DE7232430U - Light vane for axial flow machine - Google Patents

Description

109/72 ES / er.

Public company Brown, Boveri & Cie. , Baden (Switzerland)

Light vane for axial flow machine

The invention relates to a lightweight blade for axial Turbomachine, the blade of which is formed from a core and a protective layer enveloping it, the core consists of a plurality of fibers laminated in a synthetic resin matrix.

There is a blade for turbo machinery known, which consists of a core made of plastic fibers and a synthetic resin matrix with an enveloping metal skin is formed, wherein the plastic fibers aligned in the longitudinal direction of the airfoil

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and these absorb the load on the airfoil in the longitudinal direction and transverse and torsional loads be absorbed by the metal skin.

In the case of these blades, it is precisely the advantage of their low weight, which forms the basis for the development of plastic blades, that is in question. Because the stress on the metal skin through transverse and torsional loads, its specific strength and thus the density must be increased significantly, which in turn results in greater inertia forces. In addition, an adjustment of the modulus of elasticity of the two materials is essential and therefore there is a restriction in the selection of the plastic or the fibers and the metal for the protective layer. However, this results in a very narrow field of application, since only a few metals simultaneously have sufficient strength with the same or almost the same modulus of elasticity as the plastic fibers and are also largely resistant to hydrolysis and erosion.

This is where the invention comes in, the task of which is to create a lightweight blade for turbo machines, which is opposite is largely independent of the above parameters, and in which the advantage of the low mass is retained without restriction remain.

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The inventive solution to the problem is characterized in that the fibers in at least three of each other different directions are laminated together in such a way that the fibers in a single direction the Absorb normal stresses on the loaded airfoil and the shear stresses from the loading of at least two fibers arranged in different directions can be accommodated, and the protective layer as non-load-bearing Skin is formed on the airfoil.

One of the advantages of this solution is the fact that even under harsh operating conditions the abrasion resistance is increased and the resin can be protected against hydrolysis without that one of the mechanical technological properties of the selected synthetic resin or the fibers has been taken into account must become. However, this also simplifies the production of blades for rough operation, since no technical tricks have to be used to increase the abrasion resistance to guarantee. In addition, it is then sufficient to apply very thin protective layers, for example 100 μm, made of metal to the plastic core, whereby on the one hand weight and on the other hand material can be saved. Here is the one to be expected Erosion on the shovel must be taken into account, i.e. the skin becomes somewhat thicker at the front edge of the shovel

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must be than, for example, on the suction side of a turbine blade, where it is less than 300 yum thick.

The natural frequency of the blade, which is the case with a blade made of pure plastic, is reduced by the thin protective layer is in a high range that is favorable for smoothness, only minimally influenced. This will change the vibration behavior of the airfoil compared to an airfoil with load-bearing protective layers or load-bearing protective layer much improved.

] By suitable selection of the protective layer material, the

j Resistance to droplet impact and erosion affects

! be flowing. For example, the use of

} Nickel or nickel with silicon carbide inclusions as protective

j layer material proved to be advantageous. In addition, can

j with a different composition of the flow medium by using pure cobalt or cobalt with tungsten carbide inclusions a similarly beneficial result can be achieved.

It is also possible to use alloys with the composition 15, 40% chromium, 0-20% tungsten and 0.2-2% carbon (all in percent by weight) and the remainder cobalt as a protective layer, with its good erosion resistance already as is known to be taken into account.

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Furthermore , when a compact or pore-free protective layer is used, a favorable influence on the entire composite material of the blade has been found, i.e. the tendency to hydrolysis has been significantly reduced since diffusion of the water or vapors into the plastic matrix is excluded due to the high density of the protective layer .

The invention will now be described on the basis of an exemplary embodiment described in more detail, with corresponding reference numerals being used in the individual figures for the same parts are. It shows:

1 shows a view of an airfoil according to the invention, FIG. 2 shows a cross section along the line A-A in FIG.

In Fig. 1, the blade 1 is shown in the torn open state in a perspective view. The core 2 of the blade 1 is formed by the individual laminates 3, U and 5, which are firmly connected to one another by means of synthetic resin during a pressing and curing process. It can be clearly seen that the fibers 6 of the individual laminates preferably run in several directions . The fibers 6 of the laminate 3 are arranged, for example, in the direction of the main generators of the airfoil 1, whereas the

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Fibers 6 of the other two laminates 4 and 5 in one of them directions deviating from certain angles.

A protective layer 7 is applied around this core 2, which on the one hand protects the blade 1 against erosion and droplet impact and on the other hand against hydrolysis. The protective layer 7 is made of an alloy in this exemplary embodiment the composition 30% by weight of chromium, 15% by weight of tungsten and 1% by weight Carbon, the remainder cobalt formed. This protective layer is applied to the surface of the plastic core 2 of the laminate Flame spray attached.

In FIG. 2, a cross section through the airfoil along the line A-A according to FIG. 1 is shown. The core 2 of the Blade 1 is formed by the individual laminates 3, U and 5, which are strung together in several layers, and the different directions of which are indicated by different hatching of the cross-sections of the fibers 6.

It is not to be regarded as essential to the invention whether the laminates 3, 4 and 5 are curved according to the blade profile are arranged. Because they can also, as shown here in a simplified manner, be laid more or less parallel to the blade chord. On the other hand, it is essential that the

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Fibers 6 of the various laminates 3, 4 and 5 in from one another are arranged in different directions with respect to the main generating end of the airfoil. This will make it » possible, not only the radial tensile forces, but also the transverse and torsional stresses as well as the shear stresses caused by the Pick up core 2 of the blade 1.

It also goes without saying that the laminates of the blade root, not shown, are constructed in the same way, the measures from manufacturing Seems necessary for the sake of simplification.

The core 2 is enveloped by the protective layer 7, in the case shown for the blade of a turbine, on the suction side 8 of the airfoil 1 a maximum thickness of the protective layer of JOO to be recorded. At the Shovel! Front edge 10 and the rear edge 11, the protective layer 7 is reinforced in order to increase due to the expected Erosion stress and the increased risk of droplet impact to take care of.

It can also be regarded as lying within the scope of the invention, the metallic protective layers by ceramic to replace, although on the special purpose and

the changed parameters of the coordination of the expansion and Elasticity behavior is to be taken into account within the framework of professional action.

Claims (3)

- 9 - 109/72 D jgfn s ρ r Ü c h e 1. A lightweight blade for an axial flow machine, the blade of which is formed from a core and a protective layer enveloping it, the core consisting of a plurality of fibers laminated to one another in a synthetic resin matrix, characterized in that the fibers (6) in at least three mutually different directions (3, 4, 5) are laminated with one another in such a way that the fibers (6) absorb the normal stresses on the applied blade (1) in a single direction (3) and the shear stresses from the stress of at least two in
fibers (6) arranged in different directions (4, 5) are received, and the protective layer (7) is designed as a non-load-bearing skin on the airfoil (1). 2 * lightweight shovel according to claim 1, characterized in that
that the skin is galvanically applied to the core of the blade . 3. Light shovel according to claim 1, characterized in that
that the skin is applied to the core of the shovel by flame spraying. - 10 - 109/72 D ι ». Light shovel according to claim 1, characterized in that that the skin by sticking to the surface of the airfoil (1) is attached. Public company Brown, Boveri & Cie.