EP3507498A1

EP3507498A1 - Turbopump inducer and turbopump

Info

Publication number: EP3507498A1
Application number: EP17771802.0A
Authority: EP
Inventors: Thomas WATIOTIENNE; Nicolas LE MERCIER
Original assignee: ArianeGroup SAS
Current assignee: ArianeGroup SAS
Priority date: 2016-09-01
Filing date: 2017-08-30
Publication date: 2019-07-10
Also published as: FR3055373B1; WO2018042123A1; FR3055373A1

Abstract

A turbopump inducer for stabilising the cavitation pockets occurring at the blades of the inducer, the inducer having a plurality of blades (10) disposed between an inner housing and an outer housing, each blade (10) having a lower surface and an upper surface (20), the upper surface (20) of at least one blade (10) having a cut-out portion extending substantially from the leading edge (22) of the blade (10) to a step surface (26) provided on the upper surface (20).

Description

Turbopump and turbopump inductor

FIELD OF THE INVENTION

The present invention relates to the field of inductors of spatial turbopumps, and a turbopump equipped with such an inductor.

STATE OF THE PRIOR ART

An inductor is a rotor part of a turbopump for drawing fluid into the pump thereof upstream of the paddle wheel compression stage (s). A turbopump with such an inductor is for example described in the patent application FR2765639.

The operation of the turbopump space inductors generally gives rise to an unstable operating range in which there are fluctuations of force on the inductor, due to the phenomenon of cavitation occurring in this operating range. These fluctuations can disturb the proper operation of the shaft line (rotor dynamics) or increase the wear of the blades of the inductor.

One solution for limiting the instabilities of cavitation within the inductor is to perform a beveling on the leading edge of the blades of the inductor. This inductor makes it possible to stabilize the zone of appearance of cavitation pockets forming on the upper surface, in which the pressure drop causes the formation of bubbles.

However, this bevel does not stabilize the extent of these pockets in the fluid flow direction, leaving a degree of freedom thereto. Instability remains, created by oscillations of the cavitation pockets, generating a hydraulic unbalance on the turbopump.

There is therefore a need for a turbopump inductor for stabilizing the cavitation pockets that appear at the blades of the inductor.

PRESENTATION OF THE INVENTION

The present disclosure relates to a turbopump inductor comprising a plurality of blades disposed between an inner casing and an outer casing, each blade having a lower surface and an upper surface, the extrados of at least one blade having a disbursement, the disbursement extending substantially from the leading edge of the blade to a walking surface arranged on the upper surface.

By extrados, one understands the surface of the blade located on the side of arrival of the fluid in the injector (upper face when the fluid crosses the injector from top to bottom). The disbursement corresponds to an area of the extrados. The presence of the disbursement on the extrados of the blade is characterized by the fact that instead of having a traditional profile, of normally non-concave section, the extrados of the blade presents in section in a plane perpendicular to the edge of the blade. attack of the blade, a thinned portion, concave or substantially concave, formed in hollow relative to the traditional profiles, and delimited downstream by a so-called walking surface. In other words, the disbursement amounts to removing, from a traditional blade profile, a layer of material on a predetermined surface of said blade. Therefore, the upper surface has a walking surface, corresponding to the existing slope between the extrados area having the disbursement, and the extrados area not having the disbursement.

The disbursement therefore implies a sudden change in the profile of the extrados. More specifically, the walking surface is a step, characterized by a substantially vertical wall joining two substantially horizontal surfaces, arranged at different heights from one another. For comparison, the existing beveling on the leading edge of the blades of some inductors, to limit cavitation instabilities, does not constitute a disbursement or a walking surface. Indeed, in this case, the thickness of the blade progressively evolves from the end of the bevel to the edge corresponding to the tangent between the beveled surface and the remainder of the blade. The evolution of the thickness of the blade is not discontinuous, but progressive. Conversely, the presence of a disbursement implies a discontinuity in the thickness of the blade, resulting in an abrupt change thereof.

Said disbursement extends substantially from the leading edge of the blade, corresponding to the upstream end of the blade, to the walking surface. By upstream end or downstream end of the blade, the ends are understood in a circumferential direction and in the normal direction of circulation of the fluid in the inductor. The position of the walking surface on the upper surface of the blade is determined, for example, by prior experimental tests carried out without disbursements, making it possible to study the shape of the cavitation pockets forming on the extrados of the blade. Preferably, the overall shape of the disbursement, and therefore the position of the walking surface, in a view along an axis of rotation of the inductor, corresponds substantially to the shape of the cavitation pockets, according to this same view, forming on the upper surface. By position of the walking surface, we understand 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.

Thus, when a cavitation pocket is formed 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 walking surface. The latter thus makes it possible to limit or eliminate the oscillatory movements of the cavitation pockets, is therefore to stabilize the dynamics of the inductor, thus reducing the wear of the blades of the inductor and the hydraulic unbalances acting on the shaft of the turbopump .

In some embodiments, the leading edge of the at least one blade has a bevelled surface, the disbursement extending from a downstream end of the beveled surface to the walking surface on the extrados.

The bevel surface, which can be made by machining, is a surface which is formed so that, in a sectional view of the blade along a cutting plane parallel to the axis of rotation of the inductor, the edge of attack locally involves a line segment.

This shape of the beveled surface, and therefore the leading edge of the blade, makes it possible to fix the cavitation pocket forming at said leading edge. The length of the cavitation pocket is thus delimited between this beveled surface and the walking surface.

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

In certain embodiments, the disbursement extends radially substantially from a radially internal limit of said at least one blade on the side of a central axis of the inductor, to a vicinity of leading edge, to a radially outer end of said at least one blade.

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.

In some embodiments, the walking surface, in a view along an axis of the inductor, has a variable radius of curvature of a radially internal limit of the blade on the side of a central axis of the inductor up to at a radially outer end of the blade.

In some embodiments, the disbursement is delimited by a bottom surface and the walking surface.

The bottom surface corresponds to the surface of the extrados on which the disbursement has been made, and has a shape, in a view along the axis of rotation of the inductor, corresponding to the shape of the cavitation pocket forming on the extrados, when the inductor is in operation. The bottom surface also has a relatively small curvature.

In some embodiments, the bottom surface and the walking surface are connected by a fillet.

This makes it possible to limit the stresses at the junction between the bottom surface and the walking surface, when the inductor is in operation.

In some embodiments, the upper surface has a downstream surface downstream of the walking surface, and the walking surface and the downstream surface are connected by a sharp edge.

In the same way as the bevel surface on the leading edge, this sharp edge makes it possible to fix the downstream limit of the cavitation pocket, preventing it from extending downstream from the walking surface. Therefore, the extrados of the blade having an upstream attachment area, on the leading edge, and a downstream attachment area, at the walking surface, fluctuations of the cavitation pocket forming on the extrados are thus limited, see deleted, thus reducing the dynamic instabilities during operation of the inductor, and thus reduce the wear of the blades of the inductor. In some embodiments, the thickness of the blade at the bottom surface, midway between the leading edge and the walking surface, in a view along a sectional plane parallel to an axis of the blade. inductor, has a value between 50 and 80% of the maximum thickness of the blade, preferably between 60 and 70%, more preferably between 65 and 67%.

These values of the thickness of the blade at the disbursement level make it possible to maintain the mechanical integrity of the blade during the operation of the inductor.

The present disclosure also relates to a turbopump comprising the inductor defined above.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention and its advantages will be better understood on reading the detailed description given below of various embodiments of the invention given as non-limiting examples. This description refers to the pages of annexed figures, in which:

Figure 1A shows a schematic sectional view of a non-disbursed blade leading edge, and Figure 1B shows a schematic sectional view of a dislodged blade leading edge.

FIG. 2A represents a perspective view of a turbopump inductor according to the present invention, and FIG. 2B represents the inductor of FIG. 2A, according to the enlarged view IIB.

- Figure 3 shows a schematic view of the inductor of the present invention along its axis of rotation.

FIG. 4 represents a sectional view of the inductor of the present invention along the line IV-IV of FIG. 3.

- Figure 5 shows a sectional view of a turbopump comprising the inductor of Figure 2A.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

In the following description, upstream and downstream is understood in the direction of rotation of the inductor, the leading edge of a blade being located upstream, and the trailing edge downstream.

Figure 1A shows a schematic sectional view of a portion of a blade 10 having a leading edge 22 and an extrados 20, without disbursement. The blade 10 is a blade of the inductor 1 represented on the different figures. The leading edge 22 has a bevelled surface 222, obtained for example by machining the leading edge 22, so as to obtain a blade whose upstream end 221 has a projecting angle.

When the blade 10 is in motion, a cavitation pocket

It can be formed at the leading edge 22. This cavitation pocket 30 is fixed on the protruding angle existing at the upstream edge 223 between the bevelled surface 222 and the extrados 20 of the blade 10. This cavitation pocket then extends over a portion of the upper surface 20. When the blade 10 is moving, the downstream end of this cavitation pocket 30 tends to fluctuate during the operation of the turbopump (arrow on the Figure 1A).

Figure 1B shows a schematic sectional view of the blade portion 10, this time presenting a disbursement. The disbursement is carried out by removal of material on the extrados 20, for example by machining, over a length, in the upstream-downstream direction, substantially corresponding to the length of the cavitation pocket forming on the extrados in the absence disbursement (Figure 1A).

Due to this disbursement, the extrados 20 of the blade 10 is divided into four surfaces: the bevelled surface 222, a bottom surface 24 corresponding to the extrados area comprising the disbursement, a walking surface 26 and a downstream surface 28, corresponding to the zone of the extrados not including the disbursement. The walking surface 26 makes the junction between the bottom surface 24 (hatches in FIG. 3) and the downstream surface 28, and makes it possible to compensate for the thickness variation of the blade 10 in this zone, generated by the removal of material.

Thus, when the cavitation pocket 30 is formed, its upstream end is fixed on the upstream edge 223, and its downstream end is fixed on the existing salient angle at the edge 261 between the walking surface 26 and the Downstream surface 28. Therefore, when the blade 10 is in motion, the cavitation pocket 30 is limited in its movements, its downstream end can no longer oscillate.

FIG. 3 represents a schematic view of an inductor 1 according to its axis of rotation, exhibiting a disbursement on each of its blades. The disbursement is delimited by the bottom surface 24, the upstream edge 223 and the downstream edge 261.

The upstream edge 223, corresponding to the downstream end of the bevelled surface 22, has, according to the view of FIG. 3, a curved shape that is 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 outer limit Le of the blade.

The downstream edge 261 also has, according to the view of FIG. 4, a curved shape, 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. The 'of the pale. In this example, the downstream edge 261 has the shape of an arc whose concavity is directed downstream. In addition, in this example, the radially internal limit Li of edges 223 and 261 are merged. On the other hand, the radially outer limit of the downstream edge 261 is situated further downstream than the radially outer limit Le of the upstream edge 223.

The shape of the disbursement 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 ridges 223. and 261 during the operation of the inductor.

In this example, the thickness e of the blade 10 at the disbursement level is approximately 65% to 70% of the maximum thickness E _ma of the blade 10 at the downstream surface 28. The thickness of the blade 10 being non-constant, the section considered for evaluating the thickness e corresponds here to the mid-distance between the upstream edge 223 and the downstream edge 261.

Preferably, the thickness e of the blade 10 is greater than 60% of the thickness E _ma x, whatever the section considered, so as to maintain the mechanical integrity of the blade 10. Moreover, the surface of bottom 24 and the walking surface 26 are connected by a fillet, clearly visible in Figure 2B. This makes it possible to limit the stresses at this junction, when the inductor 1 is in operation. FIG. 2A represents a perspective view of a turbopump inductor 1 according to the present invention, comprising a disbursement on each of its blades 10, each of them having a bottom surface 24, a downstream surface 28, a walking surface 26 and a bevelled surface 22. When the inductor 1 is integrated in a turbopump, the presence of the disbursements on the blades makes it possible to limit the fluctuations of the lengths of the cavitation pockets, and thus to stabilize the dynamics of the shaft of the turbopump by limiting the hydraulic unbalance caused by instationnales resumption of cavitation. This increases the life of the motor, without reducing the efficiency of the inductor.

Alternatively, the shape of the bottom surface 24 described above may be different, depending on the shape of the cavitation pockets forming on the extrados. 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 of the side of a central axis of the inductor, and a radially outer end of the blade 10.

FIG. 5 represents a sectional view of a turbopump 100 comprising the inductor 1 of the present disclosure, preferably intended but not exclusively for pumping fluid such as liquefied gas. The adjectives "axial" and "radial" are defined with respect to the axis of rotation A of the turbopump 100, while the adjectives "upstream" and "downstream" are defined with respect to the suction direction of the fluid. Considered according to the suction direction schematized here by arrows, the turbopump 100 successively comprises a suction stage 12, a centrifugal wheel 14 and an annular duct 16 for discharging the aspirated fluid. The suction stage 12 comprises the rotary inductor 1 provided 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 disposed downstream of the centrifugal wheel 14. The rotational shaft 110 also rotates the centrifugal wheel 14.

Although the present invention has been described with reference to specific exemplary embodiments, it is evident that modifications and changes can be made to these embodiments. examples without departing from the general scope of the invention as defined by the claims. For example, edge 261 and / or edge 223 may be not a sharp edge, but a dummy edge, in the form of a rounded surface such as a fillet. 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.

It is also obvious that all the features described with reference to a method can be transposed, alone or in combination, to a device, and conversely, all the features described with reference to a device can be transposed, alone or in combination, to a method.

Claims

1. Inductor (1) for a turbopump comprising a plurality of blades (10) disposed between an inner casing and an outer casing, each blade (10) having a lower surface and an upper surface (20), characterized in that the upper surface (20) ) of at least one blade (10) has a disbursement, the disbursement extending substantially from the leading edge (22) of the blade (10) to a walking surface (26) arranged on the extrados ( 20).

An inductor (1) according to claim 1 wherein the leading edge (22) of said at least one blade (10) has a bevelled surface (222), the disbursement extending from a downstream end of the bevel surface (222) to the walking surface (26) on the upper surface.

3. Inductor (1) according to claim 1 or 2 wherein the disbursement extends radially substantially of a radially inner limit of said at least one blade (10) on the side of a central axis of the inductor (1). at a vicinity of the leading edge (22) to a radially outer end of said at least one blade (10).

4. Inductor (1) according to any one of the preceding claims wherein the walking surface (26) 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 (1).

An inductor (1) according to any one of the preceding claims wherein the disbursement is delimited by a bottom surface (24) and the walking surface (26), the bottom surface (24) and the walking surface ( 26) being connected by a connection fillet.

6. Inductor (1) according to any preceding claim wherein the upper surface (20) has a downstream surface (28) downstream of the walking surface (26), and the walking surface (26) and the downstream surface (28) are connected by a sharp edge (261).

7. Turbopump (100) comprising the inductor (1) according to any one of the preceding claims.