Patent Application
20180156183
There is provided a runner for a fluid machine. More precisely there is provided a runner for a fluid machine where the runner includes a runner hub and one or more curved blades, and where the blade is removably fixed to the runner hub by fixing elements that extend into a double curved first socket portion of the blade.
Runners for fluid machines are produced in many different forms and a diameter of up to three meters is foreseeable. One form of runner includes a runner hub and a number of blades spaced about the centre axis of the runner. Often the runner also includes a runner ring.
Runners have traditionally been produced as casted or welded-up structures that are subsequently prepared by grinding and machining. Increased efficiency and maintenance requirements have led to other production methods.
Norwegian patent 327520 discloses a runner of the type mentioned above but where a socket portion of removable blades fits in respective slots in the runner hub. The slots mainly follow the curvature of the blade. Both runner hub, blades and runner ring, if present are machined to a near finished state prior to assembly.
In order to achieve the required efficiency of the runner, blades of this kind has a relatively complicated, double curved form. Thus, the surface area between the blade and the bottom of the slot also has a double curved form. As each blade bears on most of the surface area, said double curved surface areas require a geometry having relatively close tolerances. It is self-evident that machining and necessary inspection work is time consuming and relatively costly for those relatively large double curved areas.
Other prior art documents disclosing relevant background technology are:
The invention has for its object to remedy or to reduce at least one of the drawbacks of the prior art, or at least provide a useful alternative to prior art.
The object is achieved through features, which are specified in the description below and in the claims that follow.
According to the invention, the contact between the double curved surface areas is replaced by a number of contact surfaces that are plane. The contact surfaces may be positioned at opposite sides or surrounding a fixing element that fixes the blade to the runner hub or runner ring. A contact body is positioned between the adjacent contact surfaces of the blade and the runner hub, alternatively the runner ring.
The invention is defined by the independent patent claims. The dependent claims define advantageous embodiments of the invention.
More specifically, the invention relates to a runner for a fluid machine where the runner includes a runner hub and one or more curved blades, and where the blade is removably fixed to the runner hub by fixing elements that extend into a double curved first socket portion of the blade, wherein the first socket portion bears against the runner hub at one or more localized contact surfaces that are plane, and wherein a contact body, which may be a separate body or form a part of the runner hub or blade, is positioned between one or more contact surfaces in the runner hub and the blade.
The contact body may typically be made from a metal, such as steel, and various geometrical shapes of the contact bodies are disclosed in the following. Other hard and substantially incompressible materials may also be used.
By introducing a number of plane contact surfaces, the surface areas of the runner hub and the blade become spaced apart. An accurately matching profile between them is no longer necessary.
The contact body is positioned between adjacent contact surfaces of the runner hub and the blade, and also between adjacent contact surfaces of a runner ring and the blade when a runner ring is present. The contact body may be a separate body or form a part of the runner hub, runner ring or the blade.
The contact surfaces, at least in the runner hub, runner ring or the blade, may be recessed. Thus, the plane contact surfaces may be machined to the correct depth through the surface areas of said items.
The length axis of the contact body may be parallel to the length axis of the fixing element. The contact surface is preferably perpendicular to the length axis of the contact body. In this way, the load capacity of the fixing element is optimally utilized and side movement of the blade during make-up avoided.
At least one of the socket portions may have a width that is wider than a thickness of the intermediate portion of the blade. The stability of the blade relative the runner hub and runner ring is thus increased.
The contact body may have any practical form that includes cylindrical form, ring form, disc form or elongated form or the contact body may be formed from a combination of two or more of these forms. In elongated form, the contact body extends across the socket portion.
The features according to the invention gives the advantages of:
In the following are described examples of preferred embodiments illustrated in the accompanying drawings, wherein:
On the drawings, the reference numeral 1 denotes a runner that includes a runner hub 2, a runner ring 4 and a number of blades 6 there between. The runner 1 has a central bore 8 for a shaft not shown.
In this preferred embodiment each blade 6 is, mainly for stability and erosion reasons, positioned in a first grove 10 in the runner hub 2, respective a second groove 12 in the runner ring 4 as shown in
A double curved first socket portion 14 of the blade 6 fits the first groove 10 and a double curved second socket portion 16 fits the second grove 12. The first and second socket portions 14, 16 have, again mainly for stability reasons, a greater width 15 than a thickness 17 of an intermediate portion 18 of the blade 6.
A number of fixing elements 20, here in the form of bolts, extends through bores 22 in the runner hub 2 and the runner ring 4 and into fixing bores 24, here in the form of threaded bores, in the blades 6 when the blades 6 are fixed in the runner 1.
As the intermediate portion 18 of each blade 6 has a complex double curved form, so have also the first socket portion 14 and the second socket portion 16.
The surface area 28 in the bottom of the first grove 10 constitutes according to prior art a contact area for a corresponding surface area 26 of the first socket portion 14. This prior art feature is for illustrative purposes shown as the first grove 10, here termed 10a, in the left part of
The invention discloses a number of localized, relatively small, plane contact surfaces 30 that are provided between the runner hub 2 and the blade 6, and the runner ring 4 and the blade 6 respectively.
Preferably, the plane of each contact surface 30 is perpendicular to the length axis 32 of the closest fixing element 20.
As shown in the middle and right blades 6 in
The length of the contact bodies 34 are adapted to the distance between the plane contact surfaces 30, and may be equal for all contact bodies 34 of a blade.
An angle 38 between the runner hub 2 and the blade 6 may vary along the length of the blade 6. The direction of the length axis 32 of the fixing element 20 relative the runner hub 2 may thus also vary.
In the figures the length axis 40 of the cylindrical contact bodies 34 are parallel to the length axis of the fixing element 20 when in its active position. This feature enables the fixing element 20 to sustain substantially axial forces only.
In another embodiment shown in
In an embodiment shown in
An elongated contact body 50 is shown in
It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb “comprise” and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article “a” or “an” preceding an element does not exclude the presence of a plurality of such elements.
The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20150679 | May 2015 | NO | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/NO2016/050105 | 5/25/2016 | WO | 00 |
