JPH02112602A - Device for giving preload - Google Patents

Abstract

PURPOSE: To provide a pre-load with inexpensive means by inserting a shank made of a superplastic material, in which an expandable low-melting point material is packed, into a shank bore formed between a first and a second confronting notches formed in a turbine rotor disk and a turbine blade root. CONSTITUTION: A turbine rotor disk 10 is provided with a plurality of axially extending grooves 12 in its peripheral portion. A plurality of turbine blades 20 are mounted to the rotor disk 10 by fitting roots 22 in the grooves 12. A first notch 18 extending substantially parallel to a rotational axis of the rotor disk 10 is formed in a bottom of each of the grooves 12. On the other hand, a second confronting notch 22b is formed in the lowest portion of each root 22. A pre-load device 24 is inserted into a shank bore 25 formed between the notches 18, 22b. The pre-load device 24 comprises a shank 26 formed of a superplastic material. The shank 26 defines an interior chamber 28 filled with a low-melting point material 30 expandable due to the heating by a resistance heating material 32.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a preloading device for preloading the roots of turbine blades, and in particular to a preloading device suitable for use with rotor disks of turbomachines or axial flow turbines. It is related to.

[Tsunuki-Horimu 10% By forming multiple mounting grooves extending approximately in the axial direction on the rotor blade disk, and forming root portions with shapes corresponding to each of the turbine blades or blades, multiple mounting grooves are formed on the turbine rotor blade disk. It is well known in the art to install individual turbine blades. In this case, the root is slidably inserted into the mounting groove of the rotor disk and is provided with means for preventing axial movement. Typically, the mounting groove of the rotor disk and the root of the turbine blade are
Because they are shaped like a “Christmas tree” or “drumpet”, the mounting grooves and adjacent bearing surfaces formed at the roots are located in the radial direction of these elements, i.e., rotor discs and turbine blades. prevent movement. Another example of attaching a turbine blade to a turbine rotor disk employs a reverse installation procedure.

According to this reverse procedure, a generally axially extending groove is formed at the root of each turbine blade, while a protrusion or ridge is formed at the periphery of the rotor disk. In this case, the protrusion is axially slid onto the protruding part of the disc and means are provided to prevent axial movement.

The grooves in the protrusions and roots are also shaped in a Christmas tree or dome shape so that the clearly formed adjacent bearing surfaces of the protrusions and roots prevent radial movement between these elements. It looks like this.

However, as a practical matter, due to manufacturing tolerances of the elements, a certain amount of radial clearance or play remains between the bearing surfaces. These gaps allow slight radial movement of the turbine blades. When the turbine rotor disk reaches its stable operating speed, centrifugal force forces the bearing surfaces into contact with each other. During transient movements of the rotor disk, such as during startup and shutdown of the turbine, the turbine blade vibrates due to the gap between the root and the rotor disk. This is a highly undesirable characteristic and should be eliminated to maximize the useful life of the turbine blades and rotor disks.

The turbine blade roots and rotor disks are designed to accommodate assembly gaps and bring the bearing surfaces into contact during transient motions or when the rotor disks are completely stationary. Devices have been proposed that apply a preload force between grooves. Typically,
This type of device consists of an elastic bottle inserted between the bottom of the turbine blade root and the groove of the rotor disk.

- Once installed, the expansion of the device exerts an approximately radially outward force on the bottom of the turbine blade root, so that the bearing surface of the turbine blade root is formed in the groove of the rotor disk. is brought into contact with the corresponding bearing surface.

Although this type of device has generally been found to work satisfactorily, special tools are required to insert the elastic bottle. Also, in order to make the individual turbine blades replaceable, special tools must be provided to accommodate and remove the inserted elastic bins.

Additionally, it is often necessary to drill or cut the elastomeric bottle in order to remove it from the rotor disk assembly.

It is also known to provide a cam device between the root of the turbine blade and the rotary blade disc groove to apply a preload force. These cam devices, which can be combined with torsion springs,
Adds complexity to the rotor disc assembly and increases manufacturing and maintenance costs.

Furthermore, it is also known to axially lock the prong in the groove of the rotor disk by means of a pin having a fixed head portion at one end and a deformable or removable head portion at the other end. ing. These head portions abut axially facing surfaces of the rotor disk and root to prevent relative axial movement between the rotor disk and the root.

The present invention relates to a preload force application device which alleviates the disadvantages of known devices.The device according to the invention does not require any special tools for use, is easy to install and remove, and is rotatable. It does not increase the complexity of the wing disc assembly.

The device according to the invention is made of a superplastic material that can be inserted axially into a shaft hole formed by first and second mutually opposed notches formed in a turbine rotor disk and a turbine blade root. and a shaft portion by which the stem portion is attached to the rotor disk.

In one embodiment of the present invention, the first notch is formed at the base of the mounting groove formed in the turbine rotor disk, and the second notch opposite thereto is formed at the bottom of the root part. The axial bore formed in the inner part and thus defined by the recesses extends approximately parallel to the axis of rotation of the rotor disk.

In another embodiment of the invention, the first notch is formed in a groove in the upper surface of a protrusion formed in the turbine rotor disk, and the second, opposing notch is formed in a groove in the upper surface of the protrusion formed in the turbine rotor disk. Axial holes formed in certain mounting grooves and defined by these notches extend in a direction generally transverse to the axis of rotation of the rotor disk.

The shank defines an interior chamber in which a low melting point material is placed. An electrical resistance heating element is disposed within the low melting point material and has means for connecting to an external power source. The apparatus also includes a head portion attached to each end of the shaft, each head portion abutting an axially facing surface of the rotor disk and root, thereby attaching the head portion. At times, relative axial movement between these elements, the rotor disk and the root, is prevented.

The shaft portion is dimensioned to be easily inserted into the shaft hole formed by the first and second notches. If it is desired to preload the wing root, electrical energy is supplied to the electrical resistance heating element to increase its temperature and the temperature of the low melting point material. The low melting point material expands, thereby causing the superplastic material forming the shank to expand. The radial expansion of the cylindrical shaft exerts a radially outward force on the root of the blade, thereby bringing the bearing surface of the root into contact with the corresponding bearing surface of the rotor disk. , to absorb gaps between these bearing surfaces.

The invention will be more easily understood from the following description of a preferred embodiment, shown by way of example only in the accompanying drawings, in which: FIG.

FIGS. 1 and 2 show a portion of an embodiment of a turbine rotor disk 10 having a plurality of substantially axially extending grooves 12 formed around its periphery.

Each groove 12 extends axially substantially parallel to the axis of rotation (not shown) of the rotor disk 10. In known manner, each of the grooves 12 is defined by sides 14 and 16, respectively, on which a plurality of bearing surfaces 14a and leas are formed. Further, at the base of each groove 12, a rotor disk 1 is provided.
a first notch 1 extending substantially parallel to the axis of rotation of
8 is formed.

A plurality of turbine blades 20, each having a root 22, are attached to the rotor disk 10 by sliding the root 22 axially into each groove 12.

A second bearing surface 22a is formed at the root portion 22,
The bearing surfaces 22a abut respective bearing surfaces 14a and 16a in stable operating conditions of the rotor disk. To accommodate the sliding movement of the root 22 relative to the groove 12, and due to normal manufacturing tolerances of the rotor disk 10 and the root 22, the bearing surfaces 22a and 14a, l
There is a gap of the amount between ea and ea.

a first notch 18 and a second opposing notch 22b defined at the lowest portion of each root 22 to inhibit vibration of the turbine blade during transient operating conditions of the rotor disk assembly; A preload force applying device 24 is inserted into the shaft hole 25 formed by. As shown in FIG. 2, the shaft portion 26 of the application device 24 is formed in a size that allows it to easily slide between the opposing notches 18 and 22b.

As best shown in FIG. 4, the shaft 26 defines an interior chamber 28 that is filled with a low melting point material 30. As used herein, the term "low melting point material" refers to a material having a melting point of about 94°C to 538°C (200"F to 1
000° F.) and below the melting point of the superplastic material of the shank 28. Examples of such low melting point materials include tin-lead solder alloys or eutectic mixtures (
eutectics), silver-copper eutectic mixtures, other alloys such as yttrium, bismuth or beryllium alloys, and related eutectic mixtures with desired melting points. A resistive heating element 32 or other heating means extends into the low melting point material 30 and
It is electrically connected to a threaded boss 34. The boss 34 has a head portion 34 a that is screwed into one end of the shaft portion 26 and abuts against the root portion 22 and the surface of the rotor disk 10 facing in the axial direction. The interior chamber 28, the low melting point material 30 and the resistive heating element 32 described above constitute an expandable means for expanding the superplastic material of the shank 26.

A second head 36 is threaded onto the opposite end of the shaft 26 and defines a head portion that abuts the root 2 and the axially facing surface of the rotor disk 10. .

As can be seen, once boss 34 and head 36 are engaged with either end of shaft 26, relative axial movement between root 22 and rotor disk 10 is prevented.

The shaft portion 26 is formed from a superplastic material. The superplastic material may be a hypereutectoid nickel-chromium alloy capable of plastic deformation of at least 500%. Examples of other superplastic materials that can be used include alloys such as:
It is not limited to these.

1) Nickel-chromium Kh 20 N802) Nickel modified titanium 6 aluminum 4 vanadium 3) Zinc-aluminum 4) Nickel 75% boron 17% silicon 8% 5)
Aluminum-Copper Eutectic Mixture 6) ZhS6U-Refractory Alloy If it is desired to preload the root 22, connect the resistive heating element 32 to a power source to increase the temperature of the resistive heating element 32. The increased temperature of the resistive heating element 32 causes the low melting point material 30 to expand, thereby causing a similar expansion in the shaft 26. Most of the expansion occurs in the radial direction, thereby absorbing the gap between bearing surfaces 22a and 14a, lea, and acting to bring them into contact with each other, as shown in FIG. do. The preload prevents vibration or movement between the turbine blades and the rotor disk during transient operating conditions of the rotor disk assembly. Base part 2
2 and the rotor disk 10 each have a locking notch 38.
and 40 may be formed.

5 and 6 show a portion of another embodiment of a turbine rotor disk 10 having a circumferentially extending protrusion 41 formed at its periphery. The protrusion 41 extends in a direction substantially transverse to the rotational axis (not shown) of the rotor disk 10. Each of the protrusions 41 has a plurality of bearing surfaces 42 .
It is defined by sides 42 and 44, which are formed with a and 44a. A first notch 46 is formed in the upper surface 48 of the protrusion 41 and extends in a direction substantially transverse to the axis of rotation of the rotor disk 10 .

A plurality of turbine blades 20 are provided, each turbine blade having a root portion 50, and the root portion 50 is connected to the rotor disk 1.
A mounting groove 52 extending in a direction substantially transverse to the rotation axis of
have. Each of the mounting grooves 52 is defined by sides 54 and 56 having bearing surfaces 54a and 56a formed therein, respectively. Each installation? The base of 1I52 has a second notch 58 formed at the base. The preload force applying device 24 is connected to the first notch 4 of the protrusion 41.
6 and the wing root attachment are inserted into the shaft hole 25 formed by the second notch 58 of the groove 52, and are sized to be slidable between the opposing notches 46 and 58. In this embodiment, the last turbine blade is designed to close in the conventional manner on the protrusion of the rotor disk, so that no stress reduction or expansion tubes are provided. The opening for the last turbine blade accommodates electrical connections for a resistive heating element 32 of low melting point material 30 and means for maintaining proper attachment and alignment to the last turbine blade. After expansion of the shank 26 of superplastic material, the last turbine blade is assembled into position.

The above description has been made for illustrative purposes only and is not to be construed as limiting the invention in any way.

[Brief explanation of the drawing]

FIG. 1 is a partial perspective view showing an embodiment of an axial flow turbine rotor equipped with a preload force applying device according to the present invention, and FIG. 2 is an assembly of the applying device in the embodiment of FIG. 1 according to the present invention. FIG. 3 is a partially exploded perspective view showing the embodiment of FIG. 1, and FIG. , a partial sectional view along the ■-1%' line in Fig. 3, and Fig. 5,
FIG. 6 is a partially exploded perspective view of another embodiment of an axial turbine rotor equipped with a preload force applying device according to the present invention.
FIG. 6 is a partial cross-sectional view showing the application device according to the invention provided between the rotor blade disk protrusion and the turbine blade root of the embodiment of FIG. 5; 10...Turbine rotor blade disk 22.50...Turbine blade root 24...Preload force applying device 25...Shaft hole 26...Shaft portion 28...Inner chamber (expandable Means) 30...Low melting point material (expandable means) 32...Resistance heating element (expandable means) Applicant: Westinghouse Electric Corporation"■ FIG, 4

Claims (1)

[Scope of Claims] A device for applying a preload force between a turbine rotor blade disk and a turbine blade root attached to the turbine rotor blade disk, the device comprising: (a) the turbine blade root; (b) a shank formed of a superplastic material insertable into an axial hole defined between the turbine blade disk and the turbine rotor disk; an expandable means for applying a preload force to the root of the turbine blade;