstream blade 124 at 100% of the height between the inner support 52 and the outer support 54. This allows adaptation to the strong speed differential that exists at the head of the downstream blade, in order to ensure the appropriate deflection.

[0085] Thus, the stator assembly consisting of two closely spaced (tandem) blades, with an upstream and a downstream blade, defined by their thickness and angle profiles, along with the coupling of their relative positioning and stacking, allows for a large deflection over a wide range of angles of attack. This solution enables the achievement of significant deflections across a broad range of angles of attack under varying flow conditions along the vertical axis.

[0086] The invention also relates to an (axial) compressor for a turbomachine, comprising the stator assembly 10, and also to an aircraft turbomachine with the compressor and the assembly 10. This can be any type of aeronautical turbomachine, and in particular aircraft turbomachines such as turbojets and turboprops. It can be a turbomachine comprising the propulsion unit 110 upstream (or inlet) of the turbomachine. The propulsion unit 110 can be of the variable-pitch type or of the variable-pitch type driven by the reduction gear 111. The propulsion unit 110 can be of the ducted (fan) type, or of the unducted type (propeller and also a pair of unducted co-rotating or counter-rotating propellers). This latter type is also called "open-fan" or "open-fan." It could be the 120 low pressure compressor.The compressor can be a transonic variable-geometry compressor, in which the stator vanes have variable pitch. The compressor (and assembly 10) can be located downstream of the propulsion unit 110 (downstream meaning after the propulsion unit, separated from it by other elements in the airflow). Assembly 10 can be any compressor rectifier. Primarily, these are fixed compressor rectifiers with variable pitch. The stator assembly 10 can be part of the last stator stage (or rectifier) ​​at the compressor outlet (called the OGV, or "outlet guide vane"), which must rectify the flow to a purely axial velocity, and / or it can be part of the first fixed rectifier (in the direction of the flow).The assembly 10 can be upstream of a gooseneck 56, and more specifically, directly upstream of the gooseneck 56 (directly upstream meaning that the gooseneck is at the outlet of the blade pair 121, 124, without any other elements in the airflow). The invention is particularly well-suited to propulsion units 110 with variable pitch, due to the significant variations in angle of attack encountered (which are greater than in the case of propulsion units 110 without variable pitch). Within the scope of the invention, for any interval relating to a ratio and including the value 1, this value is excluded.

[0087] All the characteristics, technical effects, and advantages described for a tandem apply to all tandems in the stator assembly 10. The invention allows adaptation to the differential behavior of the airflow (particularly pronounced at 0% and 100% height) by giving the assembly the capacity to withstand deflection and incidence constraints (especially between the extrema, corresponding to the functional part of the blades). In the foregoing, the blades are defined at specific heights. The blade characteristics are smoothed between these heights. Any mathematical curve representing the blade characteristics over their entire height is continuous. The curve representing the blade characteristics is continuously differentiable over their entire height. The curve is of class C1.It will be obvious to a person skilled in the art that the invention is not limited to the achievements and examples illustrated and / or described above, but that its scope is more broadly defined by the claims introduced below.

Claims

22 Demands 1. Turbomachine compressor stator assembly (10) comprising - an internal support (52) and an external support (54), - two successive rows of stator blades defining a tandem configuration, the blades (121, 124) extending radially between the inner support (52) and the outer support (54), the blades (121, 124) comprising a leading edge (22), a trailing edge (24) and a chord (26) extending between the leading edge and the trailing edge, the rows comprising an annular row of upstream blades (121), and an annular row of downstream blades (124), located downstream of the upstream blades, in which, within the tandem, - the chord (26) of the upstream blade (121) is increasing with the height of the upstream blade, between the internal support (52) and the external support (54), - at 0% height of the upstream blade (121) between the internal support (52) and the external support (54), the chord (26) of the upstream blade is at least 1.9 times smaller than the chord of the upstream blade at 100% height of the upstream blade between the internal support (52) and the external support (54), - at 70% of the height of the upstream blade (121) between the internal support (52) and the external support (54), the chord (26) of the upstream blade is at least 1.2 times less than the chord of the upstream blade at 100% of the height of the upstream blade between the internal support (52) and the external support (54).

2. Assembly (10) according to the preceding claim, wherein, within the tandem, - at 30% of the height of the upstream blade (121) between the internal support (52) and the external support (54), the chord (26) of the upstream blade is at least 1.65 times smaller than the chord (26) of the upstream blade at 100% of the height of the upstream blade between the internal support (52) and the external support (54), - at 50% of the height of the upstream blade (121) between the internal and external supports, the chord (26) of the upstream blade is less than 1.35 times less than the chord (26) of the upstream blade at 100% of the height of the upstream blade between the internal support (52) and the external support (54).

3. Set (10) according to any one of the preceding claims, in which, within the tandem, - the ratio of the chord (26) of the downstream blade (124) to the chord of the upstream blade (121) decreases with the height of the blades between the internal support (52) and the external support (54), - at 0% height of the blades between the internal support (52) and the external support (54), the chord (26) of the downstream blade (124) is at least 2 times larger than the chord of the upstream blade (121), - at 20% height of the blades between the internal support (52) and the external support (54), the chord (26) of the downstream blade (124) is at least 1.5 times larger than the chord of the upstream blade (121), - between 50% and 100% of the height of the blades between the inner support (52) and the outer support (54), the ratio of the chord of the upstream blade to the chord of the downstream blade is between 0.8 and 1.

2.

4. Assembly (10) according to any one of the preceding claims, wherein, within the tandem, the rope (26) of the downstream blade (124) - is decreasing between 0% height between the internal support (52) and the external support (54) and 40% height between the internal support (52) and the external support (54), - is minimal between 40% and 60% of the height between the internal support (52) and the external support (54), - is increasing from 60% height between the internal support (52) and the external support up to 100% height between the internal support (52) and the external support (54).

5. Assembly (10) according to any one of the preceding claims, wherein, within the tandem, there is a 0% height difference between the internal support (52) and the support external (54) up to 20% height between internal support (52) and external support (54), the chord (26) of the downstream blade (124) is greater than the chord (26) at 100% height between internal support and external support.

6. Assembly (10) according to any one of the preceding claims, wherein, within the tandem, between 40% and 90% of the height between the inner support (52) and the outer support (54), the chord (26) of the downstream blade (124) is less than 95% of the chord (26) of the downstream blade at 100% of the height between the inner support (52) and the outer support (54).

7. Assembly (10) according to any one of the preceding claims, wherein, within the tandem, the blades further comprise o an intrados (16) and an extrados (18), o an equidistant line (21) between the intrados and the extrados, o a skeleton angle (29) between the tangent (28) to the equidistant line (20) and the driving axis (X), o a camber as the difference between the skeleton angle (29) at 95% of the chord (26) from the leading edge and the skeleton angle (29) at 5% of the chord (26) from the leading edge the camber ratio between the downstream blade (124) and the upstream blade (121) of a tandem is greater than 2 and less than 4 on at least one section along the height between the inner support (52) and the outer support (54).

8. Assembly (10) according to the preceding claim, wherein, on at least one cross-section of the upstream blade (121) of a tandem along the height between the inner support (52) and the outer support (54), the angle between the tangent to the intrados and the chord (26) has a minimum value between 5% of the leading edge and 95% of the chord, preferably the minimum value of the angle being positioned between 30 and 60% of the chord. 25 9. Assembly (10) according to one of the two preceding claims, wherein, on at least one cross-section of the upstream blade (121) of a tandem along the height between the inner support (52) and the outer support (54), the evolution of the dimensionless skeleton angle 95%” 5% with |3x%: the skeleton angle (29) at x% of chord, [35%: the skeleton angle (29) at 5% of chord (26), and [395%: the skeleton angle (29) at 95% of chord (26) has a deviation of less than 10% over the interval from 20% of chord (26) to 40% of chord (26) from the leading edge (22).

10. Assembly (10) according to any one of the three preceding claims, wherein, the blades comprise a thickness between the intrados (16) and the extrados (18), the upstream blade (121) has a thickness equivalent to at least 8% of the value of the chord (26) reached at 15% of the chord (26) from the leading edge, over at least one section along the height between the inner support (52) and the outer support (54). 1 1. Aircraft turbomachine low pressure compressor (120) comprising assembly (10) according to any one of the preceding claims.

12. Aircraft turbomachine (100) comprising the assembly (10) according to any one of the preceding claims or a compressor according to the preceding claim.

13. Turbomachine according to the preceding claim, comprising a propulsion unit (110) with variable pitch and driven by a speed reducer, the assembly (10) being downstream of the propulsion unit (110).

14. Turbomachine according to the preceding claim, in which the propulsion unit (110) is unfaired.

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