CN113685234B - Labyrinth sealing device based on hedging principle - Google Patents

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

A Grate Sealing Device Based on Hedging Principle

technical field

The invention relates to the field of aero-engine sealing, in particular to a grate sealing device based on the hedging principle.

Background technique

Grate seal is an effective non-contact sealing structure widely used in aero-engines. The grate seal has the advantages of simple structure, long service life, easy maintenance, and high reliability at high temperature and high speed. The sealing quality of the edge gas seal, the internal flow air seal and the oil seal in the main bearing oil seal system, to a large extent, controls the distribution of the air flow in the entire engine cooling network, which directly affects the efficiency of the engine. and reliability. If the leakage flow rate of the grate seal is larger than the design value, it will directly reduce the efficiency and performance of the engine. If the leakage flow rate of the grate seal is too small, it will cause the airflow to heat up significantly and the thermal expansion of the rotor to increase, shortening the service life of the engine. Therefore, the grate design that can improve the sealing effect is of great significance for improving the performance of aero-engines.

The traditional stepped grate is a non-contact dynamic sealing structure, as shown in Figure 1, which consists of a grate disc 1 (rotor) and a stepped bushing 2 (stator). There are more than two grate teeth 3 on the grate tooth plate 1 in the axial direction, and there is a height difference between the heights of the grate teeth 3 along the axial direction of the grate tooth plate 1, which is distributed in steps; The tooth cavity 4 is formed. The stepped bushing 2 is a sealing bushing sleeved on the outside of the grate plate 1, and its side wall is stepped in the axial direction, which matches the height difference of each grate tooth 3 in the axial direction of the grate plate 2. The circumferential side wall of each step is Corresponding to the tooth crest of one grate tooth 3, a gap is left between the tooth crest of each grate tooth 3 and its corresponding step side wall. When the airflow passes through the gap between the two, it is accelerated by the throttling to generate a jet area, part of the pressure energy is converted into kinetic energy, and the airflow collides with the inner wall of the stepped bushing 2 to generate a recirculation area. The lower part of the tooth cavity 4 creates a larger recirculation zone. Due to the existence of these recirculation zones, the airflow energy is converted into heat energy and consumed under the action of turbulent flow and viscous dissipation, and finally the sealing effect is achieved.

For stepped grate teeth, the sealing effect mainly relies on the throttling effect at the tooth top and the eddy current dissipation between the tooth cavities. When the jet impinges on the bushing part, it will form stagnation, and eddy current will be formed due to shearing action. When the positive axial displacement is large, it will also form throttling with the bushing, further reducing the flow coefficient.

SUMMARY OF THE INVENTION

Aiming at the current situation that the existing step grate sealing effect of aero-engine is limited, the sealing effect is easy to lose, and the safety is low, the present invention proposes a grate sealing structure based on the hedging principle that can improve the sealing effect.

The grate sealing device based on the hedging principle of the present invention comprises a grate disc, a stepped grate designed axially on the grate disc, and a stepped bush matched with the stepped grate.

Wherein, in the step bushing, each step has a step side wall and a step end surface, and a concave arc hedging groove is designed on the step end surface. Therefore, when the airflow passes through the tooth top of the grate, the side near the stepped bushing will flow through the tooth top of the grate at a high speed due to the relatively small resistance, and the jet will flow along the wall of the stepped bushing to the arc hedging. In the groove, a clockwise eddy current is formed under the influence of the hedging groove, and it rushes out at a higher speed at the notch of the arc hedging groove, forming a hedging with the original interdental jet.

The advantages of the present invention are:

1. The grate sealing device of the present invention is based on the hedging principle, and a concave annular hedging groove is added at each step of the step bushing, so that the air jet flows into the hedging groove along the wall surface, and forms a clockwise direction under the influence of the hedging groove. The eddy current rushes out at a relatively high speed at the notch, and forms a hedge with the jet between the original teeth, reducing the ventilation effect of the grate teeth and achieving the purpose of sealing optimization;

2. The grate tooth sealing device of the present invention is based on the hedging principle, and the appropriate size of the hedging groove space enables the full development of the dissipative vortex behind the tooth, which further intensifies the dissipation of energy;

3. The grate sealing device of the present invention is based on the hedging principle. Through the design of the hedging groove, the contact between the airflow and the wall surface is increased, and the viscous shear dissipation is also increased to a certain extent; Hedging the formation of eddy currents, the energy dissipation is greater, and the sealing effect is more obvious.

4. The grate sealing device based on the hedging principle of the present invention has lower sensitivity to the gap change and stronger stability when the grate gap changes.

Description of drawings

Figure 1 is a schematic diagram of the structure and flow field of a traditional stepped inclined grate.

2 is a schematic diagram of the structure and flow field of the grate sealing device based on the hedging principle of the present invention.

3 is a partial enlarged schematic diagram of each step in the grate sealing device based on the hedging principle of the present invention.

4 is a schematic diagram of the trapezoidal hedging groove structure of the grate sealing device based on the hedging principle of the present invention;

5 is a schematic diagram of the structure of the inverted trapezoidal hedging groove of the grate sealing device based on the hedging principle of the present invention;

6 is a comparison diagram of the sealing effect of the grate tooth sealing device of the present invention and the traditional stepped inclined grate tooth structure under the same conditions obtained by simulation.

In the picture:

1-grate tooth plate 2-step bushing 3-grate tooth

4-Tooth cavity 5-Step side 6-Arc hedging surface

7-Step end face

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings.

The invention is based on the grate sealing device based on the hedging principle. For the transmission step grate, the stepped bushing 2 is improved, and each step in the stepped bushing 2 is designed to have a stepped side surface 5, a hedging surface 6 and a step end surface 7. As shown in Figure 2 and Figure 3.

Among them, the step side 5 is the surface opposite to the tooth top of the grate tooth 3; the step end surface 7 is the surface facing the end of the grate tooth plate 2; let the two opposite sides of the step side 5 be the side A side and the side B side; the step end surface 7 The two opposite sides are the end face A side and the end face B side respectively. Then the side A of the current i-th step is connected with the end face B of the i-1 step; the side B of the current i-th step and the end face A of the i-th step are hedged by an arc. Face 6 is connected; let the straight sides on the opposite sides of the arc facing face 6 be straight side A and straight side B, respectively, then there is straight side A and the end face A side, and the straight side B is connected with the side B side, so that A concave arc hedging groove is formed on the outer side of the end face of the step.

In the grate sealing device of the above structure, the grate plate 1 includes at least two grate teeth 3, each of which has the same shape, and the spacing between adjacent grate teeth 3 is equal; It is equal to the radial distance between the tooth tops of the corresponding grate teeth 3 .

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

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

b. The end of the stepped side surface 5 and the arc counterface 6 is inclined outward, so that the stepped side surface 5 and the grate tooth plate 2 form an included angle of 6 to 10 degrees in the axial direction.

c. The central angle γ of the arc hedging surface 6 is designed to be 180°～240°;

d. The angle α between the step side surface 5 of the i-th step and the step end face 7 of the i-1-th step is designed to be 70° to 105°.

In order to achieve a better sealing effect, the position of the end surface of the step in each step is designed to be lower than the side B side, that is, closer to the grate 3 corresponding to the step, and the radius Ra of the arc facing surface 6 and the radial direction of the end surface of the step are designed. The width a must satisfy 2Ra>a.

The invention is based on the grate sealing device based on the hedging principle, and a concave arc hedging groove is added at each step. When the airflow passes through the tooth crest of the grate tooth 3, the side near the stepped bushing 2 will flow through the tooth crest of the grate tooth 3 at a high speed due to the relatively small resistance, and will jet along the wall of the stepped bushing 2 to the arc hedging. In the groove, a clockwise eddy current is formed under the influence of the hedging groove, and it rushes out at a high speed at the notch of the arc hedging groove, forming a hedge with the original inter-tooth jet, reducing the ventilation effect of the grate teeth, and achieving the optimal sealing effect. At the same time, the proper size of the space of the hedging groove enables the full development of the dissipative vortex after the tooth, which further intensifies the dissipation of energy; in addition, the present invention increases the contact between the airflow and the wall surface, and also increases the viscous shear dissipation to a certain extent. .

In the present invention, the shape of the concave annular hedging groove at each step based on the hedging principle can be designed as a trapezoidal groove, an inverted trapezoidal groove, etc., as shown in FIG. 4 and FIG. 5. Among them, the geometric parameters such as the depth, angle, and shape of the hedging groove will also have a certain impact on the sealing optimization effect. According to different engine models and working environments, the optimization can be carried out within a certain range through simulation calculations. However, under the condition that the area of the hedging groove is similar, and considering the reasons of sealing effect and processing and manufacturing, it is better to select the aforementioned arc hedging groove.

Figure 6 shows the comparison chart of the sealing effect of this scheme and the reference step inclined grate when the axial displacement changes under the same working conditions. Improve sealing effect.

To sum up, the present invention improves the safety and sealing effect by improving the structure of the reference step grate, reduces the leakage, and has a simple structure and is easy to implement.

Claims (2)

1. A grate sealing device based on the hedging principle, comprising a grate disc, a stepped grate designed axially on the grate disc, and a stepped bush matched with the stepped grate; it is characterized in that: each step has The side wall of the step and the end face of the step, and the end face of the step is designed with a concave arc hedging groove; the side wall of each step and the end face of the step are designed with an arc hedging surface; let the two opposite sides of the end face of the step be respectively The A side of the end face and the B side of the end face; then the side A side of the current i-th step is connected to the end face B of the i-1th step; the side B of the current i-th step is connected to the i-th step. The end face A of the end face is connected by the arc hedging face; The central angle of the arc facing surface is designed to be 180° to 240°; the opposite sides of the arc facing surface are respectively connected to the edge of the side wall of the step and the edge of the end face of the step; the side wall of the step is tangent to the arc facing surface; The connecting end of the arc facing surface is inclined outward, so that the side of the step and the axial direction of the grate tooth plate form an included angle of 6 to 10 degrees; in the two adjacent steps, the side wall of the i-th step and the i-1th step are at an angle of 6 to 10 degrees; The included angle between the end faces of the step is designed to be 70°～105°; the position of the step end face of each step is lower than the side B side, and the radius Ra of the arc facing surface and the radial width a of the step end face satisfy 2Ra>a; When the airflow passes through the tooth top of the grate, the side near the stepped bushing will flow through the tooth top of the grate at a high speed due to the relatively small resistance, and jet along the wall of the stepped bushing to the arc hedging groove. A clockwise eddy current is formed under the influence of the counter-flushing groove, which rushes out at a high speed in the reverse direction at the notch of the circular counter-flushing groove, forming a hedge with the original interdental jet. 2 . The grate sealing device based on the hedging principle according to claim 1 , wherein the concave arc hedging groove can also be an inverted trapezoidal groove or a trapezoidal groove. 3 .

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