JPH045402A - Integral shroud vane - Google Patents

Abstract

PURPOSE:To improve anti-vibration strength of a turbine blade and to make a new vane development easy by bringing adjacent integral snubbers into nearly face-to-face contacts with each other after arranging the projecting form integral snubbers on both surfaces of the vane being almost in the middle of a moving vane. CONSTITUTION:Integral snubbers 1 are arranged on both surfaces of the vane being in the middle of a blade 3 forming the major part of an integral shroud vane. Each of these integral snubber 1 is constituted so as to keep face-to-face contact with the blade 3 of the vane facing to its adjacent snubber 1. Since a vibration amplitude in the middle of vane can be restricted, its vibration mode can be also extinguished. Anti-vibration strength of a turbine blade can be increased in this way and at the same time a new vane development can be made so easily that its development cost can be reduced significantly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an integral shroud blade formed integrally with a blade of a turbine rotor blade.

[Prior art] Integral shroud blades used as conventional steam turbine rotor blades generally have a structure in which only the integral shroud 2 is attached to the tip of the blade, as shown in Figure 6. Met. In addition, in FIG. 6, 3 is a blade, and 4 is a blade root.

[Problem to be solved by the invention] As mentioned above, in the conventional integral shroud blade,
In this conventional structure, whether only an integral shroud is attached to the tip of the blade, there is a vibration mode (secondary mote) with a large vibration amplitude in the middle part of the blade. This situation is shown in the Campbell diagram in FIG.

As shown in FIG. 7, the blade vibration frequency of this vibration mote (secondary mode) is usually about twice that of the first mode, and exists below 8 harmonics (rotational order) in the long blade of the low pressure stage. Furthermore, this vibration mode consists of a large number of similar mode groups, and the variation in the blade frequency is large, so it is often difficult to avoid resonance at the rated rotation speed.

The present invention has been made in view of the above circumstances, and it is possible to eliminate the vibration mode (secondary mode) in which the vibration amplitude of the intermediate part of the blade is large and the vibration frequency of the blade is large and resonance is difficult to avoid. The problem to be solved is to provide le shroud wings.

[Means for Solving the Problems] The present invention applies a structure in which a protruding integral snubber (1) is attached to both surfaces of the integral shroud wing at approximately the middle portion thereof, as shown in FIG. This is characterized by the fact that the comrades (1) facing each other at their surfaces (see Fig. 4) are almost in contact with each other. In this structure, the cutting angle α of the contact surface of the integral snubber (1) is set to the integral shroud (
2) By making the cut angle β almost the same, the adjacent snares will be twisted back and deformed due to the centrifugal force during rotation.

(1) It is preferable to ensure that the comrades are in contact with each other.

[Function] Adjacent integral snubbers (1) attached to both surfaces of the integral shroud blade at approximately the intermediate portion contact each other, so that they have the effect of restraining the vibration amplitude of the intermediate portion of the blade. Therefore, it is possible to eliminate the vibration mode (second-order mode) in which the vibration amplitude at the intermediate portion of the blade is large and the blade frequency varies widely, as described above. That is, in the integral shroud blade of the present invention, as shown in the Campbell diagram in Fig. 5, only the first mode exists below 8 harmonics where the excitation force is large and it is necessary to avoid resonance, and therefore resonance does not occur. Avoidance becomes easier. Furthermore, since structural damping occurs due to contact between adjacent integral snubbers (1), vibration response can be reduced.

[Embodiment] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the same parts as in FIG. 6 are given the same reference numerals.

Fig. 1 is a perspective view showing the basic structure of an integral shroud wing, Fig. 2 is a plan view of an integral snapper directly related to the present invention, and Fig. 3 is a plan view of an integral shroud attached to the tip of the wing. Figure 4 is a view from the ■ arrow in Figure 3,
FIG. 5 is a Campbell diagram showing the vibration characteristics of an integral shroud blade equipped with an integral snubber.

In this embodiment, as shown in FIG. 1, a protrusion (hereinafter referred to as an integral snubber) is formed on both surfaces of the intermediate part of the integral shroud wing (the main part of the wing 3).
1 is provided. This integral snubber 1 is
As shown in FIG. 4, there is a structure in which the adjacent sand horns 1 and the corresponding blades (blades 3) are in contact with each other on their surfaces.

Here, in order to ensure surface contact between adjacent integral snubbers 1, the cutting angle α (see Fig. 2) of the integral snubber 1 with respect to the rotation axis is set to the cutting angle of the integral shroud 2. It is made almost the same as β (see Figure 3). Since this cutting angle β is usually 45° to 60°, the cutting angle α is also 45″ to 60°.

In the integral shroud blade having the above structure, the protruding integral snubbers 1 provided on both surfaces of the blade in the intermediate portion come into surface contact with the adjacent snubbers 1, thereby restraining the vibration amplitude of the intermediate portion of the blade. Become.

[Effects of the Invention] As detailed above, according to the present invention, a protruding integral snubber is provided on both surfaces of the integral shroud blade at approximately the middle portion thereof, so that adjacent snubbers are in almost surface contact with each other. By doing so, it is possible to restrain the vibration amplitude of the middle part of the blade, and this can eliminate certain vibration modes that have been a problem in the past, namely, the vibration amplitude of the middle part of the blade is large, and the variation in the blade frequency is large. It is possible to eliminate vibration modes (secondary modes) that are difficult to avoid resonance.

Furthermore, since structural damping occurs due to mutual contact between adjacent integral nuts, it is possible to reduce high-order moto blade vibration responses.

After all, according to the present invention, it is possible to improve the vibration resistance of turbine blades, and the development of new blades is facilitated.
Development costs can be significantly reduced.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the basic structure of an integral shroud according to an embodiment of the present invention, FIG. 2 is a diagram showing an embodiment of an integral snubber directly related to the present invention, and FIG.
The figure is a plan view of the integral shroud, Figure 4 is a view from the ■ arrow in Figure 3 to explain the contact surfaces between adjacent integral snubbers, and Figure 5 is a view of the integral shroud wing shown in Figure 1. 6 is a perspective view showing the basic eave structure of a conventional integral shroud wing, and FIG. 7 is a typical Campbell diagram of a conventional integral shroud wing. 1... Integral snubber, 2... Integral shroud, 3... Feather, 4... Wing root. Applicant's agent Patent attorney Takehiko Suzue Figure 2 Figure 3

Claims (1)

[Claims] In a shroud blade in which a shroud is integrally formed at the tip of a turbine rotor blade, a protruding integral snubber is provided on both surfaces of the blade at an approximately intermediate portion of the rotor blade, and the adjacent integral snubbers are in almost surface contact with each other. An integral shroud wing characterized by: