Rotating wheel for turbomachine, comprising blades equipped with a fin

Abstract

The invention relates to a rotating wheel (50) for a turbomachine, particularly for aircraft, comprising a plurality of blades (52), each blade comprising a blade (60) extending radially between a blade root (66) and a blade tip (68), axially between a leading edge (LA) and a trailing edge (BF), and tangentially between an upper surface (64) and an lower surface (62), two adjacent blades being separated by an inter-blade distance (D), characterized in that each blade (52) has a vane (70) arranged as a blade tip, said vane extending tangentially from the lower surface of the blade over a maximum width of between 5 and 10% of the inter-blade distance. Figure for the abstract: Figure 5

Description

Title of the invention: TURBOMACHINE TURPOSING WHEEL COMPRISING BLADES EQUIPPED WITH A FIN Technical field of the invention

[0001] The present invention relates to the field of aircraft turbomachinery. It relates more particularly to compressor blades for turbomachinery. Technical background

[0002] Aeronautical turbomachinery is conventionally composed, from upstream to downstream in the direction of gas flow, of a fan, one or more compressor stages, for example a low-pressure compressor and a high-pressure compressor, a combustion chamber, one or more turbine stages, for example a high-pressure turbine and a low-pressure turbine, and a gas exhaust nozzle. The compressor(s) are implemented in the form of a plurality of rotating blades in front of a plurality of fixed blades called stators. The rotating blades are arranged regularly around the periphery of a disk driven by the turbomachine rotor, and their blades extend radially between the rotor disk and a casing that closes the air stream.

[0003] Each movable blade has an underside on which the air in the airflow is under positive pressure relative to the average pressure surrounding the blade, and an underside on which the air is under negative pressure relative to this average pressure. Consequently, an air circuit is established at the outer end of the blade, which tends to draw air from the underside to the upperside through the gap between the blade and the housing. This air circulation, as is known, develops along the entire chord of the blade and takes the form of a vortex, called a clearance vortex, which propagates downstream of the trailing edge of the blade.

[0004] The presence of this vortex disrupts the flow in the downstream stages of the compressor and creates losses that are detrimental to the compressor's efficiency. It would therefore be desirable to eliminate this vortex or at least reduce the airflow it carries.

[0005] In the case of small axial compressors, whose impellers can be very small, it is difficult or even impossible to maintain a clearance size compatible with a large pumping margin. Indeed, the flow in the impeller head clearance can quickly become the primary cause of instability if it exceeds values ​​on the order of 2% of the clearance height to blade height ratio.

[0006] Attempts have been made to try to control this vortex and thus improve the pumping margin, particularly in the case of high blade tip clearance, such as by An example of this is the treatment applied to the casing surrounding the compressor, or the creation of "trenches," i.e., cavities machined into the casing. These casing treatments modify the clearance flow either by disrupting the formation of (axissymmetric) clearance vortices or by diverting some of the flow within the clearance from high-pressure areas near the blade trailing edge to lower static-pressure areas near the leading edge. An example of such treatments is described in the applicant's patent application published under number FR 2940374. All of these treatments have the disadvantage of generating additional costs for the turbomachine's construction and can degrade compressor efficiency at certain operating points.

[0007] To address the aforementioned problems, patent applications have also been filed to improve the pumping margin when it is due to backflow by attempting to reduce the impact of this vortex on the efficiency of a compressor or turbine stage. These applications propose modifying the shape of the blades, particularly by altering the shape of the leading edge, that is, by changing its sweep angle between the root and the tip of the blade along this leading edge. For example, document WO 2012 / 080669 A1 describes a turbomachine blade with a particular tip geometry, notably featuring a double reversal of its curvature direction in the outer radial third of the blade. Such a design aims to improve aerodynamic losses due to leakage flow at the blade tip resulting from radial clearance between the blades and the casing.This radial clearance is necessary to prevent contact between the blade and the housing, which could occur at high speeds. Indeed, in this design, the blades cannot withstand contact with the housing as this would damage them.

[0008] The invention aims to provide an alternative to previous solutions, addressing at least some of these drawbacks. In particular, one of the objectives of the present invention is to provide a blade exhibiting good stability at the opening of the clearance at the blade tip, thereby improving the pumping margin without reducing the clearance, which is assumed to be constrained to a relatively high value on the order of 2% of the clearance height to blade height ratio. Summary of the invention

[0009] The invention relates to a movable wheel for a turbomachine, in particular for an aircraft, comprising a plurality of blades, each blade comprising a blade extending radially between a blade root and a blade tip, axially between a leading edge and a trailing edge and tangentially between an extrados face and an intrados face, two adjacent blades being separated by an inter-blade distance.

[0010] According to the invention, each blade comprises a fin arranged at the blade head, said blade extending tangentially from the lower surface of the blade over a maximum width of between 5 and 10% of the inter-blade distance.

[0011] Thus, the invention provides a simple solution to at least some of the drawbacks described above. Specifically, the invention proposes a rotating impeller equipped with blades having a narrow fin at the apex on the underside and a thin apex thickness located at the radius of the clearance, thereby reducing the flow rate through the clearance. Such a rotating impeller improves the pumping margin without reducing the clearance, which is assumed to be limited to a relatively high value of approximately 2% of the clearance height to blade height ratio, particularly when the blades are small, i.e., less than 30 mm.

[0012] The invention thus makes it possible to gain margin in pumping without reducing the efficiency of the turbomachine.

[0013] Indeed, the geometry of the blade head creates an "obstacle" to the radial airflow. The formation of leakage vortices at the head is prevented, resulting in improved compressor efficiency and therefore improved turbomachinery efficiency.

[0014] The movable wheel according to the invention may comprise one or more of the following features, taken individually or in combination with each other, according to all technically possible combinations: - the blade extends radially along a span direction between the blade root and the blade tip and the vane extends radially between an inner face and an outer face, the outer face being substantially perpendicular to the span direction of the blade and the inner face being concave; - the fin has a connecting end of the fin to the intrados face and a free end, the thickness of the blade in the radial direction decreases from the connecting end to the free end; - the thickness of the free end of the fin is less than 0.2mm; - the fin extends axially between a first end and a second end arranged between the leading edge and the trailing edge of the blade, the first end being arranged at a distance from the leading edge of the blade, the second end being arranged at a distance from the trailing edge of the blade, and the first end being closer to the leading edge of the blade than the second end; - the fin has an axial length between the first end and the second end between 5% and 95% of the distance between the leading edge and the trailing edge of the fin; - The fin comprises a first portion, a second portion, and a third portion, the second portion being arranged between the first and third portions, and the fin has a constant width in the second portion, and an increasing width in the first portion from the first end to the second portion and a decreasing width in the third portion of the second portion towards the second end, the width being the tangential extension dimension of the fin from the intrados face of the blade.

[0015] The invention also relates to a compressor for a turbomachine, in particular for an aircraft, comprising at least one movable wheel according to the invention and as described above.

[0016] The invention also relates to a turbomachine, particularly for aircraft, comprising at least one rotating wheel according to the invention and as described above, or such a compressor according to the invention and as described above. Brief description of the figures

[0017] The invention will be better understood and other features and advantages will become apparent upon reading the following detailed description, which includes embodiments given by way of illustration with reference to the accompanying figures and presented as non-limiting examples, which may serve to complete the understanding of the present invention and the explanation of its implementation and, where appropriate, contribute to its definition, on which: - Fig. 1 represents a schematic axial (or longitudinal) cross-sectional view of a turbomachine to which the invention applies; - [Fig.2] is a partial schematic cross-sectional view of a compressor of the turbomachine in [Fig.1]; - [Fig.3] schematically represents a partial cross-sectional view of a compressor according to the state of the art; - Fig. 4 illustrates a three-dimensional view of a movable wheel blade according to the invention; - [Fig.5] represents a partial cross-sectional view of a compressor according to the invention equipped with blades of [Fig.4]; - Fig. 6 represents a sectional view of two adjacent blades of a rotating wheel according to the invention; - Figure 7 is a graph illustrating the improvement in the compression ratio of a compressor rotor equipped with moving blades according to Figure 6; and - [Fig.8] is a graph illustrating the improvement in efficiency of a compressor rotor equipped with moving blades according to [Fig.6].

[0018] Elements having the same functions in the different implementations have the same references in the figures. The figures are not drawn to scale. In particular, the thicknesses are enlarged to facilitate reading the figures. Detailed description of the invention

[0019] The invention relates to a turbomachine intended to be mounted on an aircraft, such as an airplane or a helicopter. The turbomachine may be a turboengine, a turbojet, for example a turbomachine equipped with a shrouded fan (turbofan) or a turboprop, for example a propulsion unit equipped with an unshrouded propeller (“open rotor”, “USF” for “Unducted Single Fan” or “UDF” for “Unducted Fan”).

[0020] Fig. 1 represents an example of such an aircraft turbomachine 10. In the illustrated example, the turbomachine is a twin-spool, twin-body turbomachine which has a longitudinal axis C parallel to the X axis.

[0021] Throughout the figures, the X direction denotes the direction of the C axis of the turbomachine, while the Y and Z directions are two radial directions orthogonal to each other. Furthermore, the terms "internal" and "external" refer to a position relative to the axis of rotation of a turbomachine or the longitudinal axis C. The axial direction, denoted X, corresponds to the direction along the C axis of rotation of the turbomachine. The radial direction, denoted R, is perpendicular to the axis of rotation. The tangential direction, denoted T, is perpendicular to the axial X and radial R directions. Upstream and downstream refer to the main flow direction of the flow within the turbomachine.

[0022] The turbomachine 10 comprises, from upstream to downstream, with reference to the direction of gas flow (see arrows), an air inlet 20, a low-pressure compressor 22, a high-pressure compressor 24, an annular combustion chamber 26, a high-pressure turbine 28 and a low-pressure turbine 30.

[0023] The high-pressure turbine 28 is connected to the high-pressure compressor 24 by a high-pressure shaft so as to form a high-pressure body, while the low-pressure turbine 30 is connected to the low-pressure compressor 22 by a low-pressure shaft so as to form a low-pressure body, so that each turbine drives the associated compressor in rotation around the axis of the turbomachine X under the effect of the thrust of the gases from the combustion chamber 26.

[0024] The turbomachine 10 further comprises, upstream of the low-pressure compressor 22, a fan 32 which is arranged here directly downstream of an air inlet cone. The fan 32 comprises a ring of fan blades 34 rotating about the axis C of the turbomachine. The fan 32 is here enclosed by a nacelle 36.

[0025] Furthermore, in the illustrated example, the turbomachine 10 defines a primary flow VI intended to be traversed by a primary flow Fl, and a secondary flow V2 intended to be traversed by a secondary flow F2 located radially outwards with respect to the primary flow. The flow F from the fan is split at a flow separation nozzle 40 of an intermediate casing 42. The intermediate casing 42 is usually interposed between the low-pressure compressors pressure 22 and high pressure 24.

[0026] In operation, air flows through the blower 32 and a first part of the airflow, the primary flow Fl, is routed through the low-pressure compressor 22, where the primary airflow Fl is straightened, then through the high-pressure compressor 24 where the primary airflow Fl is compressed and sent to the combustion chamber 26. The hot combustion products from the combustion chamber 26 are used to drive the high-pressure turbines 28 and low-pressure turbines 30 and thus produce the thrust of the turbomachine 10.

[0027] Figure 2 is a simplified partial schematic cross-sectional view of a compressor of the turbomachine of Figure 1. This refers to the low-pressure compressor 22, but the principles of this application can also be applied to the high-pressure compressor 24.

[0028] The compressor 22 includes a rotor 46 which rotates around an axis coinciding with the axis of rotation C of the turbomachine and which is coupled to the blower 32.

[0029] The low-pressure compressor 22 comprises a succession of stages, where each stage comprises a moving wheel 50 or rotor comprising several moving blades 52 carried by a disc and a wheel of stator blades 54 carried by an annular ferrule of the separation nozzle 40. The stator blades 54 may be variable pitch angle blades.

[0030] The compressor 22 includes a housing 56. The housing 56 may generally have a circular or tubular shape. It may be composed of several angular segments or be a single piece. It may be made of composite material.

[0031] The rotor blades 52 extend essentially radially along a span direction. In the illustrated example, the blades 52 have a mounting platform for a disc. Alternatively, the movable blades 52 can be integral with the disc to form a movable wheel.

[0032] The external radial end of the movable blades 52 comes into contact with the housing 56.

[0033] Figure [Fig. 3] is a partial view in a plane perpendicular to the longitudinal axis C of a blade according to the prior art. The blade 52A comprises a blade 60A and fastening elements (not shown). The blade 60A comprises a leading edge BA, a trailing edge BF, an intrados face 62A and an extrados face 64A. The blade 60A extends radially between a blade root 66A and a blade tip or apex 68A. The radial height of the blade is denoted H.

[0034] The vane 52A and the disc 70 rotate in a direction of rotation F4 to compress the primary airflow FL

[0035] At the level of the blade head 68A, a radial clearance J is provided between the blade 52A and the housing 56, in order to ensure rotation of the blade 52A without friction on the housing 56, or to minimize the probabilities of contact between the blade 52A and the housing 56. This clearance J results in leakage flow (solid arrows). Indeed, an airflow with a radial component along the lower surface reaches the clearance and, following the passage of blade 52A, generates vortices that propagate axially downstream and degrade the flow downstream of blade 52A. Known geometries exhibit a clearance J that is 0.8% to 2% of H, depending on the blade's position in the compressor (larger clearance downstream).

[0036] Figure 4 illustrates a three-dimensional view of a blade 52 for a moving wheel according to the invention. This differs from the blade 52A of Figure 3 in its geometry and in particular in the geometry of its head.

[0037] As with the rotor blade 52A of [Fig.3], the rotor blade 52 according to the invention comprises a blade 60 extending radially between a blade root 66 and a blade tip 68 along the span direction substantially parallel to the radial direction R. The blade 60 also extends axially between a leading edge BA and a trailing edge BF and tangentially between an extrados face 64 and an intrados face 62. Furthermore, two adjacent blades 52 of the moving wheel according to the invention are separated by an inter-blade distance D (illustrated in [Fig.6]) representing the minimum distance between 2 adjacent profiles and in the absence of a fin, this distance is also called the col.

[0038] Each blade 52 further comprises a fin 70 arranged at the blade head. This fin 70 extends tangentially from the lower surface of the blade. More precisely, the fin 70 extends tangentially from a connecting end 72 of the fin to the lower surface of the blade towards a free end 74 downstream of the blade. Furthermore, the fin 70 extends radially between an inner face 75 and an outer face 76, and axially between a first end 78 and a second end 79 arranged between the leading edge BA and the trailing edge BF of the blade. More precisely, the first end 78 is arranged at a distance from the leading edge BA of the blade 60, and the second end 79 is arranged at a distance from the trailing edge BF of the blade 60, the first end 78 being closer to the leading edge BA of the blade 60 than the second end 79. Thus, the fin 70 advantageously begins on the lower surface 62 at the reference point 80, corresponding to the intersection between the throat and the lower surface.

[0039] According to the invention, the blade 70 extends tangentially from the lower surface 62 of the blade over a maximum width denoted d between 2 and 10% of the interblade distance D.

[0040] As illustrated in [Fig.5], the outer face 76 is preferably substantially perpendicular to the span direction, denoted E, of the blade 60 and the inner face 75 is preferably concave. The fin thickness is defined as the fin dimension 70 according to the radial direction R. In other words, the thickness of the fin is the distance between the outer face 76 and the inner face 75 of the fin 70 along the radial direction R. According to the invention, the thickness of the fin 70 along the radial direction R advantageously decreases from the connecting end 72 to the free end 74. The thickness of the free end 74 of the fin is as thin as possible taking into account the mechanical constraints and the external face 76 is at a distance from the housing equal to the imposed clearance J, in order to drive the maximum flow towards the inside of the vein. Preferably, the thickness of the free end 74 of the blade is less than 1% of the blade height. For example, for a blade less than 30 mm, the thickness of the free end 74 of the blade is less than 0.2 mm.

[0041] As illustrated in [Fig. 5], such a fin 70 diverts part of the game flow. Indeed, since the game flow comes mainly from the intrados 62, the presence of the fin 70 prevents part of the flow from passing into the game by diverting it towards the foot 66 of the blade.

[0042] Figure 6 shows a cross-sectional view of two adjacent movable blades 52 of a movable wheel according to the invention. Each blade 70 has an axial length L between the first end 78 and the second end 79 of between 5% and 95% of the distance between the leading edge BA and the trailing edge BF of the blade; this distance is also called the chord.

[0043] This [Fig. 6] represents a particular application of the invention. In particular, The fin 70 comprises a first portion PI, a second portion P2 and a third portion P3, the second portion P2 being arranged between the first portion PI and the third portion P3. The first portion P1 extends axially from the first axial end 78 of the fin to the second portion P2, up to the point M separating the first and second portions. The second portion P2 extends axially from point M to the point N separating the second and third portions. The third portion P3 extends axially from the point N to the second axial end 79 of the fin 70.

[0044] According to the illustrated example, the blade 70 has a constant width in the second portion P2 between 2 and 10% of the inter-blade distance D and preferably substantially equal to 5% of the inter-blade distance D. The fin 70 has an increasing width in the first portion PI from the first end 78 to the second portion P2 and a decreasing width in the third portion P3 from the second portion P2 to the second end 79. As a reminder, the width is the tangential extension dimension of the fin from the intrados face 62 of the blade 60 downstream.

[0045] The maximum width of the fin profile 70, i.e. the second portion P2 must be arranged closer to the trailing edge BF than to the leading edge BA of the blade, beyond the position of the throat of the basic 80 profile of the blade in order to preserve as much as possible the flow passage section at the top.

[0046] Furthermore, in the illustrated example, the extrados face 64 is unchanged compared to the extrados face 64 of a blade according to the prior art and the collection zone 82 arranged between the attack BA and the neck D remains identical to that of the basic blade.

[0047] The modified blades according to the invention have been evaluated and compared with the bladeless blades of the prior art by the inventors. Navier Stokes 3D calculations allowing visualization of radial velocity contours at the same abscissa and with the same downstream back pressure on a basic blade and on a blade with fin according to the invention, make it possible to demonstrate that the flow which passes through the gap with the basic blade comes from a large area whereas with the fin only the part very close to the outer wall of the casing participates in the flow in the gap.

[0048] Thus, such a mobile wheel equipped with bladed vanes makes it possible to gain several points of margin in pumping without degrading the efficiency on the operating line.

[0049] Figures 7 and 8 show the performance improvement, obtained by a three-dimensional Navier-Stokes calculation, of a compressor rotor according to the invention compared to a conventionally manufactured rotor, i.e., with moving blades without vanes. The two curves represent the points obtained at the same rotational speed for a prior art rotor (connected circles on the graphs) and a rotor according to the invention (crosses on the graphs). The abscissa represents the evolution of the airflow through the grid, and the ordinates indicate the compression ratio obtained ([Fig. 7]) and the efficiency obtained ([Fig. 8]) for the various calculation points. In [Fig. 7], the point corresponding to the maximum compression ratio represents the point located on the pumping line of this rotor, and the rightmost point represents the point on the operating line, which in this case corresponds to the point of maximum efficiency.The invention thus makes it possible to gain several percentage points of margin without degrading the efficiency on the operating line. Furthermore, mechanical calculations showed that no stress concentration was present in the blade area. The maximum stress increased slightly with the addition of mass at the tip, but this maximum stress remained at the blade root, as with a conventional blade in the prior art, i.e., without a blade. Furthermore, the frequency content of a bladed turbine is necessarily slightly different from that of a conventional bladeless turbine. The 1F and 1T frequencies decrease somewhat, and certain band-mode frequencies may increase because the head cut is more rigid. Therefore, adjusting the stacking and thicknesses helps to avoid... Frequency coincidences is therefore slightly different with a fin, but the variable thickness law of the fin offers new parameters to modify the frequencies so that in some cases the mechanical design is facilitated.

[0050] The invention as described advantageously provides a rotating impeller equipped with blades having narrow, narrow apex vanes on the underside, with a thin apex thickness that reduces the flow passing through the gap between the housing and the blade. Thus, the invention increases pumping margin without reducing the efficiency of the compressor and turbine.

[0051] Obviously, the invention is not limited to the embodiments described above and provided solely by way of example. It encompasses various modifications, alternative forms and other variants that a person skilled in the art may consider within the scope of the invention, and in particular all combinations of the different modes of operation described above, which may be taken separately or in combination. In particular, the invention can be modified in various ways by adjusting the blade width distribution along the profile according to the characteristics of the base blade (without a blade), provided that the intake area is maintained and the width parameters are optimized based on mechanical constraints and the desired gain. The invention is also compatible with treatments applied to the housing surrounding the compressor and / or modifications to the blade shape, particularly the leading edge shape mentioned previously. Indeed, the invention can be combined with improvements to the stacking of the profiles, such as axial tilting of the blade tip upstream or tangential tilting towards the upper surface, or with modifications to the profile alignment at the tip. The gains from all these improvements will then be cumulative, as applicable.

Claims

Claims

1. A mobile wheel (50) for a turbomachine, in particular an aircraft, comprising a plurality of blades (52), each blade comprising a blade (60) extending radially between a blade root (66) and a blade head (68), axially between a leading edge (BA) and a trailing edge (BF) and tangentially between an extrados face (64) and an intrados face (62), two adjacent blades being separated by an inter-blade distance (D), characterized in that each blade (52) comprises a fin (70) arranged at the blade head, said fin extending tangentially from the intrados face of the blade over a maximum width of between 5 and 10% of the inter-blade distance.

2. A movable wheel according to claim 1, wherein the blade (60) extends radially in a span direction (E) between the blade root (66) and the blade head (68) and the fin (70) extends radially between an inner face (75) and an outer face (76), the outer face being substantially perpendicular to the span direction of the blade and the inner face being concave.

3. A mobile wheel according to claim 2, wherein the fin (70) comprises a connecting end (72) of the fin to the intrados face (62) and a free end (74), the thickness of the fin (70) in the radial direction (R) decreases from the connecting end (72) towards the free end (74).

4. A movable wheel according to claim 3, wherein the thickness of the free end (74) of the fin (70) is less than 0.2mm.

5. A movable wheel according to one of the preceding claims, wherein the fin (70) extends axially between a first end (78) and a second end (79) arranged between the leading edge (BA) and the trailing edge (BF) of the blade (60), the first end (78) being arranged at a distance from the leading edge (BA) of the blade, the second end (79) being arranged at a distance from the trailing edge (BF) of the blade, and the first end (78) being closer to the leading edge (BA) of the blade than the second end (79).

6. A moving wheel according to claim 5, wherein the blade (70) axially has a length (L) between the first end (78) and the second end (79) of between 5% and 95% of the distance between the leading edge (BA) and the trailing edge (BF) of the blade (60).

7. A movable wheel according to claim 5 or 6, wherein the fin (70)

8.

9. comprises a first portion (PI), a second portion (P2) and a third portion (P3), the second portion (P2) being arranged between the first portion (PI) and the third portion (P3) and in which the fin (70) has a constant width in the second portion (P2), an increasing width in the first portion (PI) from the first end towards the second portion and a decreasing width in the third portion (P3) from the second portion towards the second end, the width being the tangential extension dimension of the fin from the intrados face (62) of the blade. Compressor (22) for a turbomachine, in particular for an aircraft, comprising at least one mobile wheel according to one of the preceding claims. Turbomachine (10), in particular for an aircraft, comprising at least one moving wheel according to one of claims 1 to 7 or at least one compressor (22) according to the preceding claim.

Images