Inter-turbine housing for turbine engine, turbine engine assembly, turbine engine and method for positioning splitter blades within inter-turbine housing

Abstract

The invention relates to an inter-turbine housing (8) for a turbine engine of the turbine blade frame type, which housing serves as a turbine distributor in such a turbine engine, the inter-turbine housing comprises an inner shroud (9), an outer shroud (10), a plurality of arms (11) extending between the inner shroud and the outer shroud, and at least one set of N splitter blades (12) positioned circumferentially between two consecutive arms. Each splitter blade has an intermediate height axial chord length that is shorter than the height axial chord length of the arm. The two consecutive arms define a reference position for each of the N splitter blades. The reference positions are uniformly distributed in the circumferential direction between the two continuous arms. At least one splitter blade (12-1) of the set of N splitter blades is circumferentially offset from its reference position. The invention also relates to a turbine engine assembly comprising an inter-turbine housing and a turbine (7) extending downstream of the inter-turbine housing (8), and comprising at least one radially extending rotor blade (13). The invention also relates to a turbine engine comprising the turbine engine assembly. A method for positioning splitter blades within an inter-turbine housing is also disclosed.

Description

Technical Field

[0001] The present disclosure generally relates to an inter-turbine casing for a turbine blade frame (TVF) type turbine that performs the function of a turbine distributor in such a turbine. Background Art

[0002] In a manner known per se, the turbomachine comprises an inter-turbine housing arranged between a high-pressure turbine housing and a low-pressure turbine housing in the turbomachine. The inter-turbine housing comprises a fairing comprising an inner shroud and an outer shroud which together define a flow path between the high-pressure turbine and the low-pressure turbine, and arms extending radially between the inner shroud and the outer shroud.

[0003] The inter-turbine casing has an aerodynamic function, acts as a stator to deflect the incident flow from the high-pressure turbine, has a structural function to transmit mechanical forces between the inner shroud and the outer shroud, and has an integration function for the service channel. Thus, the fairing can have a multi-profile construction, which includes, in addition to the arms, splitter blades, the chord size of which is reduced compared to the arms, which are thicker and have a longer chord length. Thus, the splitter blades and the downstream part of the arms ensure the aerodynamic function, while the arms ensure the structural function and the integration function.

[0004] However, the wake generated by the blades of the inter-turbine casing (i.e., thick arms and splitter blades) is particularly wide and energetic. Specifically, the significant profile difference between the arms and splitter blades leads to significant wake differences, which causes significant distortions in the flow downstream of the inter-turbine casing, which may undermine the performance of the low-pressure turbine (aerodynamic losses, shedding), affect its mechanical strength (periodic excitation), and even cause integration problems of the low-pressure turbine (size of the low-pressure turbine).

[0005] Therefore, there is a real need to overcome the above mentioned drawbacks by proposing a solution to improve the aerodynamic efficiency and thus the efficiency of the low-pressure turbine in a turbomachine comprising an inter-turbine casing. Summary of the invention

[0006] The present disclosure relates to an inter-turbine casing for a turbomachine, comprising: an inner shield centered on the central axis; an outer shroud coaxially surrounding the inner shroud; a plurality of arms, each arm extending between the inner shroud and the outer shroud, having a leading edge and a trailing edge, and having a mid-height axial chord length; and at least one set of N splitter vanes, the splitter vanes being circumferentially positioned between two consecutive arms, each splitter vane extending between the inner shroud and the outer shroud, having a leading edge and a trailing edge, and having a mid-height axial chord length that is shorter than a mid-height axial chord length of the arm; wherein the two consecutive arms define reference positions for each of the N splitter blades, the reference positions being evenly circumferentially spaced between the two consecutive arms; and At least one splitter blade in the group of N splitter blades is circumferentially offset relative to its reference position.

[0007] In other words, in the reference configuration, the azimuth angle Ai of the reference position of the i-th splitter blade in the set of N splitter blades, i.e. its angular position around the central axis, can be written as: i =A B1 +(A B2 -A B1 ) / (N+1), where A B1 is the azimuth of the first arm, A B2 is the azimuth angle of the second arm, defining the set of N splitter blades.

[0008] Thus, in this configuration according to the invention, unlike conventional configurations typically found in rotary machines, the splitter blades are not all evenly arranged between the arms.

[0009] In fact, the inventors have observed that, according to this reference configuration, with arms and splitter vanes evenly spaced about the central axis, the flow through the inter-turbine casing is significantly distorted in velocity and direction. Conversely, the inventors have determined that offsetting all or some of the splitter vanes relative to their generally accepted reference positions can reduce flow distortions, thereby improving performance downstream of the turbine.

[0010] The present invention is therefore the result of technical research aimed at significantly improving the performance of turbines and, in this sense, contributing to reducing the environmental impact of aviation.

[0011] In some embodiments, the plurality of arms comprises 4 to 20 arms.

[0012] In some embodiments, the arms are evenly distributed around the central axis. Therefore, their distribution is axisymmetric.

[0013] In some embodiments, all arms have the same profile.

[0014] In some embodiments, at least one arm is hollow, the at least one arm including a passageway to allow services for the turbine to pass through.

[0015] In some embodiments, the set of N splitter blades includes 1 to 4 splitter blades.

[0016] In some embodiments, the inter-turbine casing includes a set of splitter blades located between each consecutive arm.

[0017] In some embodiments, each set of splitter blades includes the same number of splitter blades.

[0018] In some embodiments, the splitter blades are arranged in the same manner relative to each other in each set of splitter blades. Thus, the configuration of each set of splitter blades, ie, the combination of the respective arrangements of each of their blades, constitutes a single pattern that is repeated identically between the arms.

[0019] In some embodiments, all splitter blades have the same profile.

[0020] In some embodiments, the mid-height axial chord length of the splitter vane is at least 2 times shorter than the mid-height axial chord length of the arm, preferably at least 3 times shorter.

[0021] In some embodiments, the maximum thickness of the splitter blade is less than the maximum thickness of the arm.

[0022] In some embodiments, the maximum thickness of the splitter blade is at least 2 times smaller than the maximum thickness of the arm, preferably at least 3 times smaller.

[0023] In some embodiments, the profile of at least the downstream portion of the splitter vane is the same as the profile of the downstream portion of the arm.Thus, at least near their trailing edges, the aerodynamic behavior of the arm and the splitter vane is similar, which reduces flow distortion.

[0024] In some embodiments, the trailing edge of the splitter vane is circumferentially aligned with the trailing edge of the arm about the central axis.

[0025] In some embodiments, the leading edge of the splitter vane is disposed further downstream than the leading edge of the arm.

[0026] In some embodiments, at least one of the group of N splitter blades adjacent to the arm is circumferentially offset relative to its respective reference position. This is preferably the case for both splitter blades in the group adjacent to the arm. This reduces distortion caused by differences in the profile of the arm.

[0027] In some embodiments, all splitter blades in the set of N splitter blades are circumferentially offset relative to their respective reference positions.

[0028] In some embodiments, the absolute value of the circumferential offset of the at least one splitter blade circumferentially offset relative to its reference position is less than 0.25×Δref, where Δref is the angular deviation between two consecutive reference positions. Preferably, no splitter blade has an absolute value of circumferential offset relative to its reference position greater than this limit. In fact, the inventors have determined that the optimal offset region lies within this range.

[0029] In some embodiments, at least one splitter blade in the set of N splitter blades has a thickness different from the other splitter blades in the set of N. Thus, in this case, the TE (trailing edge) trace stack of the blade cross section in question does not overlap with the TE-trace stack of the arm cross section.

[0030] In some embodiments, at least one splitter blade of the set of N splitter blades has a different geometry than the other splitter blades of the set of N splitter blades, in particular by having a different stacking law. Also in this case, the TE (trailing edge) trace stacking of the blade cross section in question does not overlap with the TE trace stacking of the arm cross section.

[0031] The present disclosure also relates to a turbine assembly, comprising: The inter-turbine casing according to the aforementioned embodiment, and A turbine wheel extends downstream of the inter-turbine housing and includes at least one radially extending moving blade.

[0032] The present disclosure also relates to a turbine, comprising a turbine assembly according to any one of the above embodiments.

[0033] The present disclosure also relates to a method for positioning a splitter blade in a turbine inter-turbine casing according to any one of the above embodiments, comprising the following steps: providing a turbine inter-turbine casing; positioning splitter vanes within the inter-turbine housing at their respective reference positions; evaluating a parameter of flow through the inter-turbine casing on either side of a given splitter vane and determining a reference distortion of the parameter; moving the given splitter blade to one or more azimuthal positions circumferentially offset from its reference position; and For each of these offset azimuth positions: - evaluating parameters of the flow on either side of said given splitter blade (12-1); - determining the distortion (Dd') of said parameter; and - Compare the shifted distortion (Dd') with the reference distortion (Dd); Positioning the splitter vanes at an offset azimuth position within the inter-turbine casing reduces distortion of parameters of the flow.

[0034] It is understood here that the steps of positioning, moving and evaluating parameters can be performed experimentally or numerically using numerical simulations. An offset position is then retained for a given splitter vane which can reduce or even minimize the distortion of the flow parameters.

[0035] In some embodiments, the flow parameter is evaluated based on the azimuth position in the downstream radial plane.

[0036] In some embodiments, the step of evaluating the shifted flow parameters is performed for several different offset positions of a given splitter vane within the survey range.

[0037] In some embodiments, the magnitude of the survey range is greater than 0.1×Δref and less than 0.25×Δref, where Δref is the angular deviation between two consecutive reference positions.

[0038] In some embodiments, these steps are repeated successively for each splitter blade in the set of N splitter blades.

[0039] In some embodiments, the parameter of the flow being evaluated is the flow velocity or the angle of the flow relative to the central axis.

[0040] In the present disclosure, the terms "longitudinal", "transverse", "lower", "upper" and their derivatives are defined relative to the main direction of the blade; the terms "axial", "radial", "tangential", "inner", "outer" and their derivatives are defined relative to the central axis of the inter-turbine casing, that is, the main axis of the turbine; the "axial plane" refers to the plane passing through the main axis of the turbine, while the "radial plane" refers to the plane perpendicular to the main axis; the terms "upstream" and "downstream" are defined relative to the air circulation in the turbine; finally, the terms "front" and "rear" refer to the circumferential direction when proceeding in the clockwise direction.

[0041] The above features and advantages as well as other features and advantages will appear after reading the following detailed description of exemplary embodiments of the inter-turbine housing and proposed method. The detailed description refers to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The drawings are schematic diagrams, primarily intended to illustrate the principles of the present disclosure.

[0043] In the drawings, the same elements (or parts of elements) are labeled with the same reference numerals from one drawing to another.

[0044] [ Figure 1 ] Figure 1 is an axial section through a turbine according to the invention.

[0045] [ Figure 2 ] Figure 2 is a cross-sectional view of an example turbine assembly including an inter-turbine casing and a turbine.

[0046] [ Figure 3 ] Figure 3 yes Figure 2 A partial perspective view of an example of a turbine assembly.

[0047] [ Figure 4 ] Figure 4 is a graph showing the flow velocity versus azimuthal position for the reference and offset structures.

[0048] [ Figure 5 ] Figure 5 is a graph showing the variation of flow angle with azimuthal position for the reference and offset structures. DETAILED DESCRIPTION

[0049] In order to make the present disclosure more specific, an example of the inter-turbine casing is described in detail below with reference to the accompanying drawings. It should be noted that the present invention is not limited to this example.

[0050] A turbofan engine 1 (usually an aircraft turbine 1) generally includes a fan 2, a main annular flow path I, and a secondary annular flow path II from upstream to downstream along the gas flow direction. Therefore, the air sucked by the fan 2 is divided into a main flow circulating in the main flow path I and a secondary flow concentric with the main flow and circulating in the secondary flow path II.

[0051] The main flow path I passes through a body comprising one or more compressor stages, such as a low-pressure compressor 3 and a high-pressure compressor 4, a combustion chamber 5, one or more turbine stages, such as a high-pressure turbine 6 and a low-pressure turbine 7 separated by an inter-turbine casing 8, and an exhaust nozzle.

[0052] In the present application, upstream and downstream are defined relative to the normal flow direction of the gas in the turbine 1. Furthermore, the axis X is referred to as the axis of rotation of the rotor of the low-pressure turbine 7, which coincides with the axis of extension of the turbine 1. The axial direction corresponds to the direction of the axis X, and the radial direction is a direction perpendicular to and passing through the axis X. Furthermore, the circumferential direction corresponds to a direction perpendicular to the axis X but not passing through the axis.

[0053] The inter-turbine casing 8 comprises an inner shroud 9 and an outer shroud 10 substantially coaxial with the axis X, and a fixed blade assembly comprising a plurality of arms 11, which together form a ring gear. The arms 11 extend from the inner shroud 9 to the outer shroud 10 and may be substantially radial with respect to the axis X. Each arm 11 comprises a structural portion configured to transmit mechanical forces between the inner shroud 9 and the outer shroud 10, the structural portion being housed in an aerodynamically shaped wall.

[0054] The aerodynamic wall thus makes it possible to straighten the flow at the outlet of the high-pressure turbine 6 and to improve the supply of the low-pressure turbine 7 located immediately downstream of the inter-turbine casing 8 .

[0055] The inter-turbine housing 8 may in particular comprise four to twenty arms 11. In the present example, the inter-turbine housing 8 comprises ten arms 11. Preferably, these arms 11 are evenly spaced about the axis X. The inter-turbine housing 8 further comprises a plurality of splitter blades 12 circumferentially positioned between the arms 11: thus, a set of one or more splitter blades 12 is provided between each arm 11. It should be noted that, conventionally, the chord of each splitter blade 12 is shorter than the chord of each arm 11. The trailing edge 12f of each splitter blade 12 is circumferentially aligned with the trailing edge 11f of each arm 11; thus, the leading edge 11a of the arm 11 is located further upstream than the leading edge 12a of the splitter blade 12. Furthermore, preferably, the downstream portion of the arm 11 has a profile corresponding to at least one downstream portion of the splitter blade 12.

[0056] The inter-turbine casing 8 may comprise from one to four splitter blades 12 between consecutive arms 11. Preferably, each set of splitter blades 12 comprises the same number of blades 12. In the present example, three splitter blades 12 are arranged between each arm 11.

[0057] The low-pressure turbine 7 comprises a plurality of turbine stages in a manner known per se, each turbine stage comprising at least one moving blade 13. The low-pressure turbine 7 may comprise at least three turbine stages, for example between three and five turbine stages in the example of a turbine whose fan 2 is driven via a reduction mechanism. Since the low-pressure turbine 7 is conventional, it will not be described in detail herein.

[0058] Each arm 11 has a mid-height axial chord 14. The mid-height axial chord 14 of a given arm 11 is defined by a mid-height line 15, which corresponds to a (imaginary) line contained in a plane perpendicular to the axis X and includes all points located between the inner shroud 9 and the outer shroud 10, and between the inner camber 11i and the outer camber 11e of the arm 11. The mid-height line 15 of a given arm 11 extends axially from the trailing edge of the row of stationary blades of the last stage of the high-pressure turbine 6 immediately upstream of the inter-turbine casing 8 to the leading edge 12a of the moving blades 12 of the low-pressure turbine 7 located immediately downstream of the inter-turbine casing 8. The mid-height axial chord 13 then corresponds to the length of the straight line segment connecting points A and B, which correspond to the projections on the axis X of a point A' located at the intersection between the mid-height line 15 and the leading edge 11a of the arm 11 and a point B' located at the intersection between the mid-height line 15 and the trailing edge 11f of the arm 11, respectively.

[0059] Similarly, each splitter blade 12 has a mid-height axial chord length measured by projecting a point located at the intersection between the mid-height line 15 and the leading edge 12a of the splitter blade 12 and a point located at the intersection between the mid-height line 15 and the trailing edge 12f of the splitter blade 12 onto the axis X.

[0060] Finally, the arm-blade distance 16 corresponds to the axial distance between the trailing edge 11f of the arm 11 and the leading edge 13a of the rotor blade 13 immediately downstream of the arm 11, measured at the mid-height of the arm 11, i.e. corresponds to the length of the straight line segment connecting point B (as described above) and point C, wherein point C corresponds to the projection of point C' at the intersection between the mid-height line 15 and the leading edge 13a of the rotor blade 13 onto the axis X. It should be noted here that the arm-blade distance 16 can be measured for any rotor blade 13 of the most upstream stage of the low-pressure turbine 7 (usually referred to as the "first stage" of the low-pressure turbine), as long as the rotor blade 13 is rotationally symmetrical about the axis X, so that, regardless of which rotor blade 13 is selected in this stage, the projection of the point at the intersection between the mid-height line 15 and the leading edge 13a of the rotor blade 13 onto the axis X is the same and coincides with point C.

[0061] From that point on, a downstream TVF plane 17 is defined, which is a plane perpendicular to the axis X at 50% of the arm-to-blade distance 16 , that is to say halfway between points B and C.

[0062] One example of a method for positioning splitter vanes 12 will now be described.

[0063] The method aims at adjusting the azimuth angle of each splitter blade 12, that is to say the angular position about the axis X. Preferably, all groups of splitter blades 12 have the same configuration, that is to say the combination of azimuth angles of each of their splitter blades 12 is the same: in other words, the i-th splitter blade 12 of a group is always located at the same angular distance from the arm 11 preceding it. Thus, in this example, the method seeks to adjust a single given group of splitter blades 12, and the combination of azimuth angles obtained for this group will then be reproduced in the same way for the other groups.

[0064] That is, first a reference position is calculated for each splitter blade 12 in the group under consideration. This reference position corresponds to the position that the splitter blades 12 would have in a classical configuration in which the splitter blades 12 were uniformly distributed around the axis X, that is, a reference configuration in which the deviations between the splitter blades 12 or between the splitter blades 12 and their adjacent arms 11 are always equal. In the present example, using ten arms 11 and three splitter blades 12 per arm 11, it can be calculated that this regular deviation is equal to 360° / (10×(3+1))=9°. Therefore, if the azimuth angle of the arm 11 before the group of splitter blades 12 considered in the clockwise direction is 0°, the reference position of the first splitter blade 12-1 will be 9°, the reference position of the second splitter blade 12-2 will be 18°, and the reference position of the third splitter blade 12-3 will be 27°.

[0065] Numerical simulations or experiments on a test bench are then carried out in a reference configuration to measure the flow velocity through the inter-turbine casing 8 as a function of the azimuthal position in the downstream TVF plane 17, at least along the angular sector separating the two arms 11 constituting the splitter blade set 12 under consideration. Figure 4 The curve 21 shown in the graph of (the graph is represented here in a localized manner, centered on the first blade 12 - 1 of the group considered, since it is the first blade to be positioned).

[0066] On this curve 21, it will be appreciated that the minimum 21a corresponds to the reduction of the flow in the extension of the arm 11, while the minimum 21b corresponds to the reduction of the flow in the extension of the first blade 12-1, which makes it possible to identify them. It should also be noted that the presence of the arm 11 and the blade 12-1 respectively causes velocity peaks 21c and 21d on the inner camber side thereof. In addition to these extremes 21a-21d, which are directly caused by the presence of the arm 11 and the splitter blade 12, it is also noted that there is a local maximum 21e between the arm 11 and the first blade 12-1, followed by a local minimum 21f, and in a similar manner in the clockwise direction, in front of the first blade 12-1, there is a local maximum 21g, followed by a local minimum 21h.

[0067] Then, the velocity distortion Dd between the front and rear of the blade 12-1 constituting the reference distortion is measured between the maximum velocity 21e of the rear portion of the first blade 12-1 in the clockwise direction and the minimum velocity 21h of the front portion of the first blade 12-1 in the clockwise direction.

[0068] Then, the first blade 12-1 is moved forward and / or backward from its reference position, preferably within a range of a maximum deviation of 0.25 times the normal angle, i.e., 0.25×9°=2.25° in this example. Thus, in this example, several positions of the first blade 12-1 between azimuth angles 6.75° and 11.25° can be tested.

[0069] For each test position, numerical simulations or experiments are again performed on the test bench to measure the flow velocity through the inter-turbine casing 8 at least on either side of the first blade 12-1 as a function of the azimuthal position in the downstream TVF plane 17. Then, the following equations are obtained: Figure 4 The curve 22 shown in FIG.

[0070] The extrema 22a-22h are similar to the curve 21 of the reference configuration, but their positions are offset. In particular, it should be noted that the minimum 22b and the maximum 22d are offset forward in the clockwise direction, indicating that the blade 12-1 has moved forward in the clockwise position relative to its reference position.

[0071] In a similar manner to the reference configuration, the velocity distortion Dd' is then measured in an offset configuration between the maximum velocity 22e of the rear of the first blade 12-1 and the minimum velocity 22h of the front of the first blade 12-1. It is then observed that the offset of the blade 12-1 makes it possible to significantly reduce this velocity distortion Dd'.

[0072] The test position can then be maintained so that it is possible to minimize the rate distortion Dd'. Then, once the optimal position of the first blade 12-1 is determined, the same steps can be performed to determine the optimal position of the second blade 12-2 by focusing on the rate distortion between the rear and front of the second blade 12-2. And so on for all the splitter blades 12 in the group.

[0073] Alternatively or additionally, these positionings can also be performed according to another parameter of the flow, in particular the angle of the flow relative to the axis X measured at the downstream TVF plane 17, such as Figure 5 shown.

[0074] therefore, Figure 5 Curve 31 in shows the curve of flow angle in the reference configuration as a function of azimuthal position in the downstream TVF plane 17, while curve 32 shows the curve of flow angle in the offset configuration.

[0075] On these curves, the minimum values ​​31a and 32a make it possible to identify the arm 11, while the minimum values ​​31b, 32b make it possible to identify the first blade 12-1. In the clockwise direction, the flow angular distortion Da, Da' is measured between the maximum values ​​31e, 32e at the rear of the first blade 12-1 and the maximum values ​​31h, 32h at the front of the first blade 12-1. Therefore, it can be noted that the offset of the first blade 12-1 makes it possible to significantly reduce the angular distortion Da' relative to the angular distortion Da in the reference configuration.

[0076] In a variant of an embodiment, in addition to the circumferential offset of at least one splitter blade, the thickness of the splitter blade can also be modified. This modification can involve circumferentially offset blades as well as blades that have not been circumferentially offset.

[0077] In another variation of an embodiment, in addition to the circumferential offset of at least one splitter blade, the stacking pattern of the splitter blades may be modified. Such modification may involve circumferentially offset blades or may involve blades that are not circumferentially offset.

[0078] Although the present invention has been described with reference to specific exemplary embodiments, it is apparent that these examples can be modified and altered without departing from the overall scope of the present invention as defined in the claims. Specifically, the various features of the different illustrated / mentioned embodiments may be combined into further embodiments. Therefore, the description and drawings should be considered in an illustrative rather than a restrictive sense.

[0079] It is also self-evident that all features described with reference to a method can be converted, individually or in combination, into a device and conversely, all features described with reference to a device can be converted, individually or in combination, into a method.

Claims

1. A turbine housing for a turbine, comprising: An inner shield (9), the inner shield being centered on a central axis (X); An outer shield (10) coaxially surrounding the inner shield (9); a plurality of arms (11), each arm (11) extending between the inner shroud (9) and the outer shroud (10), having a leading edge (11a) and a trailing edge (11f), and having a mid-height axial chord length (14); and at least one set of N splitter blades (12) circumferentially positioned between two consecutive arms (11), each splitter blade (12) extending between the inner shroud (9) and the outer shroud (10), having a leading edge (12a) and a trailing edge (12f), and having a mid-height axial chord length that is shorter than a mid-height axial chord length (14) of the arms (11), wherein the two consecutive arms (11) define reference positions for each of the N splitter blades (12), the reference positions being evenly circumferentially spaced between the two consecutive arms (11); and At least one splitter blade (12-1) in the group of N splitter blades (12) is circumferentially offset relative to its reference position.

2. The turbine inter-turbine casing according to claim 1, characterized in that: The arms (11) are evenly distributed around the central axis (X).

3. The turbine inter-turbine casing according to claim 1, characterized in that: At least one arm (11) is hollow and comprises a passage allowing the passage of services of the turbine (1).

4. The turbine casing according to any one of claims 1 to 3, characterized in that: comprising a set of diverter blades (12) located between each of the consecutive arms (11), Each group of flow divider blades (12) includes the same number of flow divider blades (13), and The splitter blades (12) are arranged in the same manner relative to each other in each group of splitter blades (12).

5. The turbine casing according to any one of claims 1 to 4, characterized in that: The profile of at least the downstream portion of the splitter blade (12) is the same as the profile of the downstream portion of the arm (11), and Wherein, the trailing edge (12f) of the splitter blade (12) is circumferentially aligned with the trailing edge (11f) of the arm (11) around the central axis (X).

6. The turbine casing according to any one of claims 1 to 5, characterized in that: All splitter blades (12) in the set of N splitter blades (12) are circumferentially offset relative to their respective reference positions.

7. The turbine housing according to any one of claims 1 to 6, characterized in that: The absolute value of the circumferential offset of the at least one splitter blade (12-1) circumferentially offset relative to its reference position is less than 0.25×Δref, wherein Δref is the angular deviation between two consecutive reference positions.

8. The turbine casing according to any one of claims 1 to 7, characterized in that: At least one splitter blade in the set of N splitter blades (12) has a thickness different from that of the other splitter blades in the set of N splitter blades (12).

9. The turbine inter-turbine casing according to any one of claims 1 to 7, characterized in that: At least one splitter blade of the set of N splitter blades (12) has a different geometry than the other splitter blades of the set of N splitter blades (12), in particular by having a different stacking rule.

10. A turbine assembly comprising: A turbine housing (8) according to any one of the preceding claims, and A turbine (7) extends downstream of the inter-turbine casing (8) and comprises at least one radially extending moving blade (13).

11. The assembly according to claim 10, characterized in that The turbine (7) comprises an impeller carrying a plurality of moving blades (13) which are positioned immediately downstream of the inter-turbine casing (8).

12. A turbine comprising a turbine assembly (7-8) according to claim 10 or 11.

13. A method for positioning a splitter blade in a turbine inter-turbine casing according to any one of claims 1 to 9, comprising the steps of: providing a turbine inter-turbine casing; Positioning splitter blades (12) within the inter-turbine housing at their respective reference positions; evaluating a parameter of flow through the inter-turbine casing (8) on either side of a given splitter blade (12-1) and determining a reference distortion (Dd) of said parameter; moving the given splitter blade (12-1) to one or more azimuthal positions that are circumferentially offset relative to its reference position; as well as For each of these offset azimuth positions: - evaluating parameters of the flow on either side of said given splitter blade (12-1); - Determine the distortion (Dd') of said parameter; as well as - Compare the shifted distortion (Dd') with the reference distortion (Dd); Positioning the splitter vanes at an offset azimuth position within the inter-turbine casing reduces distortion of parameters of the flow.

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