JPS60240804A - Moving blade - Google Patents

Abstract

PURPOSE:To securely fix a predetermined blade in a moving blade having a columnar structure where each blade is inserted into an outer circumferential portion of a disc of a rotor, by arranging blades made of materials having a coefficient of thermal expansion greater than that of the disc at a suitable position of the moving blade. CONSTITUTION:A moving blade 3 has a columnar structure where each of blades 3a-3c is inserted into an outer circumferential portion of a disc of a rotor. A stopper blade 3a to be finally inserted is fixed by striking pins 5 between the same and adjacent blades 3b. Similarly, the pins 5 are struck between the blades 3b and adjacent blades 3c. The stopper blade 3a that is apt to be unstably fixed and the blades 3b and 3c that are subject to severe conditions in the viewpoint of strength are made of materials having a coefficient of thermal expansion greater than that of the disc. Thus, each of the blades 3a-3c is stably fixed, thereby achieving improvement in earthquake resistance and improvement in reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to improving the vibration resistance of rotor blades in a turbine.

[Background of the invention]

1 to 3 show an example of a structure for fixing rotor blades to a disk of a turbine rotor. As shown in FIG. 1, a rotor disk 1 is provided with a dovetail 2 in the circumferential direction on the outer periphery thereof. The legs of the rotor blade 3 shown in FIG. 2 have a shape that matches the shape of the groove 2, and these are inserted into the groove through an insertion part 4 that is normally provided only at one location around the circumference, and are sequentially inserted in the circumferential direction. sent to form a wing row. Therefore, when the grooves 2 are circumferentially filled with rotor blades 3 completely around the entire circumference, they are constrained with respect to movement in the circumferential direction by mutually adjacent rotor blades, and radially they fit into the grooves 2. Since it is constrained by its shape, it does not particularly require independent fixing means.

However, since the rotor blade 3a to be inserted last into the insertion section 4 cannot be fixed in the radial direction just by inserting it as it is, as shown in FIG.
and drive it into the rotor blade 3a and the adjacent rotor blade 3b.
is engaged with the circular groove 6 in the leg of the moving blade 3a.
to be fixed.

This moving blade 3a is called a ratio blade.

Further, a pin 5 is similarly driven between the rotor blade 3b and the adjacent blade 3c.

Conventionally, the materials commonly used are 12% chromium steel for the rotor blades and 1% chromium steel and 12% chromium steel for the disk materials, but these have a small coefficient of thermal expansion even at high temperatures, and Since they were similar, there was little difference in elongation due to heat.

On the other hand, since the rotor rotates at high speed, centrifugal force acts on the disk 1 and the rotor blades 3, 3a, 3b, and 3c, so a large tensile stress is generated in the circumferential direction of the dovetail groove 2 on the outer periphery of the disk 1. act.

For this reason, the dovetail groove 2 extends in the circumferential direction.

Further, since the rotor blade 2 tends to expand in the radial direction, when one rotor blade is considered, it contracts in the circumferential direction.

During high-speed rotation, as shown in FIG. 5, a gap 7 is generated between the rotor blades, and the fixation is not complete.

In addition, in the insertion groove of the rotor blade, the centrifugal force CF of the specific blade 3a is received by the adjacent rotor blade 3b, so the centrifugal force received by the leg of the blade 3b is 1.5 times CF, and the strength in this area is further increased. It's getting tougher.

For this reason, there is a method of reducing the centrifugal force of the ratio blade 3a to ensure strength.

Figure 6 shows a wing 3a with the legs of the wing 3a cut into a rectangular shape.
/ is shown in FIG. 7, and the profile part of the rotor blade is completely removed to form a catch 3a'.

However, these countermeasures have the problem that not only the number of processing steps is added, but also that the performance deteriorates because the stopper 38# does not have one rotor blade.

As described above, various problems occur if the wings are not completely fixed. In particular, the stress is severe near the blade insertion part, and
Due to instability there is a risk of fretting corrosion occurring.

In addition, since the working medium such as steam is partially injected at the governing stage of the turbine, each rotor blade is intermittently subjected to force.
Therefore, at the same time as receiving this intermittent force, the legs of the ratio blades 3a are displaced with respect to the disk due to the incomplete fixation mentioned above, and as a result, there is a risk of fritting corrosion and fatigue failure in the dovetail grooves 2, etc. arise.

In addition, if the rotor blades are incompletely fixed, the natural frequency of the rotor blades will decrease, creating a risk of resonance with the operating frequency.

[Summary of the invention]

The present invention arranges rotor blades made of a material with a higher coefficient of thermal expansion than the disk at appropriate locations among the rotor blades around the entire circumference,
This problem has been resolved.

That is, by using rotor blades made of such a material, loosening will not occur between the rotor blades when used in a high temperature range. Generally, thermal elongation is ΔQ,=α.・ΔT-Q0
...... (1) Here, Δ12D: Circumferential elongation of the disk α0: Coefficient of thermal expansion of the disk ΔT Temperature of the disk = Temperature of the rotor blade Qo: Disk circumference ΔQg=Σ α6 ・ΔT−Qg+ ... (2)Δ
Q11 = Amount of circumferential elongation αg of the rotor blade = Coefficient of thermal expansion of the rotor blade UB: From the above equation for the pitch of one rotor blade, if a material with a larger coefficient of thermal expansion than the disk is used for the rotor blade material, α8>α0. , ΔQg>ΔQo, so the gap 6 caused by one rotation can be eliminated.

[Embodiments of the invention]

FIG. 8 shows an example in which a rotor blade material having a large coefficient of thermal expansion is applied to a rotor blade insertion portion. In general, this material has high strength at high temperatures, so it is difficult to fix the fixed blade 3a and the rigid blade 3a is difficult to fix.
If this material is applied to b and 3c, it will be fixed tt? - In addition to corrosion and fatigue, there is no need to use clasps, which improves performance. Furthermore, the natural frequency of the blades does not decrease, resulting in a highly reliable blade cascade structure.

It goes without saying that fixation can be stabilized by arranging this material not only in the vicinity of the rotor blade insertion portion but also at appropriate locations around the entire circumference of the disk and designed in accordance with the usage conditions of the blade.

A desirable example of such a rotor blade material is Nimonik 80.
A (Nimonic 80 A), Nimonic 90 A (Nimonic 90 A), Inconel X (Inconel X), Refractalloy (Re
fractalloy), etc.

[Brief explanation of the drawing]

Figure 1 is a perspective view of the outer periphery of the disk, Figure 2 is a perspective view of the moving blade, Figure 3 is a perspective view of the ratio blade, Figures 4 to 6 are front views after installation of the ratio blade, and Figure 7 is after the clasp is installed. A front view, FIG. 8 is a front view when the present invention is applied to the airfoil attachment part. 3... moving blade, 5... bottle, 3a... ratio blade, 3b,
3c...The wing next to Hiyoku. 3rd illustration 4 prisoner #, 5″ 7 7 grass 6 eyes 3 α′ grass 7 prisoner 30,, “ $8 eyes

Claims (1)

[Claims] 1. A rotor blade having a row structure in which blades are inserted into the outer circumference of a disk of a rotor, characterized in that the blade is made of a material having a higher coefficient of thermal expansion than the material of the disk. Moving blade.