RU2225522C2 - Gas-turbine engine behind-the-compressor labyrinth seal - Google Patents

Abstract

FIELD: mechanical engineering; gas-turbine engines of ground and aircraft application. SUBSTANCE: according to invention, in proposed behind-the compressor labyrinth seal of gasturbine engine containing two-tier labyrinth with sealing lips installed on shaft and mating stator flange, sealing lip of each tier of labyrinth extreme from compressor rotor is made of increased thickness at H/h=1.5-3, where H is thickness of extreme lip; h is thickness of other lips. Working surfaces of sealing lips of inner tier of labyrinth are made to generatrix of cone with angle of tilting of 0.5^o - 3^o towards side of outlet from labyrinth, and number of lips of outer tier of labyrinth is 1.5-5 times greater than number of lips on inner tier labyrinth. EFFECT: improved reliability in operation owing to reduction of thermal stresses and increase of vibration stability in seal lips, reduced wear. 2 dwg

Description

 The invention relates to the field of engine development of ground and aviation applications.

 Known air labyrinth seal, consisting of a rotating labyrinth with combs and a reciprocal stator flange mounted on a stator [1].

 The disadvantages of the known design are increased air leakage due to the small number of sealing scallops and reduced reliability due to the possibility of cracking the last downstream scallop maze and breakage of the rotating labyrinth.

 Closest to the claimed is a sealing device behind the compressor of a turbojet dual-circuit engine, consisting of a multi-tier labyrinth connected to the motor shaft, and a stator flank reciprocal to it. An annular radial rib is made on the inner tier of the labyrinth for the installation of balancing weights [2].

 A disadvantage of the known design is low reliability due to the possibility of cracking the last labyrinth scallop on each tier of the labyrinth, as well as the wear of the labyrinth scallops on the inner tier of the labyrinth due to its elastic deformation under the influence of centrifugal force from balancing weights.

To minimize the elastic deformation of the inner tier of the labyrinth, the optimal number of ridges of the labyrinth seal (Z ₂ ) located on it is also important.

With a small Z _{2, the} sealing properties of the labyrinth seal deteriorate, and with an excessively large one, the elastic deformation and wear of the combs of the lower tier of the labyrinth seal increase. This is due to the fact that the inner tier of the labyrinth is cantilevered with respect to the canvas of the labyrinth, and with a large extension of the cantilever (i.e., with a large number of combs Z ₂ ), the inner tier is deformed by centrifugal forces.

 The technical problem that the invention solves is to increase the reliability by reducing thermal stresses and increasing vibration resistance in the combs of the seal, as well as eliminating its wear.

 The essence of the invention lies in the fact that in the compressor labyrinth seal of a gas turbine engine containing a two-tier labyrinth mounted on the shaft with sealing ridges and a stator flange corresponding to it, according to the invention, the sealing comb of the labyrinth extreme from the compressor rotor is thickened, and H / = 5 ... 3, where H is the thickness of the extreme scallop; h is the thickness of the remaining combs.

The working surfaces of the sealing ridges of the inner tier of the labyrinth are made along the generatrix of the cone with an angle of inclination of 0.5-3 ^o in the direction of exit from the seal, while the number of ridges on the outer tier of the labyrinth exceeds the number of ridges in the inner tier of the labyrinth by 1.5 ... 5 times .

 The thicker combs of the labyrinth tier, which are extreme from the compressor rotor, are thickened due to the fact that at each tier they experience increased thermal stresses in transient conditions and acoustic vibratory stresses, because in a labyrinth seal, the maximum velocities of the compacted working fluid (air) are realized on the last flowing labyrinth scallop.

 Thickened scallops have improved heat transfer from the top of the scallop to its base, which reduces thermal stresses in them during transient conditions, as well as increased vibration resistance.

 This is especially important for pressurized labyrinth seals, as modern compressors to increase engine efficiency are performed with a high compression ratio of 20 ... 35, and therefore, at the exit from each tier of the labyrinth seal, high supersonic speeds of the compacted working medium are realized.

 The ratio of the thickness of the extreme scallop N along the flow of the compacted body to the thickness of the remaining scallops h is 1.5 ... 3.

 At H / h <1.5, cracking of the extreme scallop is possible due to acoustic vibrations of the working fluid arising during engine operation.

 At H / h> 5, there is a high probability of cracking preceding the extreme scallop due to thermal stresses arising from low heat transfer from the periphery of the sealing scallop to its base.

The working surfaces of the sealing ridges of the inner tier of the labyrinth must be carried out along the generatrix of the cone with an angle of inclination α = 0.5-3 ^° in the direction of exit from the seal to avoid excessive cutting of the ridges into the stator flange and wear of the labyrinth seal.

Moreover, in the case when α <0.5 ^° , the seal may deteriorate due to excessive cutting of the combs into the stator flange reciprocal to them, especially at the maximum engine operating mode.

If α> 3 ^° , then the seal may deteriorate, especially in intermediate and transient engine operation, due to excessive disclosure of the radial clearance between the stator and rotor.

Since the inner tier of the two-tier labyrinth is made in the form of an annular rib cantilever relative to the maze web, the ratio of the number of scallops Z ₁ on the outer tier of the labyrinth and the number of scallops on the inner tier of the labyrinth Z ₂ should be optimal.

If Z ₁ / Z ₂ <1.5, then due to excessive radial deformation of the inner tier of the labyrinth, wear of the sealing ridges of the labyrinth will occur.

When Z ₁ / Z ₂ > 5, the effectiveness of the labyrinth seal decreases.

 The invention is illustrated as follows.

 In FIG. 1 shows a longitudinal section of the inventive seal, figure 2 - element I in figure 1 in an enlarged view.

 The compressor labyrinth seal 1 of the gas turbine engine consists of a two-stage compressor labyrinth 2 and a reciprocal stator flange 3 mounted on the support 4 of the angular contact ball bearing 5, and serves to seal the high pressure cavity 6 behind the last working blade 7 of the compressor from the low pressure compressor discharge cavity 8 .

 The two-tier compressor maze 2 is installed with slots 9 on the splined shaft 10 and mounted on the disk of the last stage 11 of the compressor using a bayonet connection 12, which is made on the outer tier 13 of the maze 2.

 On the outer surfaces 14, 15 of the outer tier 13 and the inner tier 16 of the labyrinth 2, sealing combs 17 are made of thickness h and the outer combs 19 of the thickness of the working fluid (air) 18, which are extreme for each tier, are sealed by comb 18.

The inner tier 16 of the two-tier labyrinth 2 is made in the form of an annular rib 20 located cantilever relative to the canvas 21 of the labyrinth. The axial length of this rib 20 and, therefore, the ratio of the number Z _{2 of} scallops 17, 19 on this tier and the number of scallops Z ₁ on the outer tier are chosen optimal in order to exclude radial plastic deformation of the rib 20 at maximum engine operating conditions.

To balance the compressor rotor 22, a radial rib 23 is made on the inner side of the annular rib 20, on which balancing weights 24 are mounted, under the action of centrifugal forces from which, when the engine is running, the annular rib 20 is elastically damped in the radial direction, which leads to excessive cutting of the scallops 17 and 19 into the stationary flange 3. To exclude such a cut-in, the working surfaces of 25 combs 17 and 19 of the inner tier 16 of the labyrinth 2 are made along a generatrix of the cone with an angle of inclination α = 0.5-3 ^° towards the exit from the seal 1.

 The inventive device operates as follows.

 When the engine is running, high-pressure air from the cavity 8 behind the last rotor blade 7 of the compressor rotor 22 tends to flow into the low pressure compressor unloading cavity 8. In this case, at the extreme sealing ridges 19 of each of the tiers 13, 16 of the two-tier labyrinth 2, supersonic speeds of the compressed stream 18 arise which may cause them to crack and break.

 However, since the combs 19 are made with an increased thickness H, the formation of cracks and breaks in the combs 19 does not occur.

Sources of information
1. G.S. Skubachevsky. Aircraft gas turbine engines. Design and calculation of parts. M.: Engineering, 1981, p. 98, Fig. 3.43a.

 2. RF patent 2036312, F 01 D 11/02, 1995.

Claims (1)

A compressor labyrinth seal of a gas turbine engine containing a two-tier labyrinth mounted on a shaft with sealing ridges and a stator flange reciprocal to it, characterized in that the sealing comb of the labyrinth tier, which is the outermost from the compressor rotor, is thickened, moreover, N / h = 1.5 ... 3, where H is the thickness of the extreme scallop; h is the thickness of the remaining scallops, the working surfaces of the sealing ridges of the inner tier of the maze are made along a generatrix of the cone with an angle of inclination of 0.5-3 ° in the direction of exit from the seal, while the number of scallops on the outer tier of the labyrinth exceeds the number of scallops on the inner tier of the maze 5 ... 5 times.

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