FEEDWHEEL FOR A TURBOPUMP AND TURBOPUMP

Description

FIELD OF INVENTION

[0001] The present invention relates to the field of inductors for space turbopumps, and a turbopump equipped with such an inductor. STATE OF PRIOR ART

[0002] An inductor is a rotor component of a turbopump used to draw fluid into the pump upstream of the impeller compression stage(s). A turbopump with such an inductor is described, for example, in patent application FR2765639. FR 2 804 730 A1 discloses another example of a turbopump inductor.

[0003] The operation of space turbopump inductors typically results in an unstable operating range characterized by fluctuations in inductor force due to cavitation. These fluctuations can disrupt the proper functioning of the shaft line (rotor dynamics) or increase wear on the inductor blades.

[0004] One solution to limit cavitation instabilities within the inductor is to create a bevel on the leading edge of the inductor blades. This bevel helps stabilize the area where cavitation pockets form on the upper surface, where the pressure drop leads to the formation of bubbles.

[0005] However, this bevel does not stabilize the extent of these pockets along the fluid flow direction, leaving a degree of freedom for the flow. An instability therefore remains, created by the oscillations of the cavitation pockets, generating a hydraulic imbalance on the turbopump.

[0006] Therefore, there is a need for a turbopump inductor to stabilize the cavitation pockets that appear at the inductor blades. PRESENTATION OF THE INVENTION

[0007] The present description relates to an inductor for a turbopump as defined in claim 1, comprising a plurality of blades arranged between an inner casing and an outer casing, each blade having an intrados and an extrados, the extrados of at least one blade having a recess, the recess extending substantially from the leading edge of the blade to a walking surface arranged on the extrados.

[0008] The term "extrados" refers to the surface of the blade located on the side where the fluid enters the injector (the upper surface as the fluid flows through the injector from top to bottom). The recess corresponds to a specific area of ​​the extrados. The presence of a recess on the blade's extrados is characterized by the fact that, instead of having a traditional profile with a normally non-concave cross-section, the blade's extrados presents, in a cross-section perpendicular to the blade's leading edge, a thinned, concave, or essentially concave section, formed in a depression relative to traditional profiles, and delimited downstream by a surface called the tread. In other words, the recess involves removing a layer of material from a predetermined area of ​​the blade's surface, starting from a traditional blade profile.Therefore, the extrados has a walking surface, corresponding to the slope existing between the area of ​​the extrados with the excavation, and the area of ​​the extrados without the excavation.

[0009] The recess thus implies an abrupt change in the profile of the upper surface. More precisely, the step surface resembles a stair step, characterized by a nearly vertical wall joining two nearly horizontal surfaces at different heights. By comparison, the chamfering on the leading edge of some inductor blades, designed to limit cavitation instabilities, does not constitute a recess, nor a step surface. Indeed, in this case, the blade thickness changes gradually from the tip of the chamfer to the edge corresponding to the tangent between the chamfered surface and the rest of the blade. The change in blade thickness is therefore not discontinuous, but gradual. Conversely, the presence of a recess implies a discontinuity in the blade thickness, resulting in an abrupt change in its thickness.

[0010] The said recess extends substantially from the leading edge of the blade, corresponding to the upstream end of the blade, to the walking surface. The upstream or downstream end of the blade is understood to be the ends in a circumferential direction and along the normal direction of fluid flow in the inductor.

[0011] The position of the tread surface on the upper surface of the blade is determined, for example, by preliminary experimental tests carried out without recesses, allowing the study of the shape of the cavitation pockets forming on the upper surface of the blade. Preferably, the overall shape of the recess, and therefore the position of the tread surface, in a view along an axis of rotation of the inductor, corresponds approximately to the shape of the cavitation pockets, in this same view, forming on the upper surface. By position of the tread surface, we mean its position on the upper surface of the blade, its shape, and its radius of curvature in a view along the axis of rotation of the inductor.

[0012] Thus, when a cavitation pocket forms on the upper surface of a blade according to the invention, advantageously, the pocket, in the circumferential direction of the blade, is delimited upstream by the leading edge and downstream by the tread surface. The latter thus limits or even eliminates the oscillatory movements of the cavitation pockets, thereby stabilizing the dynamics of the inductor, thereby reducing wear on the inductor blades and the hydraulic imbalances acting on the turbopump shaft.

[0013] The leading edge of said at least one blade has a beveled surface, the recess extending from a downstream end of the beveled surface to the walking surface on the extrados.

[0014] The beveled surface, which can be produced by machining, is a surface that is formed so that, in a cross-sectional view of the blade along a cutting plane parallel to the axis of rotation of the inductor, the leading edge locally has a straight segment.

[0015] This beveled shape of the surface, and therefore of the blade's leading edge, helps to contain the cavitation pocket that forms at said leading edge. The length of the cavitation pocket is thus defined between this beveled surface and the walking surface.

[0016] In some embodiments, the recess extends radially over all or part of the leading edge of said at least one blade.

[0017] In some embodiments, the recess extends radially substantially from a radially internal limit of said at least one blade on the side of a central axis of the inductor, in the vicinity of the leading edge, to a radially external end of said at least one blade.

[0018] In some embodiments, the walking surface forms, in a view along an axis of the inductor, an arc of a circle with a concavity directed towards the center of the inductor.

[0019] In some embodiments, the walking surface, in a view along an axis of the inductor, has a variable radius of curvature from a radially internal limit of the blade on the side of a central axis of the inductor to a radially external end of the blade.

[0020] According to the claimed invention, the excavation is delimited by a bottom surface and the walking surface.

[0021] The bottom surface corresponds to the surface of the upper surface on which the excavation was carried out, and its shape, in a view along the axis of rotation of the inductor, corresponds to the shape of the cavitation pocket forming on the upper surface when the inductor is in operation. The bottom surface also has a relatively small curvature.

[0022] In some embodiments, the bottom surface and the walking surface are connected by a fillet joint.

[0023] This helps to limit the stresses at the junction between the base surface and the running surface when the inductor is in operation.

[0024] According to the claimed invention, the extrados has a downstream surface downstream of the walking surface, and the walking surface and the downstream surface are connected by a sharp edge.

[0025] Similar to the beveled surface on the leading edge, this sharp edge helps to define the downstream limit of the cavitation pocket, preventing it from extending beyond the walking surface. Consequently, since the upper surface of the blade has an upstream attachment zone on the leading edge and a downstream attachment zone at the walking surface, fluctuations in the cavitation pocket forming on the upper surface are limited, or even eliminated, thus reducing dynamic instabilities during inductor operation and consequently reducing wear on the inductor blades.

[0026] In some embodiments, the thickness of the blade at the bottom surface, halfway between the leading edge and the walking surface, in a view along a cutting plane parallel to an axis of the inductor, has a value between 50 and 80% of the maximum thickness of the blade, preferably between 60 and 70%, preferably still between 65 and 67%.

[0027] These blade thickness values ​​at the recess allow the mechanical integrity of the blade to be maintained during the operation of the inductor.

[0028] This presentation also concerns a turbopump including the inductor defined previously. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The invention and its advantages will be better understood upon reading the detailed description below of various embodiments of the invention, given by way of non-limiting examples. This description refers to the accompanying figure pages, on which: there figure 1A represents a schematic cross-sectional view of a blade leading edge without a recess, and the figure 1B represents a schematic cross-sectional view of a blade leading edge with a recess. figure 2A represents a perspective view of a turbopump inductor according to the present invention, and the figure 2B represents the inductor of the figure 2A , according to the enlarged view IIB. the figure 3 represents a schematic view of the inductor of the present invention along its axis of rotation. figure 4 represents a cross-sectional view of the inductor of the present invention along line IV-IV of the figure 3 . there figure 5 represents a cross-sectional view of a turbopump including the inductor of the figure 2A . DETAILED DESCRIPTION OF ACHIEVED EXAMPLES

[0030] In the following description, upstream and downstream are understood to mean, according to the direction of rotation of the inductor, the leading edge of a blade being located upstream, and the trailing edge downstream.

[0031] There figure 1A This represents a schematic cross-sectional view of a portion of a blade 10 comprising a leading edge 22 and an upper surface 20, without a recess. The blade 10 is a blade of the inductor 1 shown in the various figures. The leading edge 22 has a chamfered surface 222, obtained, for example, by machining the leading edge 22, so as to obtain a blade whose upstream end 221 has a salient angle.

[0032] When the blade 10 is in motion, a cavitation pocket 30 can form at the leading edge 22. This cavitation pocket 30 attaches to the salient angle existing at the upstream edge 223 between the beveled surface 222 and the upper surface 20 of the blade 10. This cavitation pocket then extends over a portion of the upper surface 20. When the blade 10 is in motion, the downstream end of this cavitation pocket 30 tends to fluctuate during the operation of the turbopump (arrow on the figure 1A ).

[0033] There figure 1B represents a schematic cross-sectional view of the portion of blade 10, this time showing a recess. The recess is achieved by removing material from the upper surface 20, for example by machining, over a length, in the upstream-downstream direction, corresponding approximately to the length of the cavitation pocket forming on the upper surface in the absence of a recess ( figure 1A ).

[0034] Due to this recess, the upper surface 20 of the blade 10 is divided into four surfaces: the beveled surface 222, a bottom surface 24 corresponding to the area of ​​the upper surface containing the recess, a tread surface 26, and a down-surface 28, corresponding to the area of ​​the upper surface without the recess. The tread surface 26 forms the junction between the bottom surface 24 (hatching on the figure 3 ) and the downstream surface 28, and allows to compensate for the variation in thickness of the blade 10 in this area, caused by the removal of material.

[0035] Thus, when the cavitation pocket 30 forms, its upstream end is fixed on the upstream edge 223, and its downstream end is fixed on the salient angle existing at the level of the edge 261 between the walking surface 26 and the downstream surface 28. Consequently, when the blade 10 is in motion, the cavitation pocket 30 is limited in its movements, its downstream end no longer being able to oscillate.

[0036] There figure 3 This represents a schematic view of an inductor 1 along its axis of rotation, showing a recess on each of its blades. The recess is delimited by the bottom surface 24, by the upstream edge 223 and by the downstream edge 261.

[0037] The upstream edge 223, corresponding to the downstream end of the beveled surface 22, presents, according to the view of the figure 3 , a curved shape substantially parallel to the upstream end 221 of the leading edge, and extends between a radially internal limit Li of the blade on the side of the central axis of the inductor, and a radially external limit Le of the blade.

[0038] The downstream ridge 261 also presents, according to the view of the figure 4 The blade has a curved shape and extends between a radially internal boundary Li of the blade on the side of the inductor's central axis and a radially external boundary Le' of the blade. In this example, the downstream edge 261 has the shape of a circular arc whose concavity is directed downstream. Furthermore, in this example, the radially internal boundary Li of edges 223 and 261 coincide. Conversely, the radially external boundary Le' of the downstream edge 261 is located further downstream than the radially external boundary Le of the upstream edge 223.

[0039] The shape of the recess thus obtained corresponds to the shape of the cavitation pocket 30 forming on each of the blades 10 of the inductor, so that this pocket 30 is limited in its movements by the bottom surface 24 and the edges 223 and 261 during the operation of the inductor.

[0040] In this example, the thickness e of the blade 10 at the level of the recess represents approximately between 65% and 70% of the maximum thickness Emax of the blade 10 at the downstream surface 28. Since the thickness of the blade 10 is not constant, the section considered to evaluate the thickness e corresponds here to the mid-distance between the upstream edge 223 and the downstream edge 261.

[0041] Preferably, the thickness e of the blade 10 is greater than 60% of the maximum thickness E, regardless of the section considered, so as to maintain the mechanical integrity of the blade 10. Furthermore, the bottom surface 24 and the tread surface 26 are joined by a fillet, clearly visible on the figure 2B This helps to limit the stresses at this junction when inductor 1 is in operation.

[0042] There figure 2A Figure 1 represents a perspective view of a turbopump inductor according to the present invention, comprising a recess on each of its blades 10, each blade having a bottom surface 24, a downstream surface 28, a running surface 26, and a chamfered surface 22. When the inductor 1 is integrated into a turbopump, the presence of the recesses on the blades limits fluctuations in the lengths of cavitation pockets, thereby stabilizing the dynamics of the turbopump shaft by limiting hydraulic imbalances caused by unsteady cavitation regimes. This increases the engine's service life without reducing the inductor's efficiency.

[0043] Alternatively, the shape of the bottom surface 24 described above may be different, depending on the shape of the cavitation pockets forming on the upper surface. For example, the walking surface 26, in a view along the axis of rotation of the inductor, may have a variable radius of curvature, for example increasing, in a radial direction, between a radially internal limit of the blade 10 on the side of a central axis of the inductor, and a radially external end of the blade 10.

[0044] There figure 5Figure 100 represents a cross-sectional view of a turbopump 100, including the inductor 1 of this presentation, intended primarily, but not exclusively, for pumping fluids such as liquefied gas. The terms "axial" and "radial" are defined with respect to the axis of rotation A of the turbopump 100, while the terms "upstream" and "downstream" are defined with respect to the direction of fluid intake. Considered along the intake direction, schematically indicated here by arrows, the turbopump 100 comprises successively a suction stage 12, a centrifugal impeller 14, and an annular conduit 16 for discharging the intake fluid. The suction stage 12 includes the rotary inductor 1 equipped with a hub 20 driven in rotation by a rotation shaft 110 of the turbopump 100, the rotation shaft 110 being driven by an electric motor 112 located downstream of the centrifugal wheel 14. The rotation shaft 110 also drives the centrifugal wheel 14 in rotation.

[0045] 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. For example, edge 223 may not be a sharp edge, but a fictitious edge, in the form of a rounded surface such as a fillet. In particular, individual features of the various embodiments illustrated / mentioned may be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

Claims

1. An inducer (1) for a turbopump including a plurality of blades (10) disposed between an inner casing and an outer casing, each blade (10) having a pressure side, a suction side (20), and a leading edge (22) including a beveled surface (222), the suction side (20) of at least one blade (10) having a recess, characterized in that the recess extends from a downstream end (223) of the beveled surface (222) of the leading edge (22) of the blade (10) to a step surface (26) arranged on the suction side (20), the step surface (26) being a substantially vertical wall joining a bottom surface (24) of the recess and a downstream surface (28) of the suction side (20) downstream of the step surface (26), the bottom surface (24) and the downstream surface (28) being two substantially horizontal surfaces, arranged at different heights from one another, the step surface (26) and the downstream surface (28) being connected by a sharp edge (261).

2. The inducer (1) according to claim 1, wherein the recess extends radially substantially from a radially inner limit of said at least one blade (10) on the side of a central axis of the inducer (1), proximate to the leading edge (22), to a radially outer end of said at least one blade (10).

3. The inducer (1) according to claim 1 or 2, wherein the step surface (26) forms, in a view along an axis of the inducer, an arc of circle with a concavity directed toward the center of the inducer (1).

4. The inducer (1) according to any one of the preceding claims, wherein the recess is delimited by the bottom surface (24) and the step surface (26), the bottom surface (24) and the step surface (26) being connected by a fillet.

5. The inducer (1) according to any one of the preceding claims, wherein a radially inner limit (Li) of the sharp edge (261) coincides with a radially inner limit (Li) of the downstream end (223) of the beveled surface (222), and a radially outer limit (Le') of the sharp edge (261) is located further downstream than a radially outer limit (Le) of the downstream end (223) of the beveled surface (222).

6. A turbopump (100) comprising the inducer (1) according to any one of the preceding claims.