JPS59504A - Rotor of steam turbine - Google Patents

Abstract

PURPOSE:To eliminate the variation of restrictive force for the vibration of a blase and enable the accurate detunning design of the titled device by a method wherein a clearance between each of the blade built-in part is adjusted within the specific dimensional range, an attenuating plate is engaged and fixed into a projection of the built-in part of a blade, then said plate is also engaged and fixed into other blade. CONSTITUTION:At the build-in handling of a blade, a clearance between adjacent each built-in part 2 is adjusted within the range of 0.05-0.2mm.. Two projections 8 separated in radial direction are provided on the axial direction side surface of each built-in part 2, a hole 9a of a ring-shaped attenuating plate 9 is fitted with said projections 8, then fixed by caulking, accordingly, the adjacent built-in plates 2 are jointed.

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a steam turbine rotor having rigidly mounted blades.

[Technical background of the invention]

Steam turbine blades are generally exposed to a high centrifugal force field, and as a result, in addition to being subjected to large centrifugal stress, fluid force due to non-uniform wake flow from the nozzle 9 Fluid brim gravitational acceleration due to non-uniform flow on the circumference, etc., act as excitation forces. In addition, vibration stress is added, so the situation is often extremely severe from a stress standpoint.

In particular, fatigue caused by vibration stress has a serious effect on the reliability of blades. Damage to the vane shroud or tenon,
It is thought that most of the cracks that occur in the effective part of the blade or the implanted part are caused by fatigue. Therefore, suppressing blade vibration has become one of the most important themes in blade design, and conventional efforts have been made to reduce vibration stress based on two main concepts as shown below.

The first idea is to give the blades damping properties against vibration by, for example, using a reshroud with racing wires and ears attached to the blades.

Second Concept Since most of the excitation force applied to the blade has a frequency that is an integral multiple of the rotational speed, the frequency that is an integral multiple of the rated rotational frequency and the natural frequency of the blade are detuned. First, the first concept will be explained using a conventional blade having a saddle-shaped implant as an example. FIG. 1 is a cross-sectional view of the state in which the blades are embedded in the rotor, viewed from the tangential direction. FIG. 2 is an axial view of the blades installed in the rotor. (1) is the effective part of the blade (2)
is implanted into the wheel (5) by saddle-shaped implantation and retraction. (3)
is fixed to the blade by caulking the tenon (4) with the shroud.

Here, the shroud (3) serves to dampen the vibrations of the blades and adjust the specific number of motions.

Although the blade shown in this figure is not provided with it, it is generally widely used to provide vibration damping properties with a racing wire or the like. However, these methods focus only on suppressing vibrations in the effective part of the blade. In actual blades with saddle-shaped implants, vibration occurs in the implant during rotation, and it has become clear that conventional vibration countermeasures alone are not sufficient.

- This will be explained in detail below. As shown in Figure 2, when the blade is implanted, the adjacent implanted part (2)
, (2) The comrades are hitting it hard. This is done by pushing in the stopper blade when implanting the blade, and the contact surface pressure between the implanted parts is approximately 3 to 5 Y/-. However, during rotation, due to the influence of centrifugal force, the tangential stress on the outer periphery of the wheel generally reaches 7 Ky/my4 or more, and the blade implant itself contracts in the tangential direction by Poisson's ratio as it is pulled by the centrifugal force. , the contact pressure between the implanted parts during rotation becomes zero, and a small gap is created between the implanted parts.

For this reason, the implanted portion has almost no restraining force with respect to vibrations vibrating in the tangential direction, causing vibration of the implanted portion as shown by arrow (6)K in FIG. 3. If the implanted part (2) of the blade vibrates during rotation in this way, not only is there a risk of repeated stress being applied to the implanted part (2) itself, causing serious defects such as cracks, but also Since the restraining force against the vibration of (2) is eliminated, the damping force of the blade vibration is largely due to the shroud (3) or tenon (4) (or racing wire). Increase.

As described above, it has become clear that the loss of the vibration restraining force of the saddle-shaped implanted part of the blade is a serious factor that reduces the reliability of the blade.

Next, the second way of thinking will be explained. Generally, the implanted part (2
) is completely fixed and the natural frequency of the blade is analyzed by the finite element method.If the change in the natural frequency of the pair of blades in the system due to centrifugal force is drawn on a Campbell diagram, it becomes as shown in the fIg4 diagram. As described above, in a blade having a saddle-shaped implanted portion, the change in natural frequency due to increase in rotation is not uniform, but has a range as shown in range (7).

This phenomenon is caused by the fact that during rotation, as the rotation increases, the restraining force against vibration of the saddle-shaped implant (2) decreases, so the natural frequency tends to decrease, and this is caused by the centrifugal force. This is thought to occur because an attempt is made to cancel out the increase in vibration frequency. However, when implanting the blade, the contact pressure between the implanted parts (2) and (2) of each blade is not uniform, and the tendency for the natural frequency to decrease differs depending on the blade, so it is unique within a range like this. The vibration frequency changes.

[Problems with background technology]

With the current technology, it is not possible to quantitatively grasp the reduction in the restraint force against vibration of the implanted part and the accompanying reduction in the natural frequency at the design stage. Therefore, it is difficult to design a blade that detunes the natural frequency of the blade from an integral multiple of the rated rotational frequency.

[Purpose of the invention]

An object of the present invention is to provide a rotor for a steam turbine that suppresses vibrations of blade implants, eliminates changes in restraint force against blade vibrations, and enables accurate detuning design. .

[Summary of the invention]

In the present invention, the gap between the implanted parts of the blades is set to 0.05
-0.2 order, a protrusion is provided on the axial side of the implanted part of the blade, a damping plate is secured and fixed to this protrusion, and this damping plate is engaged and fixed to the protrusion of another blade or the wheel. By doing so, the contact surface pressure between the implants is reduced to zero even when they are at rest, so that the restraining force against vibrations of the implants hardly changes when the implants are at rest and when rotating, and even if the implants try to vibrate, it is damped. This enables accurate KL and IIIv4 design to suppress vibrations due to friction with the plate.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. FIG. 5 shows a part of a rotor of a steam turbine seen from the axial direction with blades having saddle-shaped implants embedded in the wheel, and shows the conventional rotor shown in FIGS. 1 to 3. Components that are the same as those in the above are given the same reference numerals and their explanations will be omitted.

In this embodiment, two protrusions (8) are provided on the axial side surface of the implant (2) of each blade, spaced apart in the radial direction, and the implant (2) of the adjacent blade , 12) Annular damping plate (9) K hole (9a) to connect the two
Open it up, fit it in, and swage it in place. Also, here,
At the time of implantation, adjust the gap between adjacent implanted parts (21, (2) by 0.05 to 0.2 by using shims (not shown). This is the same as the conventional example shown in FIGS.

Next, the effect will be explained.

Even if the implanted portion (2) of the rotor blade tries to vibrate, the vibration is suppressed by the frictional action with the damping plate (9). In particular, the vibration damping effect of this damping plate (9) is
mode in which it vibrates so that it rotates tangentially to the rotor (
(see arrow 6 in FIG. 3) is large, and repetitive vibration stress generated near the end face of the implanted portion can be suppressed to a low level. Most of the cracks that occur in the implanted portion (2) K originate from the end faces, but the occurrence of these can be drastically reduced by lowering the vibration stress at the end faces. At the same time, by reducing the vibration of the implanted part, the vibration stress applied to the shroud (3) and tenon (4) can also be suppressed to a low level.

In addition, there is a gap of 0.05 to 0.2 R between the adjacent implanted parts (2) and (2) in the implanted state, and the contact surface pressure is zero from the time of rest. Therefore, the restraining force against vibration of the implanted portion (2) hardly changes either when it is stationary or when it is rotating. Therefore, the tendency for the eigenvalue to decrease as the rotation increases, which was observed in conventional blades with saddle-shaped implants, disappears, and only the tendency for the eigenvalue to decrease due to centrifugal force appears. Therefore, by analyzing the increase in the natural frequency due to centrifugal force, the natural frequency at the rated rotation can be accurately determined, and a complete detuning design can be performed.

In another embodiment shown in FIG.
It was inserted into II and caulked. The rest is as shown in Figure 5.

Therefore, in addition to having the same distribution effect as explained in FIG. Implant N
5 This has the effect of reducing the burden of (2).

In another embodiment shown in FIG. 7, the damping plate (9) is annular and has an extending portion I in the inner diameter direction, and the annular portion is similar to that in FIG. (2) The extension part (11) is connected to the protrusion of the wheel and fixed by caulking as shown in Fig. 6, and the other 4 degrees are as shown in Fig. 5.

Therefore, the effect explained with reference to FIG. 6 is exactly the same.゛It should be noted that the present invention is not limited to the embodiments described above and shown in the drawings, and the present invention is not limited to the embodiments described above and shown in the drawings.
Of course, it can be implemented with various modifications.

〔Effect of the invention〕

As explained above, according to the present invention, the vibration of the implanted part of the blade can be suppressed to a low level, and the occurrence of cracks in the implanted part can be drastically reduced. Since the burden on the implant can also be reduced, damage to areas other than the implanted area can also be reduced. Furthermore, since it is possible to design a blade in which the natural frequency of the blade is accurately detuned from the frequency that is an integer multiple of the rated operating frequency, it is possible to provide a steam turbine rotor that has small vibrations during rated operation. Therefore, it can reduce blade accidents, which are the most common accident in steam turbines, so it has a high degree of social contribution.

[Brief explanation of drawings]

Fig. 11 is a vertical cross-sectional view of the upper half of a conventional steam turbine rotor, Fig. 2 is a side view of the main part of Fig. 1, Fig. 3 is a perspective view of the blade of Fig. 1, and Fig. 4 is a vertical sectional view of the upper half of the rotor of a conventional steam turbine. Campbell diagrams of conventional blades and FIGS. 5 to 7 are side views showing essential parts of different embodiments of a rotor for a steam turbine according to the present invention. 1... Effective part of the blade 2... Implanted part of the blade 3...
・Shroud 4... Tenon 5... Wheel
8, 10... Protrusion 9... Damping plate 1
1...Extension Department Agent Patent Attorney Mr. Inoue Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (3)

[Claims] (1) In a steam turbine rotor in which a plurality of blades are radially connected to a wheel at saddle-shaped implants, the blades are implanted so that the gaps between the blade implants are in the range of 0.05 to 0.2 wx, Fixing of a steam turbine, characterized in that a projection is provided on the axial side surface of the implanted part of the blade, a damping plate is fixed and fixed to the projection, and this damping plate is fixed and fixed to the projection of another blade or the wheel. Child. (2) A rotor for a steam turbine according to claim 1, wherein the damping plate is annular and the blades are connected to each other. (3) A rotor for a steam turbine according to claim 1, wherein the reduced plate is annular and has an extending portion in the inner diameter direction, and is coupled and fixed to a wheel at the extending portion.