JPS61252804A - Device for coupling tip of moving vane of turbine - Google Patents

Abstract

PURPOSE:To improve the vibrating property of a moving vane assembly, by providing dovetail grooves in the front and rear projections of the tips of moving vanes, providing joiners with blades, and inserting the joiners into the dovetail grooves. CONSTITUTION:The tip of each of moving vanes 1 are provided with front and rear projections 2, 3. The adjacent projections 2, 3 of the moving vanes 1 are located in contact with each other. Dovetail grooves 7 are provided in the peripheral surfaces of the projections 2, 3. Joiners 8 are inserted into the dovetail grooves 7 to couple the moving vanes 1 to each other. blades 9 project from the peripheral surfaces of the joiners 8. The moving vanes 1 are thus coupled together along the total circumference of a moving vane assembly to improve its vibrating property.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a device for connecting turbine rotor blades at their tips and preventing fluid leakage between the tips of the rotor blades and an outer peripheral wall.

[Background of the invention]

There are many different types of device structures that connect turbine rotor blades to each other using connecting members, but among them, there is a device and structure that connects all the blades around the entire circumference in a circumferential direction so that there is no break in the blades. .

This structure is collectively referred to as a full-circumference one-ring structure, whereas a structure in which a plurality of blades are connected in a circumferential direction is simply referred to as a group blade structure. Comparing these blade structures in terms of their vibration characteristics, when the same type of blade has a group structure, the number of unique vibration modes is generally larger when the blade has a one-ring structure all around the circumference. However, in general, when receiving an excitation force with a frequency that is an integral multiple of the turbine rotation speed, the number of resonance points is much smaller than in the case of a group true, so it is important to design blades that avoid resonance within the turbine operating range. It is well known that it is very advantageous to do so.

As an example of what can be achieved by connecting the rotor blade tips to achieve such a one-ring structure all around, for example, Japanese Patent Laid-Open No. 52-14
As shown in Publication No. 107.

It is known to connect adjacent rotor blades by inserting a connecting piece into a groove provided at the tip of the rotor blade, and it is possible to realize a blade structure with no problems in terms of vibration characteristics. However, there is generally a gap between the tip of the rotor blade and its outer peripheral wall, and there is a problem in which the working fluid leaks and flows from upstream to downstream without doing any work. In this example, no leakage prevention measures are taken.

On the other hand, regarding the prevention of leakage at the tip of the rotor blade, as shown in Fig. 3, fins extending in the circumferential direction are provided on the tip of the rotor blade or the outer circumferential wall, and a structure prevents leakage by the effect of a so-called labyrinth seal. There is. However, with this structure,
In order to improve leakage prevention performance, it is necessary to make the fin gap as small as possible, but in cases where the rotor blades have a large elongation in the radial direction due to centrifugal force during rotation, or when there is large thermal deformation of the rotor blades or outer peripheral wall, The fin gap cannot be made too large, resulting in a significant drop in leakage prevention performance.

[Purpose of the invention]

An object of the present invention is to provide a device that seamlessly connects all rotor blades around the entire circumference at the tip of the rotor blade and prevents fluid leakage between the tip of the rotor blade and the outer peripheral wall.

[Summary of the invention]

A feature of the present invention is that at the tip of one rotor blade, protrusions are provided that extend toward the ventral side and the dorsal side of the rotor blade, respectively, in a direction substantially perpendicular to the longitudinal direction (radial direction) of the rotor blade. A substantially cylindrical surface that is formed in such a manner that the end of the protrusion touches the end of the protrusion of an adjacent rotor blade, and that the outer periphery formed by these protrusions is the entire circumference and surrounds the tip of the rotor blade. Form it so that it forms. Further, a dovetail groove extending from the working fluid inlet side of one rotor blade to the outlet side of the rotor blade located on the back side of the rotor blade is provided on the outer circumferential surface of the protrusion, and the dovetail groove is engaged with the rotor blade and the one rotor blade is engaged with the dovetail groove. Connecting pieces that connect the rotor blades and adjacent rotor blades are inserted one after another to connect all the blades around the entire circumference, but the connecting pieces are placed on the radially outer side of the cylindrical surface that forms the outer peripheral surface of the rotor blade. The rotor blade has a protruding blade portion, and the blade portion has the effect of pumping fluid from the downstream side to the upstream side of the rotor blade when the turbine rotates.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure is a perspective view of a portion near the tip of a rotor blade showing an embodiment of the present invention, and FIG. 2 is a plan view of the tip of the rotor blade viewed from the outer peripheral side in the radial direction. At the tip of one rotor blade 1a, a protrusion 2a extending toward the back side of the rotor blade and a protrusion portion 3a extending toward the return side are provided substantially perpendicularly to the longitudinal direction (radial direction) of the rotor blade. The end 4a of the protrusion 2a is in contact with the end 5b of the ventral protrusion 3b of the adjacent blade 1b located on the dorsal side of the rotor blade 1a, and the end 5a of the ventral protrusion 3a of the rotor blade 1a. teeth,
It is formed so as to be in contact with the end portion 4c of the dorsal projection 2c of the adjacent blade IC located on the ventral side of the rotor blade 1a. The outer circumferential surface 6 of the protrusion is formed to be a substantially cylindrical surface all around, forming a ring surrounding the tip of the rotor blade, and this ring allows the flow of fluid at the tip of the rotor blade to flow around the outer circumference of the tip of the rotor blade. Prevent leakage to the outside. Now, next, the outer circumferential surface of one protrusion 2c and the protrusion 3a that contacts this at the end is connected from the working fluid inlet side of the tip of the rotor blade 1c to the working fluid outlet side of the tip of the adjacent rotor blade 1a. An extending dovetail groove 7 is provided, and a connecting piece 8 having a cross-sectional shape that engages with the dovetail groove 7 is inserted in the direction of the groove to connect adjacent blades. On the other hand, in the state where the connecting piece 7 is inserted into the dovetail groove, the connecting piece 7 is connected to the second 0th order, which is formed to have a blade part 9 that protrudes radially outward from the outer peripheral surface 6 of the projections 2 and 3. To explain with a diagram, when a turbine rotor blade rotates in response to work by the working fluid, a flow is generated from the working fluid outlet side to the working fluid inlet side on the outer peripheral side of the tip of the rotor blade due to the blade portion 9 of the connecting piece 8. do. At this time, it is desirable to select a suitable airfoil shape for the shape of the vane portion 9 in order to pump the fluid from the working fluid outlet side to the inlet side.Generally, it is as shown in Figs. 1 and 2. The direction of warpage of the blade part 9 is 1
Although the shape is convex toward the working fluid outlet side, the pumping action occurs even without warpage. Now, the first step is to prevent fluid leakage between the outer circumferential side of the rotor blade tip and the outer circumferential wall. Explained by I. 4Im is a cross-sectional view taken along the line A-A in FIG. A gap 12 is provided to prevent movement, through which fluid leaks and flows from the inlet side to the outlet side of the moving blade 1.

This leakage flow is a flow that does not perform work and causes a decrease in turbine efficiency. However, due to the action of the blade part 9,
Since a flow is induced from the rotor blade outlet 12 side to the inlet side, a circulating flow as shown by the arrow 13 in FIG. This has the effect of preventing fluid from leaking from the rotor blade inlet side to the outlet side at the outer peripheral portion of the rotor blade tip. This leakage prevention effect improves turbine efficiency. In addition, since the blade part 9 is provided in the present invention, a braking effect is generated on the turbine rotation, and the shaft output is reduced compared to the case without the blade part 9. However, by optimizing the blade part shape, the above-mentioned effect can be achieved. The blade portion 9 can be driven with less power than the increase in shaft output due to efficiency improvement due to leakage prevention, and turbine efficiency can be improved.

Note that the blades provided on the upper part of the connecting piece 8 are limited to those having an airfoil shape, but as shown in FIG. It can exert a pumping effect.

Further, in the present invention, after the connecting piece 8 is inserted into the dovetail groove 7,
Although removal is prevented by appropriate means, it is also possible to adopt the structure shown in FIG. 6 as an example of removal prevention. That is, one end 13 of the dovetail groove 7 is closed by the protruding part 3, and after inserting the connecting piece 8 into the dovetail groove 7, the protruding part is closed by installing the wing ld shown by the two-dot chain line in the figure. 2
d can prevent the connecting pieces 8 from coming off, and in this way, it is possible to prevent the connecting pieces from coming off one after another.

During the assembly of this wing structure, the connecting piece 8 is prevented from being pulled out by other suitable means during the assembly of the last wing of the entire circumference.

Next, in the embodiment of the present invention, one connecting piece has been described as connecting only the tips of two adjacent rotor blades. As shown in the figure, it is possible to have a structure in which one connecting piece 8 connects three consecutive rotor blade tips, and furthermore, it is also possible to have a structure in which three or more rotor blade tips are connected. It is possible.

〔Effect of the invention〕

According to the present invention, it is possible to achieve a so-called full-circumference one-ring blade structure in which blades around the entire circumference of a turbine rotor blade are seamlessly connected at the tip thereof, and not only can a blade structure with excellent vibration characteristics be provided, but also Fluid leakage between the tip and the outer peripheral wall can be prevented, and the efficiency of the turbine can be improved.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a tip of a rotor blade according to an embodiment of the present invention, FIG. 2 is a plan view of a tip of a rotor blade of the present invention as viewed from the outer circumferential side, and FIG. 3 is a tip of a conventional rotor blade. FIG. 4 is a cross-sectional view showing the fluid flow between the tip of the rotor blade and the outer peripheral wall of the present invention in the direction of the ■-IV arrow in FIG. 2, and FIG. FIG. 6 is a perspective view of a portion of a rotor blade tip structure showing a modification of the invention. FIG. 7 is a plan view of the rotor blade tip section viewed from the outer peripheral side, showing another modification of the present invention. 7...Dovetail groove.

Claims (1)

[Scope of Claims] 1. A device for connecting the tips of turbine rotor blades, wherein protrusions are provided that extend toward the ventral side and the dorsal side of the rotor blades, respectively, in a direction substantially perpendicular to the longitudinal direction of the rotor blades. , an end of the protruding portion is formed so as to be in contact with an end of the protruding portion of the adjacent rotor blade, and an outer peripheral portion of the rotor blade formed by the protruding portion is formed to form a substantially cylindrical surface. Further, from the fluid inlet side of the rotor blade, on the outer circumferential surface of the protrusion of each of the rotor blades,
A dovetail groove extending to the fluid outlet side of the rotor blade adjacent to the back side of the rotor blade is provided, and connecting pieces that engage with the dovetail groove and connect the adjacent rotor blades are inserted one after another to completely In addition to seamlessly connecting all the blades around the circumference, the connecting piece includes a blade portion that protrudes toward the outer peripheral side in the radial direction than the outer peripheral surface of the protruding portion of the rotor blade, so that when the turbine rotates, the tip of the rotor blade What is claimed is: 1. A turbine rotor blade tip connection device, characterized in that it prevents fluid leakage between the blade and the outer circumferential wall.