A stepped labyrinth seal structure with a flow dividing channel

Abstract

The application provides a stepped labyrinth sealing structure with a shunt passage. The shunt passage is arranged between the two steps of the sealing bush, so that part of the airflow is backflowed into the shunt passage before the tooth top of the second step, thereby inhibiting the leakage of the airflow. The inlet of the shunt passage is arranged between the first step and the second step of the bush, and the outlet is arranged on the second step. After the airflow flows through the first step of the labyrinth, the airflow is divided into two parts, one part of the airflow flows to the second step along the original labyrinth passage, and the other part flows into the shunt passage. The airflow in the shunt passage is subjected to the frictional resistance of the wall surface, so that the pressure is reduced. The pressure at the outlet of the shunt passage is lower than the pressure in the tooth cavity between the first step and the second step of the labyrinth, so that the airflow is backflowed into the shunt passage before the gap between the tooth tops of the second step of the labyrinth, and the leakage flow of the airflow is reduced. The method can improve the sealing performance of the labyrinth without affecting other system functions, without changing the structural parameters such as the size and position of the labyrinth sealing, and the method is simple and feasible.

Description

Technical Field

[0001] This application belongs to the field of aero-engine technology, and specifically relates to a comb-tooth sealing structure with a flow diversion channel. Background Technology

[0002] Grate-type sealing structures are a widely used sealing measure in aero-engines, primarily applied to bearing cavities, compressor stage interstages, turbine stage interstages, gas isolation, and cooling flow paths. For example, in the turbine stages, the pressure and temperature of the gas gradually decrease axially from left to right. There is a pressure difference between each stage rotor blade or stator blade, and gaps are unavoidable between turbine rotor and stator components. Consequently, high-pressure gas inevitably leaks into low-pressure areas without contributing to power. Therefore, from the perspective of improving engine performance, it is necessary to install sealing devices in these locations.

[0003] The function of the toothed sealing structure is mainly reflected in two aspects: First, it suppresses gas leakage to meet sealing requirements with minimal leakage. For example, turbine interstage sealing aims to minimize flow rate to reduce leakage losses. Excessive leakage of high-temperature, high-pressure gas into the bearing cavity will cause the bearing cavity temperature and pressure to rise, damaging the bearing and lubricating oil, and causing engine performance loss. Second, it controls the overall pressure balance of the engine and regulates the pressure distribution of the air system. For example, the overall engine pressure balance requires the reasonable distribution of pressure in each disc cavity of the air system to meet the bearing load-bearing capacity requirements and prevent stress concentration from damaging components.

[0004] Traditional sealing structures rely entirely on structural parameters, including tooth profile, number of teeth, and clearance, with the tooth clearance having a particularly significant impact on sealing characteristics. Under the condition that the tooth sealing structure remains unchanged, further reducing tooth leakage flow in aero-engine design can only be achieved by reducing the tooth clearance. However, in aero-engines, the tooth clearance cannot be reduced indefinitely due to the deformation of the rotor and stator, thus limiting the sealing effect. Therefore, how to further reduce gas leakage without changing the tooth clearance is a problem that needs to be solved in the design of air system sealing and cooling flow paths. Summary of the Invention

[0005] Objective of the Invention: Based on the above problems, this invention provides a stepped grate sealing structure with a flow-diverting channel. The aim is to improve the sealing effect with a larger gap, achieving the sealing level of a smaller gap. Simultaneously, it can improve sealing performance with the same gap, thereby further enhancing engine performance.

[0006] Technical solution: A stepped grate sealing structure with diversion channels includes a rotor and an annular bushing surrounding the rotor; the outer surface of the rotor forms several outer steps from front to back, and the diameter of the previous outer step is larger than the diameter of the next outer step, and a grate extending towards the bushing is formed between adjacent outer steps; a gap is formed between the grate and the bushing; the inner wall of the bushing is provided with several annular inner steps that correspond to the several outer steps, and the front end of one inner step is located between two adjacent grates; several diversion channels are provided on the inner steps, each diversion channel including an air inlet located on the front end face of the step and an air outlet located on the side of the step facing the rotor axial direction, and the air inlet and the air outlet are connected by the inner channels.

[0007] Furthermore, the diversion channels are evenly and discretely distributed along the circumference of the steps, and the circumferential spacing S of the channels is 3-6 times the equivalent diameter d of the channel opening section.

[0008] Furthermore, the outlet of the diversion channel needs to be located in front of the tooth tip gap of a comb, and the axial distance L between the outlet of the diversion channel and the tooth tip is 0.2-1 times the tooth tip gap c.

[0009] Furthermore, the diversion channel gradually expands from the air inlet to the air outlet, with the area gradually increasing, and the area of ​​the air outlet is 1.2-3 times the area of ​​the air inlet.

[0010] Furthermore, the air inlet of the diversion channel is located between the two steps of the bushing, and the step height H is 1.5-3 times the opening section height h.

[0011] Furthermore, the diversion channel is only opened between the first and second stage grates, or a diversion channel structure is added between subsequent grates.

[0012] Furthermore, the diversion channel structure is set on the stator bushing of the stepped tooth grate sealing structure.

[0013] Beneficial effects: Compared with existing technologies, the stepped grate sealing structure with a diversion channel provided by this invention adds an air passage to the original grate sealing air path, thus forming an airflow barrier. When the grate gap changes significantly, it creates a strong blocking effect on the original sealing air path, mitigating the increased leakage caused by the increased gap to a certain extent, increasing energy dissipation inside the tooth cavity, and thus reducing fluid leakage in the original air path. Simultaneously, regardless of whether the grate gap is designed to be large or increased due to wear, the diversion channel always functions. Attached Figure Description

[0014] Figure 1 This is a schematic cross-sectional view of the stepped comb sealing structure with a diversion channel in this invention.

[0015] Figure 2 for Figure 1Enlarged view of a portion of position A in the middle.

[0016] Figure 3 This is a schematic diagram of the circumferential distribution of the diversion channels on the steps inside the bushing.

[0017] Figure 4 This is a three-dimensional schematic diagram of a diversion channel.

[0018] Figure 5 This is a schematic diagram of the cross-section of the diversion channel opening.

[0019] Figure 6 (a) is a schematic diagram of the streamline of the stepped comb seal structure with diversion channel in this application, calculated by numerical simulation.

[0020] Figure 6 (b) is a schematic diagram of the flow line of numerical simulation calculation of the existing toothed sealing structure. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings.

[0022] Typically, controlling the gap in a toothed sealing structure is challenging. This is because vibration, deformation, and wear make it difficult to maintain a small gap, resulting in a gap between the teeth and the bushing that is not too small. A larger gap leads to increased leakage. To overcome these problems, this application proposes a toothed sealing structure that effectively reduces gas leakage in the sealed flow path without excessively pursuing a small sealing gap.

[0023] Please combine Figures 1 to 4 As shown, the stepped grate sealing structure with diversion channels provided by the present invention includes a rotor 3 and an annular bushing 2 surrounding the rotor 3. The outer surface of the rotor 3 forms several outer steps 5 from front to back, with the diameter of the preceding outer step 5 being larger than the diameter of the following outer step 5. Grate teeth 6 extending towards the bushing are formed between adjacent outer steps. A gap is formed between the grate teeth 6 and the bushing. The inner wall of the bushing 2 is provided with several annular inner steps 7 corresponding to the several outer steps, and the front end of one inner step 7 is located between two adjacent grate teeth 6. Several diversion channels 1 are provided on the inner steps 7. Each diversion channel 1 includes an air inlet 8 located on the front end face of the step and an air outlet 9 located on the side of the step facing the rotor axial direction 4. The air inlet 8 and the air outlet 9 are connected by an inner channel.

[0024] Please combine Figure 2As shown, by setting a diversion channel 1 on the inner step 7, the airflow is divided into two streams after passing through the first-stage grate S1. One stream flows along the original grate channel to the second-stage grate S2, and the other stream flows into the diversion channel 1. The airflow experiences frictional resistance from the wall in the diversion channel 1, causing a pressure reduction. The pressure at the channel outlet is lower than the pressure in the inter-grate cavity between the first and second-stage grates. Therefore, the airflow flows back into the diversion channel 1 before the tooth tip gap of the second-stage grate S2, reducing the leakage flow. The air inlet 8 of the diversion channel 1 is located between the two steps of the bushing, and the step height H is 1.5-3 times the opening section height h.

[0025] like Figure 2 and Figure 3 As shown, in this embodiment, the diversion channels 1 are uniformly and discretely distributed along the circumference of the steps, and the circumferential spacing S of the channels is 3-6 times the equivalent diameter d of the channel opening section. The outlet of the diversion channel 1 needs to be located in front of the tooth tip gap of a comb, and the axial distance L between the outlet 9 of the diversion channel 1 and the tooth tip is 0.2-1 times the tooth tip gap c. The diversion channel 1 forms a gradually expanding inner channel from the inlet 8 to the outlet 9, with the area gradually increasing. The area of ​​the outlet 9 is 1.2-3 times the area of ​​the inlet 8. Figure 2 and Figure 3 In the diagram, c represents the tooth tip clearance; L represents the axial distance between the channel outlet surface and the tooth tip; H represents the step height; h represents the channel inlet section height; S represents the channel circumferential spacing distance; and d represents the equivalent diameter of the channel opening section.

[0026] Under a fixed inlet and outlet pressure ratio of the grate teeth, by changing the geometric parameters, numerical simulation was performed using the finite volume numerical simulation software Ansys Fluent to conduct quantitative leakage flow analysis, and the streamline calculation results of the grate sealing structure with flow diversion channel in this application were obtained. Figure 6 As shown in (a), compared to Figure 6 (b) shows the streamline calculation results of the existing grating sealing structure without a flow diversion channel. A comparison can be made to see that... Figure 6 (a) The airflow into the diversion channel before the tooth tip of the central grate suppresses the flow leakage of the original sealing air path at the tooth tip gap, thus improving the sealing effect of the grate. Under the condition of maintaining a gap of 0.3 mm, the leakage of the grate with the diversion channel can be reduced by 10% compared with the prior art.

[0027] In summary, the grate sealing structure provided in this application adds an air passage to the original grate sealing air path, thus forming an airflow barrier. When the grate gap changes significantly, it creates a strong blocking effect on the original sealing air path, mitigating the increased leakage caused by the increased gap to a certain extent, increasing energy dissipation inside the tooth cavity, and thus reducing fluid leakage in the original air path. Simultaneously, regardless of whether the grate gap is designed to be large or increased due to wear, the flow diversion channel always functions. Compared with the air vents in the existing grate sealing active control method, the grate sealing structure of this application, while reducing flow leakage, effectively reduces the processing technology, avoids the design challenge of external air venting, and improves the applicability of the structure by creating internal openings on the basic stepped teeth.

[0028] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A stepped grate sealing structure with a diversion channel, characterized in that, Includes a rotor and an annular bushing surrounding the rotor; the outer surface of the rotor forms several outer steps from front to back, and the diameter of the previous outer step is larger than the diameter of the next outer step, and a grating tooth extending towards the bushing is formed between two adjacent outer steps; a gap is formed between the grating tooth and the bushing. The inner wall of the bushing is provided with several annular inner steps that correspond to and cooperate with the several outer steps, and the front end of one inner step is located between two adjacent teeth; the inner step is provided with several diversion channels, each diversion channel including an air inlet located on the front end face of the step and an air outlet located on the face of the step facing the rotor axial direction, and the air inlet and the air outlet are connected by an inner channel.

2. The stepped grate sealing structure with diversion channel according to claim 1, characterized in that, The diversion channels are evenly and discretely distributed along the circumference of the steps, and the circumferential spacing S of the channels is 3-6 times the equivalent diameter d of the channel opening section.

3. The stepped grate sealing structure with a diversion channel according to claim 1 or 2, characterized in that, The air outlet of the diversion channel is located in front of the tooth tip gap of a comb, and the axial distance L between the air outlet of the diversion channel and the tooth tip is 0.2-1 times the tooth tip gap c.

4. The stepped grate sealing structure with diversion channel according to claim 3, characterized in that, The diversion channel gradually expands from the air inlet to the air outlet, with the area gradually increasing. The area of ​​the air outlet is 1.2-3 times that of the air inlet.

5. The stepped grate sealing structure with diversion channel according to claim 4, characterized in that, The air inlet of the split channel is located between two steps of the bushing, and the step height H is 1.5-3 times the opening section height h.

6. The stepped grate sealing structure with diversion channel according to claim 5, characterized in that, The diversion channel is only opened between the first and second stage grates, or a diversion channel structure is added between subsequent grates.

7. The stepped grate sealing structure with diversion channel according to claim 1, characterized in that, The diversion channel structure is set on the stator bushing of the stepped tooth grate sealing structure.

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