JPS5960004A - Device for fixing turbine blade - Google Patents

Abstract

PURPOSE:To prevent the dispersion of natural frequency of blades by a method wherein a non-contact surface ranging from near neck part of the buried part toward a burying direction is arranged at the adjoining side surfaces of the buried part of outside dovetail shape. CONSTITUTION:A tapered non-contact surface 5 ranging from near the first hook at the buried part 3 to the neck part is formed at one side surface of outside dovetail shape of blade 1. With such an arrangement, the representative length of the blade determining the natural frequency of it can be of the same value even if a clearance CL1 is produced between the buried parts 3 under a centrifugal force or the side surfaces of the buried parts 3 are contacted in face-to-face condition, resulting in that a dispersion of the natural frequency can be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improved turbine blade fixing device that reduces variations in the natural frequency of the blade during operation.

[Technical background of the invention and its problems]

The blades of a steam turbine, together with the nozzles and stator vanes, not only affect the efficiency of the turbine, but also have the issue of strength against vibration and centrifugal force, which directly affects efficiency, safety, and durability. It is one of the most important structural parts.The methods of fixing the blades to the rotor include fitting them into grooves such as T-shaped, sawtooth, and dovetail shapes, and vice versa. A rotor, etc. (there are some that fit two together).

In other words, in FIG. 1 (which shows a two-sided outside dovetail-shaped turbine blade implantation part), the lower end of the blade 1 (the implantation part 3 having a two-saw polyhedral shape U2 is formed, and the head part ( A shroud 4 is provided for suppressing steam leakage and vibration.The steam turbine blades are assembled by fitting the many blades 1 to a rotor (not shown) as shown in Figure 2 (see Figure 2). The assembled blades should be in contact with each other (2) on all sides of the adjacent implanted portions 3, that is, on the sides a-b-c-d of Fig. 2. It is assembled.

In the state where the conventional blade is implanted, the entire implanted part 3 is in surface contact at the side surfaces a-b-c-d, so the blade 1
The characteristic frequency of is the representative length L of the implantation shown in Figure 1.
It is determined by l. Even in the operating state of the turbine, since the effective part of the blade 1 has a small mass (2), it is operated with this surface contact, so the unique frequency is determined by the narrowing length Ll (2 and p As shown in the Campbell diagram in Fig. 5, it is said that there is no variation in the two-pronged frequency.

However, the blade has a large mass in the effective part (for two reasons,
Centrifugal force (as shown in Figure 3, the implanted part 3
2. Therefore, since the ratio of displacement in the outer circumferential direction from the stationary state indicated by the dotted line to the state indicated by the solid line increases, the side surfaces a-b of the implanted portion 3
-c-di The surface pressure applied to the second part cannot be maintained, and the first
Hook xi + X2 l of the implanted part 3 of the blade 1 shown in the figure
The entire blade is held only by the part XB (-). In this state (2), the frequency of the 10 blades is determined by the representative length L2 on the hook Xl shown in Figure 1. (2) In the actual operating condition of the turbine, a clearance CL2 is created between the implanted parts 3 as shown in Figure 3 (2) due to the release of surface pressure caused by centrifugal force, but this clearance CL2 is small. When it is in (
Or, for some blades, the hook part X is the fulcrum, and sometimes (some blades) are in a surface contact state. exhibits,
Also, there will be variations between them (second issue).

Within the range of the short blades, the centrifugal force causes the implant 3 to
Even if the surface pressure on the side surface of the blade is released, the blades are designed to have sufficient strength against resonance (LF design), and the unique frequency of the blades is high, so even if the blades are in a resonance state, Due to the high order of resonance expressed as the ratio of the characteristic frequency of the blade 1 to the operating speed, the stress level is low enough not to cause damage to the blade (-). -For blades with similar lengths that have similar individual frequencies, the order of resonance is low, so the occurrence of variations as shown in Figure 6 indicates that there is a possibility of damage to the blades.Special (- Such long blades are used to control the humidity of steam and the poor quality of the steam, so it is necessary to ensure detuning (two steps).

[Purpose of the invention]

The purpose of the present invention is to reliably eliminate variations in the unique frequencies of the blades during operation (secondly, to provide a fixing device for turbine blades that can ensure detuning and significantly reduce the possibility of damage). There is something to do.

[Summary of the invention]

The present invention is characterized in that the assembled state of the blade (2) is that surfaces of adjacent implanted parts are provided with surfaces that do not contact each other (2), even if the blade is fixed on the side of the implanted part, the centrifugal force This relates to a turbine blade fixing device that has two configurations so that even if the blade is fixed at the hook part, the representative length that determines the unique frequency of the blade is the same.

[Embodiments of the invention]

The present invention will be described below with reference to an embodiment shown in FIG. That is, in the present invention (2), the non-contact surface 5 of the Taber surface is formed from the vicinity of the 17th hook x1 on one side of the implanted part 3 of the blade 1 to the neck of the implanted part, and the adjacent blade The side surface of the implanted portion 3 of the second implantation portion 3 has a tapered surface as shown in FIG. Forming the non-contact surface 5 of the surface (second point, points e-be-e' and c
-f-f' forms the polygon, and the point a-e-e'-f'-
C2 is to form a surface 5 that does not come in contact with f-d. In addition, the vicinity of the 17th hook This is because, since they are not exactly the same, there may be a difference in the frequency of each fixation (=), so it is necessary to determine the optimum value based on this.

a-e-e'-f' of the non-contact side surface 5 of the implanted part 3 of the blade 1
The shape of -f-d is determined at the point closest to the effective part C of the blade of the implanted part 3 according to the shape and length of the effective part of the blade 1, so that the side surfaces do not come into contact with each other during resonance (Fig. 4). The shape of the non-contact side surface 5 of the implanted part 3 is determined by the table clearance CLI as shown in FIG. The tapered surface 8, the tapered surface 9 on one side in FIG. 10, and the tapered surface 10 on both sides in FIG.
Any structure that can secure the clearance CLI may be used.

〔Effect of the invention〕

As described above (2) According to the present invention (2), a surface that does not come into contact with the adjacent implanted part is formed on the side surface of the implanted part of the blade. The representative length that determines the frequency can be kept constant at all times.Therefore, there is no variation in the unique frequency of each blade, and sufficient detuning for resonance can be achieved, so the blade Accidents caused by resonance can be prevented.

[Brief explanation of drawings]

Figure 1 is a side view showing the blades of a steam turbine, Figures 2a and b are front and side views showing the fixed part of the turbine blade, and Figure 3 explains the deformed state of the fixed part (-) of the turbine blade. Figure 4a and b are front views for the present invention (
5 is a front view and a side view showing an example of a fixed part of a steam turbine according to the second embodiment; FIG.
Figure 6 shows the unique frequency of the turbine blade during operation (−).
The Campbell diagram in a state where fluctuation occurs, and FIGS. 7 to 11 are front views of a fixing part showing another embodiment of the present invention (a side surface shape in which two adjacent blade implanted parts do not contact each other). 1... Vane 2... Implant groove 3... Implant part 4... Shroud 5, 6.7.8.
9.10...Non-contact surfaces CLI, CL2...Clearance a -e -e'-f'-f-d...Non-contact sides e-b-e' and f'-c-f...・Contacting side surface xl l X2 + X3...Hook part (8733
) Agent Patent Attorney Yoshiaki Inomata (and 1 other person) / Ha (b) 17 Figure 4! <o-) (b) Fig. 5 12 Fig. 6/2 Fig. 11

Claims (3)

[Claims] (1) A turbine blade having an outside dovetail-shaped implanted portion (-) that does not contact the side surfaces of adjacent implanted portions over a predetermined range C2 extending from the vicinity of the neck of the implanted portion toward the implantation direction. A turbine blade fixing device characterized by having a surface. (2) A patent characterized in that the representative length of the non-contact surfaces, which determines the natural frequency of the turbine blade during operation, is constant, and the variation in the unique frequency is set to a minimum (-) range. A turbine blade fixing device according to claim 1. (3) The turbine according to claim 1, wherein the non-contacting surface is established in an outside dovetail-shaped implanted portion (2) in a range from the neck of the implanted portion to the first hook portion. Feather fixing device.