Intermediate turbine housing for a turbomachine, turbomachine assembly, turbomachine and method for positioning a separating guide vane inside an intermediate turbine housing

Description

Technical Field

[0001] This presentation relates generally to an inter-turbine housing for a vane-frame (TVF) turbomachine, which functions as a turbine distributor in such a turbomachine. The present invention relates to an inter-turbine housing for a turbomachine, a turbomachine assembly, a turbomachine itself, and a method for positioning a separator blade within an inter-turbine housing. Previous technique

[0002] In a well-known manner, a turbomachine includes an inter-turbine casing arranged between the high-pressure turbine casing and the low-pressure turbine casing. The inter-turbine casing comprises a fairing with an inner and an outer ring, which together define the flow path between the high-pressure and low-pressure turbines, as well as arms extending radially between the inner and outer rings. Examples of inter-turbine casings are described in US documents 2014 / 328675A1 and 2015 / 110604A1.

[0003] The inter-turbine casing performs several functions: aerodynamic, acting as a stator to deflect the incoming flow from the high-pressure turbine; structural, transferring mechanical forces between the inner and outer shells; and integration, accommodating service lines. The casing can therefore have a multi-profile configuration and, in addition to the arms, include splitter blades (or "splitters") with a shorter chord compared to the arms, which are thicker and have a longer chord. The splitter blades and the downstream section of the arms thus provide the aerodynamic function, while the arms themselves provide the structural and integration functions.

[0004] However, the wakes generated by the inter-turbine casing blades (i.e., the thick arms and the separator blades) are particularly wide and energetic. In particular, the significant differences in profile between the arms and the separator blades result in significant differences in wakes, leading to substantial flow distortions downstream of the inter-turbine casing. These distortions can disrupt the performance of the low-pressure turbine (aerodynamic losses, flow separation), impact its mechanical strength (periodic excitations), or even pose integration problems for the low-pressure turbine (low-pressure turbine size).

[0005] There is therefore a real need to remedy the aforementioned disadvantages, by proposing a solution to improve the aerodynamic efficiency and therefore the performance of the low-pressure turbine in a turbomachine including an inter-turbine casing. Description of the invention

[0006] The present invention relates to an inter-turbine housing for a turbomachine, comprising an inner ferrule, centered on a central axis, an outer ferrule, surrounding the inner ferrule coaxially, a plurality of arms, each arm extending between the inner and outer ferrules, having a leading edge and a trailing edge and having an axial chord at half maximum, and at least one set of N separating blades positioned circumferentially between two successive arms, each separating blade extending between the inner and outer ferrules, having a leading edge and a trailing edge and having an axial chord at half maximum shorter than the axial chord at half maximum of the arms, in which said two successive arms define a reference position for each of said N separating blades, these reference positions being regularly spaced circumferentially between the two successive arms,and wherein at least one separating blade of said set of N separating blades is circumferentially offset from its reference position.

[0007] In other words, in the reference configuration, the azimuth A i of the reference position of the separating blade of said set of N separating blades, that is to say its angular position around the central axis, can be written as follows A i = A B1 + (A B2 -A B1 ) / (N+1), with A B1 the azimuth of the first arm and A B2 the azimuth of the second arm delimiting said set of N separating blades.

[0008] Thus, in such a configuration according to the invention, unlike the conventional configuration usually found in rotating machines, the separating blades are not all arranged regularly between the arms.

[0009] Indeed, the inventors observed that the reference configuration, in which the arms and separating blades are regularly spaced around the central axis, generated significant distortions in the flow rate and direction of the flow passing through the inter-turbine casing. Conversely, the inventors determined that offsetting all or part of the separating blades from their commonly accepted reference positions reduced flow distortions, thus increasing the performance of the downstream turbine.

[0010] Thus, the invention is the result of technological research aimed at significantly improving the performance of turbomachinery and, in this sense, contributes to reducing the environmental impact of the aeronautical sector.

[0011] In some embodiments, the plurality of arms includes between 4 and 20 arms.

[0012] In some embodiments, the arms are distributed regularly around the central axis. Their distribution is therefore axisymmetric.

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

[0014] In some embodiments, at least one arm is hollow, said at least one arm comprising a passage allowing the passage of a turbomachine service.

[0015] In some embodiments, said set of N separating vanes comprises between 1 and 4 separating vanes.

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

[0017] In some embodiments, each set of separating blades comprises the same number of separating blades.

[0018] In some embodiments, the separating blades are arranged in the same way relative to each other in each set of separating blades. Thus, the configuration of each set of separating blades, that is to say the combination of the respective arrangements of each of their blades, constitutes the same pattern which is repeated identically between arms.

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

[0020] In some embodiments, the axial chord at mid-height of the separating blades is at least 2 times shorter, preferably at least 3 times shorter, than the axial chord at mid-height of the arms.

[0021] In some embodiments, the maximum thickness of the separating blades is less than the maximum thickness of the arms.

[0022] In some embodiments, the maximum thickness of the separating blades is at least 2 times shorter, preferably at least 3 times shorter, than the maximum thickness of the arms.

[0023] In some embodiments, the profile of at least a downstream portion of the separation blades is identical to the profile of a downstream portion of the arms. The aerodynamic behavior of the arms and separation blades is thus analogous, at least near their trailing edges, which reduces flow distortions.

[0024] In some embodiments, the trailing edges of the separating blades are circumferentially aligned around the central axis with the trailing edges of the arms.

[0025] In some embodiments, the leading edges of the separating blades are arranged further downstream than the leading edges of the arms.

[0026] In some embodiments, at least one separating blade of the set of N separating blades adjacent to an arm is offset conferentially with respect to its respective reference position. This is preferably the case for both separating blades of the set adjacent to an arm. This helps to reduce distortions caused by the difference in profile of the arms.

[0027] In certain embodiments, all the separating blades of said set of N separating blades are circumferentially offset from their respective reference positions.

[0028] In some embodiments, the circumferential offset of at least one separating blade that is circumferentially offset from its reference position is less than 0.25 x Δref, where Δref is the angular distance between two consecutive reference positions. Preferably, no separating blade has a circumferential offset from its reference position that exceeds this absolute value. Indeed, the inventors have determined that the optimal offset range lies within this range.

[0029] In certain embodiments, at least one separating blade of said set of N separating blades has a different thickness from the other separating blades of said set of N separating blades. Consequently, in such a case, the trailing edge stacking of the cross-sections of the blade in question does not coincide with the trailing edge stacking of the cross-sections of the arm.

[0030] In certain embodiments, at least one separating blade of said set of N separating blades has a different geometry, in particular by exhibiting a different stacking pattern, from the other separating blades of said set of N separating blades. Similarly, in such a case, the trailing edge stacking pattern of the cross-sections of the blade in question does not coincide with the trailing edge stacking pattern of the cross-sections of the arm.

[0031] The present invention also relates to a turbomachine assembly, comprising an inter-turbine casing according to any of the preceding embodiments, and a turbine extending downstream of the inter-turbine casing and comprising at least one movable blade extending radially.

[0032] The present invention also relates to a turbomachine, comprising a turbomachine assembly according to any one of the preceding embodiments.

[0033] The present invention also relates to a method of positioning a separator blade within an inter-turbine housing according to any one of the preceding embodiments, comprising the following steps: provide an inter-turbine casing, positioning separator blades within the inter-turbine casing in their respective reference positions; evaluate a flow parameter passing through the inter-turbine casing on either side of a given separator blade and determine a reference distortion of this parameter; move said given separator blade into one or more azimuthal positions circumferentially offset from its reference position; and for each of these offset azimuthal positions: evaluate said flow parameter on either side of the given separator blade (12-1), determine the distortion (Dd') of this parameter, and compare the distortion after displacement (Dd') with the reference distortion (Dd), position the separator blade within the inter-turbine casing at an offset azimuthal position that reduces the distortion of said flow parameter.

[0034] It is understood here that the positioning, displacement, and parameter evaluation steps can be carried out experimentally or numerically using a numerical simulation. A staggered position is then selected for the given separator blade, which reduces, or even minimizes, the distortion of the flow parameter.

[0035] In some embodiments, the flow parameter is evaluated as a function of the azimuthal position in a downstream radial plane.

[0036] In some embodiments, the step of evaluating the flow parameter after displacement is carried out for several different offset positions of the given separating blade within an exploration range.

[0037] In some embodiments, the exploration range has an amplitude greater than 0.1 x Δref and less than 0.25 x Δref, where Δref is the angular deviation between two consecutive reference positions.

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

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

[0040] In this presentation, the terms "longitudinal", "transverse", "lower", "upper" and their derivatives are defined with respect to the main direction of the blades; the terms "axial", "radial", "tangential", "inner", "outer" and their derivatives are defined with respect to the central axis of the inter-turbine casing, i.e. the main axis of the turbomachine; "axial plane" means a plane passing through the main axis of the turbomachine and "radial plane" means a plane perpendicular to this main axis; the terms "upstream" and "downstream" are defined with respect to the airflow in the turbomachine; finally, the terms "front" and "rear" are understood in the circumferential direction when progressing in a clockwise direction.

[0041] The aforementioned features and advantages, as well as others, will become apparent upon reading the detailed description that follows, along with examples of the inter-turbine housing and the proposed process. This detailed description refers to the attached drawings. Brief description of the drawings

[0042] The attached drawings are schematic and are primarily intended to illustrate the principles of the invention.

[0043] In these drawings, from one figure to another, identical elements (or parts of elements) are identified by the same reference symbols. [ Fig. 1 ] There figure 1 is an axial cross-sectional view of a turbomachine according to the invention. Fig. 2 ] There figure 2 is a cross-sectional view of a turbomachine assembly including an example of an inter-turbine casing and a turbine. Fig. 3 ] There figure 3 is a partial perspective view of the overall example turbomachine of the figure 2 . [ Fig. 4 ] There figure 4 is a graph representing the flow rate as a function of the azimuthal position for a reference configuration and an offset configuration. Fig. 5 ] There figure 5 is a graph representing the flow angle as a function of the azimuthal position for the reference configuration and the offset configuration of the figure 4 . Description of the implementation methods

[0044] To illustrate the invention more concretely, an example of an inter-turbine housing is described in detail below, with reference to the accompanying drawings. It should be noted that the invention is not limited to this example.

[0045] A turbofan 1 (typically, an aircraft turbofan 1) generally comprises, from upstream to downstream in the direction of gas flow, a fan 2, an annular primary flow channel I and an annular secondary flow channel II. The air mass drawn in by the fan 2 is thus divided into a primary flow, which circulates in the primary flow channel I, and a secondary flow, which is concentric with the primary flow and circulates in the secondary flow channel II.

[0046] The primary flow stream I passes through a primary body comprising one or more stages of compressors, for example a low pressure compressor 3 and a high pressure compressor 4, a combustion chamber 5, one or more stages of turbines, for example a high pressure turbine 6 and a low pressure turbine 7 separated by an inter-turbine casing 8, and a gas exhaust nozzle.

[0047] In this application, upstream and downstream are defined with respect to the normal flow direction of the gases in the turbomachine 1. Furthermore, the axis of rotation of the rotor of the low-pressure turbine 7, which coincides with the extension axis of the turbomachine 1, is called axis X. An axial direction corresponds to the direction of axis X; a radial direction is a direction perpendicular to and passing through axis X. A circumferential direction corresponds to a direction perpendicular to axis X but not passing through it.

[0048] The inter-turbine casing 8 comprises an inner ring 9 and an outer ring 10 substantially coaxial with the X-axis, and a fixed blade comprising a plurality of arms 11 forming a ring. The arms 11 extend from the inner ring 9 to the outer ring 10 and may be substantially radial with respect to the X-axis. Each arm 11 includes a structural portion, configured to transmit mechanical forces between the inner ring 9 and the outer ring 10, which is housed in an aerodynamically shaped wall.

[0049] 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, which is located immediately downstream of the inter-turbine casing 8.

[0050] The inter-turbine casing 8 may include between four and twenty arms 11. In this example, the inter-turbine casing 8 includes ten arms 11. Preferably, these arms 11 are regularly spaced around the X-axis. The inter-turbine casing 8 also includes a plurality of separator blades 12 positioned circumferentially between the arms 11: a set of one or more separator blades 12 is thus provided between each arm 11. It should be noted that, conventionally, the chord of each separator blade 12 is shorter than the chord of each arm 11. The trailing edge 12f of each separator blade 12 is circumferentially aligned with the trailing edge 11f of each arm 11; Consequently, the leading edges 11a of the arms 11 are positioned further upstream than the leading edges 12a of the separating blades 12. Moreover, preferably, the downstream part of the arms 11 has a profile corresponding to at least one downstream part of the separating blades 12.

[0051] The inter-turbine housing 8 may include between one and four separator blades 12 between successive arms 11. Preferably, each set of separator blades 12 comprises the same number of blades 12. In the present example, three separator blades 12 are thus provided between each arm 11.

[0052] The low-pressure turbine 7 comprises, in a manner known per se, a plurality of turbine stages, each 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 case of a turbomachine whose fan 2 is driven via a reduction mechanism. As the low-pressure turbine 7 is conventional, it will not be described in further detail here.

[0053] Each arm 11 has an axial chord at mid-height 14. The axial chord at mid-height 14 of a given arm 11 is defined from a mid-height line 15, which corresponds to the (fictitious) line included in a plane perpendicular to the X axis and which includes all the points located midway between the inner ferrule 9 and the outer ferrule 10 and midway between the intrados 11i and the extrados 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 fixed 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 blade 12 of the low-pressure turbine 7 located immediately downstream of the inter-turbine casing 8.The axial chord at mid-height 13 then corresponds to the length of the straight segment connecting points A and B, which correspond respectively to the projection onto the X axis of point A' located at the intersection between the mid-height line 15 and the leading edge 11a of arm 11, and of point B' located at the intersection between the mid-height line 15 and the trailing edge 11f of arm 11.

[0054] Similarly, each separating blade 12 has an axial chord at mid-height measured by projecting onto the X axis the points located at the intersection between the mid-height line 15 and the leading edge 12a of the separating blade 12, and at the intersection between the mid-height line 15 and the trailing edge 12f of the separating blade 12.

[0055] Finally, the arm-blade distance 16 corresponds to the axial distance, measured at mid-height of the arm 11, between the trailing edge 11f of the arm 11 and the leading edge 13a of a movable blade 13 immediately downstream of the arm 11, that is to say the length of the straight segment connecting points B (defined above) and C, where point C corresponds to the projection onto the X axis of point C' located at the intersection between the mid-height line 15 and the leading edge 13a of the movable blade 13.It should be noted here that the arm-blade distance 16 can be measured for any moving blade 13 of the upstream stage of the low pressure turbine 7 (generally designated as the "first stage" of the low pressure turbine), insofar as the moving blades 13 are symmetrical about the X axis so that, whatever moving blade 13 is selected in this stage, the projection onto the X axis of the point at the intersection between the mid-height line 15 and the leading edge 13a of the moving blade 13 is identical and coincides with the point C.

[0056] Therefore, we define the downstream plane TVF 17, which is the plane perpendicular to the X axis at 50% of the arm-blade distance 16, that is to say halfway between points B and C.

[0057] An example of a method for positioning the separating blades 12 will now be described.

[0058] This process aims to adjust the azimuth, that is, the angular position around the X-axis, of each separating blade 12. Preferably, all sets of separating blades 12 have the same configuration, that is, the same combination of azimuths for each of their separating blades 12: in other words, the separating blade 12 of a set is always located at the same angular distance from the preceding arm 11. Therefore, in this example, the process focuses on adjusting the azimuth of the separating blades 12 of a single given set, and then the azimuth combination obtained for this set will be reproduced identically for the other sets.

[0059] Having specified this, a reference position is first calculated for each separating blade 12 in the set under consideration. This reference position corresponds to the position that the separating blade 12 would have in the classic configuration of equal distribution around the X-axis, that is to say, the reference configuration in which the gap between the separating blades 12 or between a separating blade 12 and its adjacent arm 11 is always equal. In the present example, with ten arms 11 and three separating blades 12 per arm 11, we can calculate that this regular gap is equal to 360° / (10x(3+1)) = 9°. Therefore, if the arm 11 preceding the set of separating blades 12 considered in the clockwise direction has the azimuth 0°, the reference position of the 1st separating blade 12-1 will be 9°, the reference position of the 2nd separating blade 12-2 will be 18°, and the reference position of the 3rd separating blade 12-3 will be 27°.

[0060] A numerical simulation, or a test bench experiment, is then carried out in the reference configuration to measure the flow rate 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 framing the set of separation blades 12 under consideration. A curve 21 is then obtained, as shown on the graph of the figure 4 (this graph is represented here in a partial way, centered on the first 12-1 dawn of the game considered since it is the first dawn that we will try to position).

[0061] On curve 21, it is important to understand that the minimum 21a corresponds to the flow reduction along the extension of arm 11, while the minimum 21b corresponds to the flow reduction along the extension of the first blade 12-1, which allows for their identification. It is also noted that the presence of arm 11 and blade 12-1 causes flow peaks 21c and 21d respectively on their undersides. In addition to these extrema 21a-21d directly caused by the presence of arms 11 and the separating blades 12, there is a local maximum 21e followed by a local minimum 21f between arm 11 and the first blade 12-1, as well as, similarly, a local maximum 21g followed by a local minimum 21h ahead of the first blade 12-1 in a clockwise direction.

[0062] The flow distortion Dd between the front and rear of the blade 12-1, constituting a reference distortion, is then measured between the maximum flow 21e behind the first blade 12-1 in the clockwise direction and the minimum flow 21h in front of the first blade 12-1 in the clockwise direction.

[0063] The first blade 12-1 is then moved forward and / or backward from its reference position, preferably within a range deviating by a maximum of 0.25 times the normal angular deviation, i.e., 0.25 x 9° = 2.25° in this example. Thus, in this example, several positions can be tested for the first blade 12-1 between azimuths of 6.75° and 11.25°.

[0064] For each tested position, a numerical simulation or a test bench experiment is again conducted to measure the flow rate through the inter-turbine casing 8 as a function of the azimuthal position in the downstream plane TVF 17, at least on either side of the first blade 12-1. This yields curve 22 as shown on the graph of the figure 4 .

[0065] We then find extrema 22a-22h analogous to those of curve 21 of the reference configuration, but with shifted positions. In particular, we note that the minimum 22b and the maximum 22d are shifted forward in a clockwise direction, which reveals that blade 12-1 has been moved forward in a clockwise direction relative to its reference position.

[0066] Similar to what was done for the reference configuration, the flow distortion Dd' is then measured in this offset configuration between the maximum flow 22e behind the first blade 12-1 and the minimum flow 22h ahead of the first blade 12-1. It is then observed that the offset of the blade 12-1 has significantly reduced this flow distortion Dd'.

[0067] It is then possible to retain the tested position that minimizes the flow distortion Dd'. Next, once the optimal position of the first blade 12-1 has been determined, the same steps can be performed to determine the optimal position of the second blade 12-2 by considering the flow distortion between the rear and front of the second blade 12-2. And so on for all the separating blades 12 in the set.

[0068] Alternatively, or in addition, it is also possible to perform these positionings based on another flow parameter, and in particular the flow angle relative to the X-axis as measured at the downstream plane TVF 17, as shown on the figure 5 .

[0069] Thus, curve 31 of the figure 5 represents the flow angle curve as a function of the azimuthal position in the downstream plane TVF 17 in the reference configuration, while curve 32 represents the flow angle curve in the offset configuration.

[0070] On these curves, minima 31a and 32a allow us to locate arm 11, while minima 31b and 32b allow us to locate the first blade 12-1. The flow angle distortion Da, Da' is measured between the maximum 31e, 32e aft of the first blade 12-1 and the maximum 31h, 32h ahead of the first blade 12-1, in a clockwise direction. We can thus observe that the offset of the first blade 12-1 has significantly reduced the angle distortion Da' compared to the angle distortion Da in the reference configuration.

[0071] In one embodiment, in addition to a circumferential offset of at least one separator blade, it is also possible to modify the thickness of a separator blade. This modification can apply to both a circumferentially offset blade and one that has not been circumferentially offset.

[0072] In another embodiment, in addition to a circumferential offset of at least one separator blade, it is also possible to modify the stacking law of a separator blade. This modification can apply to either a circumferentially offset blade or a blade that has not been circumferentially offset.

[0073] Although the present invention has been described with reference to specific embodiments, it is evident that modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various embodiments illustrated / mentioned can be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

[0074] It is also evident that all the characteristics described with reference to a process are transposable, alone or in combination, to a device, and conversely, all the characteristics described with reference to a device are transposable, alone or in combination, to a process.

Claims

1. An inter-turbine casing for a turbomachine, comprising: an inner shroud (9), centered on a central axis (X), an outer shroud (10), coaxially surrounding the inner shroud (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 (14), and at least one set of N splitter blades (12) positioned circumferentially between two successive 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 shorter than the mid-height axial chord (14) of the arms (11), wherein said two successive arms (11) define a reference position for each of said N splitter blades (12), these reference positions being evenly spaced circumferentially between the two successive arms (11), and wherein at least one splitter blade (12-1) of said set of N splitter blades (12) is circumferentially offset relative to its reference position.

2. The inter-turbine casing according to claim 1, wherein the arms (11) are evenly distributed about the central axis (X).

3. The inter-turbine casing according to claim 1, wherein at least one arm (11) is hollow, said at least one arm (11) comprising a passage allowing the passage of a service of the turbomachine (1).

4. The inter-turbine casing according to any one of claims 1 to 3, comprising a set of splitter blades (12) between each successive arm (11), wherein each set of splitter blades (12) comprises the same number of splitter blades (12), and wherein the splitter blades (12) are disposed in the same manner, relative to each other, in each set of splitter blades (12).

5. The inter-turbine casing according to any one of claims 1 to 4, wherein the profile of at least a downstream portion of the splitter blades (12) is identical to the profile of a downstream portion of the arms (11), and wherein the trailing edges (12f) of the splitter blades (12) are circumferentially aligned about the central axis (X) with the trailing edges (11f) of the arms (11).

6. The inter-turbine casing according to any one of claims 1 to 5, wherein all the splitter blades (12) of said set of N splitter blades (12) are circumferentially offset relative to their respective reference positions.

7. The inter-turbine casing according to any one of claims 1 to 6, wherein the circumferential offset of said at least one splitter blade (12-1) which is circumferentially offset relative to its reference position is smaller in absolute value than 0.25 x Δref, where Δref is the angular deviation between two consecutive reference positions.

8. The inter-turbine casing according to any one of claims 1 to 7, wherein at least one splitter blade of said set of N splitter blades (12) has a thickness different from the other splitter blades of said set of N splitter blades (12).

9. The inter-turbine casing according to any one of claims 1 to 7, wherein at least one splitter blade of said set of N splitter blades (12) has a different geometry, in particular by having a different stacking law, from the other splitter blades of said set of N splitter blades (12).

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

11. The assembly according to claim 10, wherein the turbine (7) comprises an impeller, carrying a plurality of moving blades (13), located immediately downstream of the inter-turbine casing (8).

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

13. A method for positioning a splitter blade within an inter-turbine casing according to any one of claims 1 to 9, comprising the following steps: providing an inter-turbine casing; positioning splitter blades (12) within the inter-turbine casing in their respective reference positions; evaluating a parameter of the flow passing through the inter-turbine casing (8) on either side of a given splitter blade (12-1) and determining a reference distortion (Dd) of this parameter; moving said given splitter blade (12-1) into one or more azimuthal positions circumferentially offset relative to its reference position; and for each of these offset azimuthal positions: - evaluating said parameter of the flow on either side of the given splitter blade (12-1), - determining the distortion (Dd') of this parameter, and - comparing the distortion after displacement (Dd') with the reference distortion (Dd), positioning the splitter blade within the inter-turbine casing at an offset azimuthal position which reduces the distortion of said parameter of the flow.