CN113685234B

CN113685234B - Labyrinth sealing device based on hedging principle

Info

Publication number: CN113685234B
Application number: CN202111013691.5A
Authority: CN
Inventors: 刘传凯; 丁水汀; 王家俊; 王傲; 邱天
Original assignee: Beihang University
Current assignee: Beihang University
Priority date: 2021-08-31
Filing date: 2021-08-31
Publication date: 2022-08-09
Anticipated expiration: 2041-08-31
Also published as: CN113685234A

Abstract

The invention discloses a labyrinth sealing device based on a hedging principle. The device is composed of a rotor (a grate disc) and a stator (a lining), wherein the grate disc comprises at least two step teeth, the lining corresponding to the step teeth is step-shaped, and an inward concave annular counter-flushing groove is additionally arranged at the tail end of each step. Compared with the conventional labyrinth sealing structure, the labyrinth sealing structure has the advantages that the leakage amount can be reduced and the sealing capability can be improved under the same working condition of the aero-engine, and the sealing effect is gradually increased along with the increase of the rightward axial displacement of the rotor within a certain axial displacement range.

Description

Labyrinth sealing device based on hedging principle

Technical Field

The invention relates to the field of aeroengine sealing, in particular to a labyrinth sealing device based on a hedging principle.

Background

The labyrinth seal is an effective non-contact seal structure widely used in aircraft engines. The labyrinth seal has the advantages of simple structure, long service life, easy maintenance and high reliability at high temperature and high rotating speed, is generally applied to various structures of an aero-engine, such as the seal of a gas path between a gas compressor and a turbine, the seal of rim gas, the seal of internal flow air, the seal of lubricating oil in a main bearing lubricating oil seal system and the like, and the seal quality of the labyrinth seal controls the distribution of air flow on the whole engine cooling network to a great extent, thereby directly influencing the efficiency and the reliability of the engine. The efficiency and the performance of the engine can be directly reduced when the sealing leakage flow of the labyrinth is larger than a designed value, the air flow is obviously heated and the thermal expansion of the rotor is increased when the sealing leakage flow of the labyrinth is too small, and the service life of the engine is shortened. Therefore, the design of the labyrinth capable of improving the sealing effect has important significance for improving the performance of the aero-engine.

The traditional stepped labyrinth is a non-contact dynamic sealing structure and comprises a labyrinth disc 1 (a rotor) and a stepped bushing 2 (a stator) as shown in figure 1. More than 2 grid teeth 3 are arranged on the grid toothed disc 1 along the axial direction, and the height difference exists among the heights of all the grid teeth 3 along the axial direction of the grid toothed disc 1 and the grid teeth are distributed in a step shape; a tooth cavity 4 is formed between two adjacent grid teeth 3. The stepped bushing 2 is a sealing bushing sleeved outside the labyrinth plate 1, the side wall of the stepped bushing is axially stepped and is matched with the height difference of each labyrinth 3 in the axial direction of the labyrinth plate 2, the circumferential side wall of each step corresponds to the tooth top of one labyrinth 3, and a gap is reserved between the tooth top of each labyrinth 3 and the corresponding step side wall. When the airflow passes through the gap between the two, the airflow is throttled and accelerated to generate a jet flow area, a part of pressure energy is converted into kinetic energy, the airflow collides on the inner wall of the stepped bushing 2 to generate a backflow area, and a larger backflow area is generated at the lower part of the tooth chamber 4 due to the structure of the tooth chamber 4. Due to the existence of the backflow areas, the kinetic energy of the airflow is converted into heat energy under the action of turbulent flow and viscous dissipation and is consumed, and finally, the sealing effect is achieved.

For the step labyrinth, the sealing function is mainly realized by virtue of the throttling effect at the tooth top and the eddy current dissipation between tooth cavities. When the jet flow impacts the lining part, stagnation is formed, vortex is formed due to shearing action, and when the axial displacement in the positive direction is large, throttling is formed between the jet flow and the lining, so that the flow coefficient is further reduced.

Disclosure of Invention

The invention provides a hedge principle-based labyrinth sealing structure capable of improving the sealing effect, and aims to solve the problems that the existing stepped labyrinth sealing effect of an aero-engine is limited, the sealing effect is easy to lose, and the safety is low.

The invention relates to a grate sealing device based on a hedging principle, which comprises a grate plate, step grates axially designed on the grate plate and step bushings matched with the step grates.

In the step bushing, each step is provided with a step side wall and a step tail end face, and the step tail end face is provided with an inwards concave arc opposite punching groove. Therefore, when air flow passes through the tooth top of the comb tooth, one side of the nearly stepped bushing flows through the tooth top of the comb tooth at a high speed due to relatively small resistance, and flows into the circular arc opposite punching groove along the wall surface of the stepped bushing, a clockwise vortex is formed under the influence on the punching groove, the circular arc opposite punching groove is reversely punched at a high speed at the notch of the circular arc opposite punching groove, and the opposite punching is formed by the jet flow between the circular arc opposite punching groove and the original tooth.

The invention has the advantages that:

1. according to the grate sealing device based on the hedging principle, the inward concave annular hedging groove is additionally formed in each step of the step bushing, so that airflow is jetted into the hedging groove along the wall surface, a clockwise vortex is formed under the influence of the hedging groove, the counter-punching is performed at the groove opening at a high speed, the counter-punching is performed with the jet flow between the groove opening and the original teeth, the ventilation effect of the grate is reduced, and the purpose of sealing optimization is achieved;

2. according to the grate sealing device based on the hedging principle, the right-size hedging groove space enables dissipation vortex behind the teeth to be fully developed, and the dissipation of energy is further intensified;

3. according to the grate sealing device based on the hedging principle, through the design of the hedging groove, the contact between airflow and the wall surface is increased, and the viscous shear dissipation is also increased to a certain extent; under the condition of a larger radial clearance, the energy dissipation is larger and the sealing effect is more obvious due to the formation of the opposite impact vortex.

4. The grate sealing device based on the hedging principle has the advantages that when the gap of the grate changes, the sensitivity to the gap change is low, and the stability is higher.

Drawings

Fig. 1 is a schematic view of a conventional stepped inclined grate structure and a flow field.

Fig. 2 is a schematic view of the structure and flow field of the labyrinth sealing device based on the hedging principle.

Fig. 3 is a partially enlarged schematic view of each stage of step in the grate sealing device based on the hedging principle.

FIG. 4 is a schematic structural view of a trapezoidal hedging slot of the grate sealing device based on the hedging principle;

FIG. 5 is a schematic structural view of an inverted trapezoidal hedging slot of the grate sealing device based on the hedging principle;

fig. 6 is a graph comparing the sealing effect of the grate sealing device of the invention obtained by simulation and the traditional stepped inclined grate structure under the same condition.

In the figure:

1-grate disc 2-stepped bush 3-grate

4-tooth cavity 5-step side 6-arc opposite impact surface

7-step end face

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings.

The invention relates to a labyrinth sealing device based on the hedging principle, which improves a stepped bushing 2 for a transmission stepped labyrinth and designs that each step in the stepped bushing 2 is provided with a step side surface 5, a hedging surface 6 and a step tail end surface 7, as shown in figures 2 and 3.

Wherein, the side surface 5 of the step is a surface opposite to the tooth top of the comb tooth 3; the tail end surface 7 of the step is a surface facing the tail end of the grate plate 2; two opposite side edges of the step side 5 are a side A edge and a side B edge; the two opposite sides of the step end face 7 are respectively an end face A side and an end face B side. The side A of the current ith step is connected with the side B of the end face of the i-1 th step; the side B edge of the current i-th step is connected with the side A edge of the tail end surface of the i-th step through the arc hedging surface 6; the straight edges of two opposite sides of the arc opposite punching surface 6 are respectively a straight edge A and a straight edge B, the straight edge A is connected with the edge of the tail end surface A, and the straight edge B is connected with the edge of the side surface B, so that an inward concave arc opposite punching groove is formed on the outer side of the tail end surface of the step.

In the labyrinth sealing device with the structure, the labyrinth plate 1 comprises at least two grates 3, each grate 3 has the same shape, and the distances between the adjacent grates 3 are equal; and the radial distance between the step side 5 of each step and the corresponding tooth top of the comb tooth 3 is equal.

As shown in fig. 3, the stepped bushing 2 of the above structure also has the following features simultaneously:

a. the step side surface 5 is tangent to the arc hedging surface 6;

b. one end of the step side face 5, which is connected with the arc hedging face 6, is inclined outwards, so that the step side face 5 and the grate disc 2 form an included angle of 6-10 degrees in the axial direction.

c. The central angle gamma of the circular arc opposite impact surface 6 is designed to be 180-240 degrees;

d. the included angle alpha between the step side surface 5 of the i-th step and the step tail end surface 7 of the i-1-th step is designed to be 70-105 degrees.

In order to achieve a better sealing effect, the end face of each step is designed to be lower than the side face B, namely to be closer to the corresponding grate 3 of the step, and the radius Ra of the circular arc hedging surface 6 and the radial width a of the end face of the step need to satisfy 2Ra > a.

The invention relates to a labyrinth sealing device based on the hedging principle, wherein an inward-concave arc hedging groove is additionally arranged at each step. When the airflow passes through the top of the comb teeth 3, one side close to the stepped bushing 2 flows through the top of the comb teeth 3 at a high speed due to relatively small resistance, and the airflow is jetted into the arc opposite punching groove along the wall surface of the stepped bushing 2 to form a clockwise vortex under the influence of the punching groove, is reversely punched at the notch of the arc opposite punching groove at a high speed, forms opposite punching with the jet flow between the original teeth, reduces the ventilation effect of the comb teeth and achieves the purpose of sealing optimization; meanwhile, the opposite-punching slot space with proper size enables dissipation vortex behind the teeth to be fully developed, and further enhances the dissipation of energy; in addition, the present invention increases the contact of the air stream with the wall surface and also increases the viscous shear dissipation to some extent.

The shape of the concave annular counter-flushing groove added at each step based on the counter-flushing principle can be annular, can also be designed into a trapezoidal groove, an inverted trapezoidal groove and the like, as shown in fig. 4 and 5, wherein geometric parameters such as the depth, the angle, the shape and the like of the counter-flushing groove also have certain influence on the sealing optimization effect, and the counter-flushing groove can be optimized in a certain range through simulation calculation according to different engine models and working environments. Under the condition of similar counter-punching groove area, the reasons of sealing effect, processing and manufacturing and the like are comprehensively considered, and the circular arc counter-punching groove is better selected.

Fig. 6 is a comparison graph of the sealing effect of the inclined grate tooth of the reference step and the axial displacement change under the same working condition, and it can be seen that if the opposite-punching grate tooth provided by the invention is adopted, the flow can be obviously reduced, and the sealing effect is improved.

In conclusion, the structure of the reference step labyrinth is improved, so that the safety and the sealing effect are improved, the leakage amount is reduced, and the structure is simple and easy to realize.

Claims

1. A labyrinth sealing device based on the hedging principle comprises a labyrinth plate, step grates axially designed on the labyrinth plate, and step bushings matched with the step grates; the method is characterized in that: each step is provided with a step side wall and a step tail end face, and the step tail end face is provided with an inward-concave arc opposite punching groove; an arc impact surface is designed between the step side wall of each step and the step end surface; making two opposite side edges of the step tail end surface be a tail end surface A edge and a tail end surface B edge respectively; the side A of the current ith step is connected with the side B of the end face of the i-1 th step; the side B edge of the current i-th step is connected with the side A edge of the tail end surface of the i-th step through an arc opposite impact surface;

the central angle of the circular arc opposite impact surface is designed to be 180-240 degrees; two opposite side edges of the arc hedging surface are respectively connected with the side wall of the step and the edge of the tail end surface of the step; the side wall of the step is tangent to the arc hedging surface; one end of the side wall of the step, which is connected with the arc hedging surface, inclines outwards, so that the side surface of the step and the axial direction of the grate disc form an included angle of 6-10 degrees; in the adjacent two steps, an included angle between the step side wall of the ith step and the step tail end face of the (i-1) th step is designed to be 70-105 degrees; the step tail end surface of each step is lower than the side B, and 2Ra & gt a is satisfied between the radius Ra of the circular arc hedging surface and the radial width a of the step tail end surface;

when the air current is passing through comb tooth top department, nearly ladder bush one side can be because the resistance is less relatively and flow through the comb tooth top with higher speed to in the impact slot is gone to the circular arc along ladder bush wall efflux, form clockwise vortex under the influence to the impact slot, go out with higher speed reverse rush at circular arc impact slot mouth department, with former tooth jet formation offset.

2. The labyrinth sealing device based on the hedging principle as claimed in claim 1, wherein: the concave arc opposite-flushing groove can also be an inverted trapezoidal groove or a trapezoidal groove.