FR2839120A1 - Turbine wheel for hydraulic machine used for energy conversion, uses multi-facet blades with facets generated by rotation of a curve that is concave facing the turbine axis - Google Patents

Abstract

The turbine wheel (4) has orientable blades with as many facets (46) as there are blades on the wheel. Each facet is generated by rotation, over 360degrees around the axis of rotation (X5) of the blade, of a curve which is concave facing the turbine axis (Z-Z'). A radius from the center of curvature of the facet intersects the blade axis on the far side of the turbine axis.

Description

place said starter.

  The invention relates to a hub for a hydraulic machine equipped with adjustable blades. The invention also relates to a hydraulic machine comprising such a hub and to an energy conversion installation including such a machine. In the field of energy conversion, in particular in the field of the production of electrical energy from a waterfall, it is known to use a turbine with vertical or horizontal axis whose wind blades are arranged on the water flow path for

  rotate a device, such as an alternator.

  Such a turbine, which can be of the “Kaplan” or “bulb” type, comprises a wheel on which blades mounted which can be orientable, around an axis of rotation, in order to adapt the energy efficiency of the installation in relation to the flow of water passing through it. This allows the hub to rotate at a substantially constant speed, and to operate a

  alternator with stabilized output speed and frequency.

  With a conventional hub, the different possible orientations of the blades relative to the hub can induce the creation of interstices in which the water flows without generating any force on the hub, thereby reducing the total efficiency of the installation. In addition, bodies present in the water and passing around the turbine can be wedged or shredded in such interstices. To fill this type of interstices created by the phenomenon known as "calibration", it is known from WO-A ol / 61185 to equip the blades of a Kaplan turbine with a shutter flies of such an interstice. However, when the water flow rate around such a hub reaches relatively large values, cavitation phenomena develop caused by local accelerations of the fluids and by localized depressions downstream of interstices or surface irregularities in the 'water flow. These cavitation phenomena tend to decrease the efficiency and the operating power of a turbine, all the more so as the radius of the hub, which generally has a generally spherical shape over a part.

of its length, is small.

  Similar problems arise with other types of hydraulic machines and, in particular, bass pumps

"Deriaz" type fall.

  It is to these drawbacks that more particularly aims to remedy the invention by proposing a hub for a hydraulic machine which makes it possible to significantly reduce the cavitation phenomena, including at high flow rates, and without appreciable increase in the transverse dimensions of this hub relative to the state hubs

of technique.

  In this spirit, the invention relates to a hub for a hydraulic machine equipped with ables orient pales characterized in that the external surface of this hub comprises facets, in number equal to the number of blades, each facet being generated by a rotation, over 360 and around the axis of rotation of the corresponding blade on the hub, of a curve whose concavity is turned towards the axis of rotation of the hub, the center of curvature of the facet, in its intersection zone with the axis of rotation

  of the blade, being located, relative to this facet,

beyond an axis of rotation of the hub.

  Thanks to the invention, the various facets prewes on the hub have radii of curvature large enough to avoid or very strongly limit the phenomena of cavitation and calibration. In particular, the blades can pivot around their respective axes of articulation on the hub without creating annoying gaps between these blades and the hub, which

  for example, avoids the use of shutters.

  These different facets can be integrated into the hub without excessively increasing its radial dimensions, which allows the hydraulic machine comprising such a hub to keep a satisfactory size, while the radius of curvature of the outer surface of the hub in the vicinity blades may be large enough to severely limit or even

  suppress, cavitation phenomena.

  According to advantageous but not compulsory aspects of the invention, this hub incorporates one or more of the following characteristics: - The curve generating the facets is an arc of a circle, the facets thus being formed by a section of

sphere.

  - The curve generating the facets is an arc

  ellipse, parabola or hyperbola.

  - The precise center of curvature is located radially outside the hub, opposite the corresponding facet with respect to the axis of rotation of the hub. - The outer surface of the hub has transition zones whose centers of curvature, according to plans

  radial, wind located substantially on the axis of rotation.

  - The facets are generally tangent to a zone of revolution in their parts closest to

this zone.

  - The orthogonal projection, on the axis of rotation of the hub of the geometric center of a sphere section constitute a facet is located upstream from the orthogonal projection, on the same axis, of a midpoint of the facet taken a ml-distance between its upstream end point and its downstream end point. This aspect of the invention makes it possible to arrange the facets of the hub in such a way that they converge towards the downstream of the hub. The invention also relates to a hydraulic machine which comprises a wheel fitted with a hub as described above and on which a blade is mounted

  substantially in the center of each facet.

  Such a machine has an improved yield compared to

to those of the state of the art.

  According to an advantageous aspect of the invention, the axis of rotation of each blade on this hub forms, on the downstream side of

  the wheel, an acute angle with the axis of rotation of the wheel.

  It can also be provided that the leading edge of each blade is movable in an angular pivoting movement of amplitude greater than or equal to 40, around its axis of articulation on the hub, opposite the facet on which is mounted the blade. This avoids the appearance of a gap depending on the angle of inclination of the blade around its axis of

clean rotation.

  The invention finally relates to an installation for converting hydraulic energy into mechanical or electrical energy which comprises a hydraulic machine as previously described. Such an installation can be easily adjusted, while the cavitation phenomena induced by the flow of water are minimized or eliminated. The invention will be better understood and other advantages thereof will appear more clearly in the light of the

  description which will follow of an embodiment of a

  installation for converting energy and a Kaplan turbine wheel in accordance with its principle, given solely by way of example and with reference to the accompanying drawings in which: i - FIG. 1 is a schematic representation of the principle of an installation of production of electrical energy incorporating a Kaplan turbine and in accordance with the invention; - Figure 2 is a schematic perspective representation of the hub of the turbine shown in Figure 1; - Figure 3 is a side view of the hub of Figure 2; - Figure 4 is a section along line IV-IV in Figure 3, the internal elements of the hub being omitted, and Figure 5 is a side view of the turbine

  shown in Figure 1 in different configurations.

  The installation represented in FIG. 1 comprises a Kaplan type turbine 1 able to rotate around a generally vertical axis Z Z '. The turbine 1 is placed in a pipe 2 for the flow of water from an upstream reservoir. The flow is represented by the arrows E in FIG. 1. Wind direction 3 provided in the duct 2, upstream of the turbine 1 and makes it possible to partially regulate the flow E. The turbine 1 comprises a hub 4 and four blades 5,

  including wind trots visible in Figure 1.

  The hub 4 is centered on the axis Z-Z 'and contains mechanical elements for controlling the orientation of the blades around their respective pivot axes X5. The outer surface of the hub 4 is noted 41. This surface 41 comprises a part 42 of revolution centered on the axis Z-Z. We denote by R42 the radius of part 42. This

part 42 is upstream of the blades 5.

  Part 42 is connected to a frusto-conical part 43 inside which is a shaft connecting the wheel formed of elements 4 and 5 to a device for

  energy conversion, such as an alternator.

  The surface 41 also includes a frustoconical end portion 44, arranged downstream of the hub 4 and converging downstream, in the direction of the axis Z-Z '. Between the parts 42 and 44, the surface 41 is inscribed in an envelope surface S centered on an axis Z-Z 'and of oblong shape in the direction of the axis Z-Z'. The surface S has a symmetry of revolution around the axis Z-Z 'and lion notes R its radius in the plane of Figure 4. This

  radius R is of the same order of magnitude as radius R42.

  The intermediate part 45 of the surface 41, defined between the parts 42 and 44, forms four facets 46 which are formed by sections of a sphere whose radius R46 has a value greater than the distance between these facets

and the axis Z-Z '.

  Each sphere section is generated by the rotation, over 360 and around the axis X5 of the corresponding blade 5, of an arc of a circle 461 whose concavity is turned towards

the axis Z-Z '.

  We denote C46 the geometric center of a facet 46 which is. in fact, the center of curvature of the facet 46 in its central zone where it intersects the axis X5. As can be seen more particularly from FIG. 3, the center C46 of each facet 46 is located on the other side of the axis ZZ 'with respect to the facet considered, which corresponds to the fact that the value of R46 is very much higher to that of R a

Figure 4.

  Given the relatively large distance between the centers C46 and the facets 46, that is to say the relatively large value of the rays R46, in particular with respect to the value of R. the facets 46 are substantially flatter than the surface S In practice, the centers C46 i of the facets 46 are located radially outside the

hub 4.

  We define a point A1 as being the point of a facet 46 closest to the area 42. We define a point A2 as and ant a point of this facet 46 farthest from the part 41. We can then define a point median A3 as and taken on facet 46 halfway between points A1 and A2. We note A'3 the orthogonal projection of point A3 on the axis Z-Z '. We also note C'46 the orthogonal projection of the geometric center C46 of the facet 46 considered on the axis Z-Z '. The point C'46 is located on the axis Z-Z 'upstream of the point A'3, which corresponds to the fact that the facet 46 is generally

  converging towards the axis Z-Z 'going downstream.

  Furthermore, the facet 41 is flush with the

surface 42 at the point A1.

  Between two facets 46, a transition zone 47 is provided in which the surface 41 follows the surface

  envelope S. that is to say is centered on the axis Z-Z '.

  Each facet 46 is thus delimited by an edge 48 whose geometric appears more clearly in FIGS. 2 and 3 and which constitutes the edge of junction between the facet 46

  and the adjacent transition zones 47.

  As a variant, the edge 48 can be replaced by a connecting conge between the facet 46 and the adjacent zone 47, the use of a conge making it possible to soften the

  transition between these two geometric entities.

  As it emerges more particularly from Figures 1 and 5, the axes X5 of articulation of the blades 5 on the hub 4 can form on the downstream side of the hub, an acute angle,

around 80, with the axis Z-Z '.

  The axes X5 pass through the facets 46 at or near their respective midpoints A3, so that each blade 5 can rotate with an amplitude of about 40 A, around its axis X5, while its leading edge 51 remains opposite a facet 46. In its zone d / intersection with a facet 46, an axis X5 is

  generally perpendicular to this facet.

  We note 52 the blade mounting flange 5 relative to the hub 4, this flange being kinematically controlled by the elements housed in the hub 4. We can conform the internal radial edge of the internal blade 5, which exceeds the flange 52 , with a radius of curvature identical or close to the radius R46, so that, independently of the angular orientation of the blade 5 shown respectively in solid lines and in broken lines in FIG. 5, no additional gap is created between the blade 5 and the face 46, between the leading edge 51 and the

flange 52.

  In FIG. 5, two positions of the blade 5 have been shown with angles of inclination p1, p with respect to the axis Z-Z 'which are approximately 20 and 40 respectively. In practice, the invention makes it possible to rotate the blade 5 up to a value of angle of inclination of the order of 40 while keeping the leading edge 51 of the blade 5 in

look of facet 46.

  The construction of the hub 4 therefore makes it possible to limit the phenomena of cavitation and the creation of gaps near the leading edge of a blade while retaining

  an adjustable character to the turbine which it equips.

  The invention has been represented with facets in the form of a truncated sphere, generated by the rotation of an arc of a circle 461 around an axis X5. Wile is however applicable with facets of different geometries, for example generated by rotation under the same conditions of an arc of ellipse, parabola or hyperbola whose

  concavite is turned towards the axis of rotation of the hub.

  i The invention was represented lows of its use with a Kaplan type turbine. Wile is however applicable to other types of turbines and pumps

  low fall, particularly of the <c Deriaz >> type.

  The invention has been represented with a turbine equipped with four blades but is applicable regardless of the number of blades, the number of facets being adapted to the number of blades. J

Claims (11)

  1. Hub (4) for a hydraulic machine (1) equipped with orientable blades (5), characterized in that the surface external to said hub comprises facets (46), in number equal to the number of blades, each facet being generated by a rotation, on 360 and around the axis (X5) of rotation of the corresponding blade (5) on said hub (4), of a curve (461) whose concavity is turned towards the axis of rotation (Z- Z ') to said hub, the center of curvature (C46) of said facet (46), in its zone of intersection with the axis of rotation (X5) of the blade (5), being located with respect to said facet , beyond said axis of rotation (Z-Z ') to said hub. 2. Hub according to claim 1, characterized in that said curve is an arc (461), said   facet (46) thus being formed by a truncated sphere.   3. Hub according to claim 1, characterized in that said curve is an elliptical, parabolic arc or of hyperbola.   4. Hub according to one of the preceding claims,   characterized in that said center of curvature (C46) is located radially outside said hub (4), opposite said facet (46) relative to said axis of rotation (Z-Z ').   5. Hub according to one of the preceding claims,   characterized in that said external surface (41) to said hub (4) comprises transition zones (47) whose centers of curvature (C), along radial planes (FIG. 4), wind located substantially on said axis of rotation ( Z z ').   6. Hub according to one of the preceding claims,   characterized in that said facets (46) are generally tangent to a zone of revolution (42) in   their parts (A1) closest to said zone.   7. Hub according to one of the preceding claims,   characterized in that the orthogonal projection (C'46) on said axis of rotation (Z-Z ') of the geometric center (C46) of a sphere section constitute a facet (46) is located upstream with respect to the projection orthogonal (A'3) on said axis of a midpoint (A3) of said facet taken at ml-distance between its extreme upstream point (A1) and its downstream extreme point (A2).   8. Hydraulic machine (1) comprising an equipped wheel   a hub (4) according to one of the preceding claims   and on which a blade (5) is mounted substantially at center (A3) of each facet (46).   9. Machine according to claim 8, characterized in that the axis of rotation (X5) of each blade (5) on said hub (4) forms, on the downstream side of said wheel, an angle (a)   acute with the axis of rotation (z-Zi) of said wheel.   10. Machine according to one of claims 8 or 9,   characterized in that the leading edge (51) of each blade (5) is movable in an angular pivoting movement of amplitude greater than or equal to 40, around the axis of rotation (X5) of said blade on said hub, only opposite the facet (46) on which is mounted said blade.   11. Installation for converting hydraulic energy into mechanical or electrical energy, characterized in that it comprises a machine (1) according to one of claims 8 to 10.