RU2472981C1 - Bolted joint of rotating parts - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: bolted joint of rotating parts combined in a pack with holes arranged in a circumferential direction inside of which there are sleeves installed to the height of parts pack with coupling-bolts arranged in their central holes. Each hole is of oval shape and it is elongated in circumferential direction, and sleeve is with oval section elongated in circumferential direction. At that b/a=1.36-1.5; 0(2.5-3)×b, where a is size of sleeve section in radial direction; b is size of sleeve section in circumferential direction; c is length of circumference between central holes of adjacent sleeves.

EFFECT: increasing cyclic life and reliability of bolted joint of rotating parts under high working parameters by means of relief of stress concentration zones in mentioned parts.

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Description

The invention relates to the field of mechanical engineering and aircraft engine construction, can be used to connect the rotating parts of the rotor of a gas turbine engine of aviation and ground applications.

A bolted connection is known, including a cylindrical unloading sleeve with a circular cross section, which is used for centering and unloading the bolt, reducing shear stresses in the bolt itself and eliminating shear deformations in the connected parts (Atlas. Machine parts. V.N. Bykov, S.P. Fadeev , Higher School Publishing House, 1969, p. 83, Fig. 3.4). When parts rotate around bolt holes, stresses occur. The presence of a stress concentrator, which increases the level of acting stresses by a factor of 3-4, is the main disadvantage of this design, which reduces the cyclic durability and resource of parts.

In the aircraft engine industry, the connection of parts using tie bolts is widely used. Holes for bolts, which are stress concentrators, can be located in the blade web and on the external flanges of the parts. Remote flanges are used to remove the hub in the form of an opening from the disk web.

The presence of a stress concentrator - a round bolt hole, which increases the level of acting stresses by 3-4 times and reduces the resource of parts, is the main disadvantage of this design.

In practice, this problem is solved by performing fillets of the "crown" type in the flanges, which ensures sufficient unloading of the holes. The effectiveness of such refinement of parts is confirmed by tests and is widely used, for example, in flanges for balancing weights of labyrinths of the disk of the 13th stage of the high-pressure compressor rotor (HPC) of the PS-90A, PS-90A2 engines (A.A. Inozemtsev, M.A. Nikhamkin , VL Sandratsky, Fundamentals of Designing Aircraft Engines and Power Plants, Volume 4, p. 109).

Closest to the claimed design of the connection is the connection node, comprising a package of parts, a cylindrical sleeve and a bolt with a nut. Round holes are made in the details (RF Patent No. 2263828, F16B 5/02, 2005).

A disadvantage of the known site is the round shape of the holes for the sleeve, causing increased stresses in the bolt and in the connected parts, reducing the cyclic life and reliability of the bolted connection during rotation of the parts.

The technical problem solved by the invention is to increase the cyclic life and reliability of the bolted connection of rotating parts at high operating parameters by unloading the zones of stress concentration in these parts.

The essence of the invention lies in the fact that in the bolted connection of rotating parts, combined in a package, with holes located around the circumference, inside of which, to the height of the package of parts, bushings are installed with coupling bolts located in their central holes, according to claim 1, each hole is made oval in shape and elongated in the circumferential direction, and the sleeve with an oval section elongated in the circumferential direction, while

b / a = 1.36-1.5; c> (2.5-3) × b,

where a is the size of the cross section of the sleeve in the radial direction;

b is the cross-sectional dimension of the sleeve in the circumferential direction;

C is the circumference between the Central holes of adjacent bushings.

In addition, according to claim 2 of the formula, in order to ensure the isolation of the cavities of the compressor stages and to maintain the necessary contact area between the parts and the bolt, the following ratio must be observed:

(a-d) / 2> 1.4 mm,

where d is the diameter of the hole of the sleeve for the bolt.

The configuration of the sleeve and the dimensions of the holes for it are selected on the basis of analysis of the geometry of the disks and calculations of the stress-strain state.

It was found that the implementation of the holes are oval, elongated in the circumferential direction, and the execution of the sleeve with the corresponding oval with the ratios:

b / a = 1.36-1.5; c> (2.5-3) × b,

allows you to efficiently unload stress concentration zones and increase the calculated values of the cyclic resource of parts, estimated from the conditional low-cycle fatigue curve for disk alloys (Technical Report No. 12045, M., TsIAM, 1993. Development of an aviation gas turbine engine resource management technique to increase strength reliability, increase resources and cost reduction during life tests (in relation to the PS-90A engine and its modifications)).

Bushings with an oval cross-section perform the following functions in the claimed design:

- provide fixation of parts relative to each other;

- maintain the necessary contact area between the flanges and the standard round bolt;

- provide isolation of the cavities of the sections (steps) of the compressor.

In addition, the use of bushings of the claimed design simplifies the process of assembling compressor parts, and in the manufacture of bushings of lightweight and durable material, it allows to reduce the mass of disk flanges and the entire rotor as a whole.

Analysis of the calculation results shows that the claimed bolted connection has the prospect of use in modern engines of the latest generation.

If b / a <1.36, the shape of the hole tends to circle, the level of circumferential stresses in the holes of the connected parts increases, therefore, the cyclic durability decreases.

If b / a> 1.5, the hole is more elongated in the circumferential direction, while reducing the area of the cylindrical section of the mating parts, which increases the risk of loss of bearing capacity, increases the level of radial stresses and reduces cyclic durability.

If с≤2.5b, the distance between the centers of the holes decreases, the area of the cylindrical section of the connected parts decreases proportionally, which increases the risk of loss of bearing capacity.

The ratio c> 3b leads to the fact that the distance between the centers of the holes is increased, the lines of action of the circumferential stresses are aligned, and the effect of reducing the concentration of stresses decreases.

In addition, according to claim 2, in order to maintain the necessary contact area between the parts and the bolt, as well as for technological reasons, it is necessary to observe the following ratio: (a-d) / 2> 1.4 mm. Otherwise, there are technological difficulties with the manufacture of the sleeve, because The wall thickness of the sleeve is too small. In addition, unacceptably high voltages occur in the thin wall of the sleeve.

Thus, at high operating parameters, the use of this design of the bolted connection makes it possible not only to equalize the stresses along the thickness of the package of parts and in the bolts, but also to significantly reduce the level of acting stresses in the connected parts, increasing their service life.

In Fig.1 shows a cross section of the package of connected parts with a sleeve having an oval section, in Fig.2 - section aa in Fig.1. Figure 3 shows a bolted connection in the assembly of parts of the rotor of the HPC in a perspective view.

A bolted connection includes a package of rotating parts for a gas turbine engine (GTE), for example, flange 1 of a disk of the first stage (KVD), flange 2 of the shaft of the KVD and disk 3 of the second stage of the KVD. In parts 1, 2, 3, oval holes 4 are made, elongated in the circumferential direction under the sleeve 5 with the same oval section and dimensions a and b in the radial and circumferential directions, respectively. In the hole 4, the sleeve 5 is placed over the entire thickness of the package of parts 1, 2, 3. In the sleeve 5 there is a round central hole 6 of diameter d for a standard round-neck coupling bolt 7. The diameter of the bolt head 7 and the outer diameter of the nut 8 overlap during assembly the radial dimension of the sleeve 5, subject to the conditions

(a-d) / 2> 1.4 mm.

The sleeve 5 provides isolation of the cavities of the compressor stages, maintains the necessary contact area between the flanges and the coupling bolt 7.

The holes 6 are evenly spaced along the entire circumference of the parts 1, 2, 3 to be connected, while the circumference C between them depends on the size of the section b of the sleeve 5 in the circumferential direction.

The bolted connection is collected as follows.

A sleeve 5 is inserted into the oval hole 4 of the package of rotating parts 1, 2, 3, in which a standard bolt 7 is placed and secured with a nut 8. During the operation of the HPC, the stress concentration in the area of the holes 4 in the blade and in the flanges 1 of the disks will be minimal, which allows work at high preset engine parameters, increasing the cyclic life and reliability of the bolted connection.

Claims (2)

1. Bolted connection of rotating parts, combined in a package, with holes located around the circumference, inside of which, to the height of the package of parts, bushings are installed with coupling bolts located in their central holes, characterized in that each hole is oval and elongated in the circumferential direction, and sleeve - with an oval cross section elongated in the circumferential direction, with b / a = 1.36-1.5; c> (2.5-3) b
where a is the size of the cross section of the sleeve in the radial direction;
b is the cross-sectional dimension of the sleeve in the circumferential direction;
C is the circumference between the Central holes of adjacent bushings. 2. Bolt connection of rotating parts according to claim 1, characterized in that (a-d) / 2> 1.4 mm, where d is the diameter of the bore of the sleeve for the bolt.

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