A negative feedback grate sealing device based on wind resistance and thermal deformation

Abstract

The present invention discloses a negative feedback grate sealing device based on wind resistance thermal deformation, which belongs to the technical field of non-contact rotor-stator sealing of aircraft engines. This sealing device mainly includes a thermal expansion grate disc, an inverted grate portion at the disc end, and a corresponding stator sealing bushing that can bend the flow, forming flow gaps, curved cavity sections, tooth top gaps, grate tooth cavities and other flow parts between the rotor and the stator. Starting from the perspective of the grate utilizing wind resistance configuration, the present invention adds a flow turning curved cavity section, an inverted grate segment and a stator bushing part that cooperates therewith, so that the grate and the stator bushing under the influence of wind resistance have the same direction of deformation deviation, thereby achieving a relatively stable gap between the grate and the bushing, forming a negative feedback mechanism to control the flow, and forming a wind resistance negative feedback grate configuration that is insensitive to deviation under high load working environment, to a certain extent solving the problem of grate rubbing and failure caused by deviation under the influence of wind resistance, reducing the requirements for grate process accuracy, and improving engine efficiency and safety.

Description

Technical Field

[0001] The present invention relates to the field of sealing of aviation engine air systems, and in particular to a grate sealing device which can utilize windage heat to control grate deformation at high temperature and high speed, thereby realizing negative feedback function of gap and flow change. Background Art

[0002] The aircraft engine air system is the collective term for the air flow paths connecting the rotor and stator, or between the rotor and stator, inside and outside the engine's main flow path. It comprises a network of various flow paths connected in series and parallel, each with its own function. The air system performs crucial tasks, including cooling components such as the turbine rotor and stator, sealing bearing cavities, controlling axial loads, preventing turbine gas intrusion, and providing anti-icing air. As engine performance requirements continue to rise, engine speeds and turbine inlet temperatures are also increasing, making air system sealing issues increasingly pressing. The design of sealing devices directly impacts overall engine performance. Comparisons have shown that advanced sealing technologies can effectively reduce fuel consumption and leakage flow, thereby improving engine efficiency and lowering costs. Comb elements, the most widely used non-contact sealing structure, offer advantages such as simple structure, ease of fabrication, high reliability, and low cost. Modifying the configuration of the comb element can effectively alter its heat transfer and flow characteristics, thereby meeting different functional requirements and achieving efficient sealing under specific circumstances.

[0003] The traditional stepped bevel grate is a common non-contact dynamic sealing structure, and its radial cross section is as follows: Figure 1 As shown, the rotor grate disc rotates at high speed with the shaft, and the stator part is connected and fixed to the outer casing by bolts and other structures. The upper edge of the grate disc generally has more than 3 grate structures (5 in the figure), and the geometry is similar. There is an arc-shaped tooth cavity between adjacent grate teeth, and there is a certain height difference, which is equal to the height difference between the stator steps corresponding to adjacent grate teeth. Traditional grate sealing mainly relies on three parts: a very small radial gap is left between the top of the grate teeth and the step to control the airflow and achieve throttling sealing; tooth cavity vortex is formed between adjacent grate teeth to dissipate the eddy current of flow energy, as well as near-wall flow and turbulent energy dissipation; after the fluid passes through the tooth top gap, the jet generated by throttling acceleration hits the inner wall of the stator step, which will cause energy loss and form a recirculation zone.

[0004] In actual engineering applications, under high-temperature and high-speed operating conditions, the rotor undergoes centrifugal and thermal forces, causing a certain amount of radial deformation. This results in a reduction in grate clearance, and the airflow through the grate element generates a certain amount of windage resistance and temperature rise. Due to the high-speed rotation of the grate disc components and repeated friction with the airflow, the grate disc temperature rises further, further increasing the rotor deformation, exacerbating the positive feedback process of reduced grate clearance, reduced leakage flow, and increased temperature rise. Therefore, a large clearance margin is required during cold assembly to accommodate the grate deformation during operation. However, due to process variations and transient processes, the actual radial clearance of the grate element will vary. Under these operating conditions, this relative deviation is further amplified, increasing the uncertainty of the hot clearance. Under the influence of multi-physics coupling and the system's positive feedback mechanism, more serious consequences such as rotor-to-stationary friction can occur. However, increasing the initial radial clearance will increase leakage flow, weaken the sealing effect, and reduce engine efficiency. Summary of the Invention

[0005] In response to the above problems, the present invention proposes a negative feedback grate sealing device based on windage thermal deformation. By changing the traditional grate configuration to utilize windage heat, the device can achieve stable control of the sealing gap under high-speed and high-windage environment, reduce the impact of gap changes caused by high load, deviation and transition state, and significantly improve engine efficiency and safety.

[0006] The invention discloses a negative feedback grate sealing device based on wind resistance thermal deformation, comprising a thermal expansion grate disc, an inverted grate portion at the disc end and a corresponding stator sealing bushing capable of deflecting flow.

[0007] The thermal expansion grate disc has an inverted grate section circumferentially located inside the annular cavity designed on the stator's sealing sleeve. A rotor-to-stationary gap is formed between the outer wall of the annular cavity and the outer side of the grate disc. A curved cavity section is formed between the end of the grate disc and the bottom surface of the stator's annular cavity. A tooth tip gap is formed between the inverted grate tooth tips and the inner circumferential wall of the annular cavity.

[0008] The airflow flows through the inlet, through the rotor-stator gap, hits the bottom surface of the annular cavity in the stator, and then flows radially along the curved cavity section. Then it flows in the opposite direction along the axial direction, and flows through the tooth top gaps and tooth cavities of each level of inverted grate teeth in the lower half in turn. Finally, after passing through the tooth top of the last level of grate teeth, it flows out of the grate teeth and merges into the rear cavity. The sealing effect is achieved through the throttling effect of the tooth top and the dissipation along the way. Afterwards, the airflow in the rear cavity rubs against the rotating parts to generate wind resistance.

[0009] When the grate gap decreases, the leakage flow decreases, the windage temperature rise increases, and the grate disc temperature increases. At this time, the grate gap will increase due to the increase in the rotor-stator deformation, which will increase the grate flow, thereby reducing the windage temperature rise, forming a negative feedback, and suppressing the impact of the original deviation; when the grate gap increases, the leakage flow increases, the windage temperature rise decreases, and the grate disc temperature decreases. At this time, the grate gap will decrease due to the reduction in the rotor-stator deformation, reducing the leakage flow, improving the sealing level, increasing the windage temperature rise, forming a negative feedback, and realizing the flow change amplitude control under high wind resistance conditions, keeping the grate sealing ability under the influence of deviation in a relatively stable state.

[0010] The advantages of the present invention are:

[0011] 1. The grate sealing device based on wind resistance, thermal deformation and negative feedback of the present invention makes the grate gap and leakage flow more stable when there is a deviation compared with traditional grate teeth;

[0012] 2. The grate sealing device based on wind resistance thermal deformation negative feedback of the present invention can, to a certain extent, solve the problem of grate deformation caused by the wind resistance of the high-speed rotating bolts in the chamber near the grate disc, which increases the friction.

[0013] 3. The grate sealing device based on windage thermal deformation negative feedback of the present invention can reduce the sensitivity of the grate gap to process deviation and transition state deviation, and reasonably reduce the precision requirements of processing deviation;

[0014] 4. The present invention is based on a wind resistance thermal deformation negative feedback grate tooth sealing device, which has a simple tooth shape, is easy to process and has low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Schematic diagram of the traditional step grate structure.

[0016] Figure 2 This is a structural schematic diagram of the grate sealing device based on wind resistance thermal deformation negative feedback of the present invention.

[0017] Figure 3 This is a working principle diagram of the grate sealing device based on wind resistance thermal deformation negative feedback of the present invention.

[0018] Figure 4 This is a working process diagram of the grate sealing device based on wind resistance thermal deformation negative feedback of the present invention. DETAILED DESCRIPTION

[0019] The present invention will be further described in detail below with reference to the accompanying drawings and specific implementation examples.

[0020] The present invention is based on a windage heat deformation negative feedback grate sealing device, which utilizes the windage heat generated by itself and adjacent chambers through non-contact static-rotor sealing technology to achieve negative feedback control of flow and deformation and reduce the impact of deviation.

[0021] The present invention is based on the structural improvement of traditional comb teeth, such as Figure 2 As shown, the designed rotor is a thermal expansion grate disc with inverted grate teeth at the disc end, which has a component that creates high wind resistance. For example, the thermal expansion grate disc in the present invention has circumferentially distributed high-radius rotating bolts for fixed connection. The thermal expansion grate disc has an annular surface in the circumferential direction, and two or more straight-through inverted grate teeth with a forward inclination angle α of 0 to 90 degrees are designed on the outer wall at the end of the annular surface along the axial direction of the thermal expansion grate disc; there are arc-shaped or trapezoidal tooth cavities between adjacent inverted grate teeth, and all inverted grate teeth are at the same rotation radius height. The above-mentioned thermal expansion grate disc is connected to the rotating shaft and other parts according to the specific structure.

[0022] The outer wall of the stator sealing sleeve is designed to surround the periphery of the rotor inverted grate teeth, and the outer wall of the stator sealing sleeve extends axially to slightly beyond the end of the annular surface of the rotor, after which it turns radially, and further extends to slightly beyond the top of the inverted grate teeth, and then turns axially to form an inner wall of the stator sealing sleeve with a certain thickness. The inner wall of the stator sealing sleeve cooperates with the inverted grate teeth to form a seal; and the inner wall of the stator sealing sleeve extends all the way to the back of the last level of inverted grate teeth. Therefore, through the design of the above-mentioned stator sealing sleeve, each straight-through inverted grate tooth is located inside the annular cavity finally formed at the left end of the stator sealing sleeve. The right end of the stator sealing sleeve is connected to the casing and other parts according to the specific structure.

[0023] In the stator sealing device of the above structure, there is a certain gap between the outer wall of the annular surface of the rotor and the outer wall of the stator sealing sleeve in the circumferential direction, which is called the rotor-static gap; at the same time, there is a certain gap between the end of the annular surface of the rotor and the bottom surface of the annular cavity of the stator, which is called the curved cavity section; there is a certain gap between the tooth top of each straight-through inverted grate tooth and the inner side wall of the annular cavity in the circumferential direction, which is called the tooth top gap.

[0024] In the above structural sealing device, it is also designed:

[0025] a. The inner wall thickness of the annular cavity of the stator is 0.5mm to 5mm, preferably 1mm to 2mm.

[0026] b. The bottom surface of the annular cavity of the stator is a downward-sloping inclined surface on the outside, which is parallel to the front side of the grate teeth, and the arc transition design is adopted between the bottom surface of the annular cavity and the outer wall of the annular cavity.

[0027] c. The width a of the rotating-static gap should be greater than 0.2% of the rotation radius of the thermal expansion grate disc.

[0028] d. The width of the curved cavity section (the horizontal distance between the end of the annular surface of the rotor and the bottom surface of the stator annular cavity) c is between 1mm and 4.5mm. If the width of the curved cavity section is designed to be too small, an additional throttling effect will appear, generating wind resistance, reducing the axial deformation margin of the rotor, and prone to axial collision and wear; if the width of the curved cavity section is too large, it will cause the deformation of the stator bushing end to be too large, reduce the wind resistance thermal negative feedback effect, and may cause lower comb teeth to collide and wear.

[0029] e. The width of the annular cavity is the sum of the width of the rotating-static gap, the width of the tooth top gap, the height of the grate teeth and the thickness of the end of the grate tooth disc.

[0030] f. The width d of the tooth top gap is 1 / 1000 to 5 / 1000 of the rotation radius of the thermal expansion grate disc.

[0031] Through the above design, the grate tooth structure has a certain axial and radial margin while maintaining normal air entrainment sealing capability, reducing friction, rationally utilizing wind resistance and thermal expansion deformation, and realizing negative feedback function.

[0032] In summary, the present invention eliminates the forward grate structure in the rotor, and the rotor is completely sealed by the inverted grate teeth of the grate disc and the inner wall of the stator sealing sleeve. At the same time, the airflow at the inlet is guided in the direction by the corresponding gap design that can bend the flow. Figure 2 As shown, when the sealing device of the present invention is working, the left side is the air inlet. The air flows through the inlet and flows through the rotor-stator gap. After hitting the arc part of the bottom surface of the annular cavity in the stator, it flows radially along the curved cavity section, and then flows in the opposite direction along the axial direction. It flows through the tooth top gaps and tooth cavities of each level of the lower half in sequence, and finally flows out of the grate teeth after passing through the tooth top of the last level of grate teeth and merges into the rear cavity. The sealing effect is achieved through the throttling effect of the tooth top and the dissipation along the way; then the airflow in the rear cavity rubs against the rotating parts such as the disk or bolt to generate wind resistance, as shown in FIG. Figure 3 shown.

[0033] During the actual operation at high temperature and high speed, due to the influence of process and transition state deviations, the existence of windage heat will cause deformation deviations in the traditional stepped grate teeth, forming a positive feedback mechanism, which will cause the sealing gap to gradually deviate from the design point and become unstable, which is prone to the consequences of friction or excessive leakage flow, posing a threat to the efficiency and safety of the engine. Therefore, the present invention focuses on the system level, starting from the perspective of the grate teeth utilizing the windage configuration, through the design of the inverted grate teeth and the corresponding stator sealing bushing, so that the inverted grate teeth and the stator sealing bushing under the influence of windage will have the same direction of deformation deviation, so as to achieve a relatively stable gap between the inverted grate teeth and the stator sealing bushing, forming a negative feedback mechanism to control the flow, such as Figure 3 The present invention utilizes the coupling mechanism and law of leakage flow, grate temperature, and rotor and stator deformation to form a windage negative feedback grate configuration that is insensitive to deviation under high-load working conditions, thereby improving engine efficiency and safety.

[0034] Many studies have shown that the leakage flow of the grate sealing structure is positively correlated with the tooth top clearance. The negative feedback grate sealing device of the present invention will appropriately adjust the tooth top clearance through negative feedback grate deformation under high speed and high wind resistance working conditions, thereby having better flow stability; through the same-direction deformation deviation of the rotor and stator, the sensitivity of the grate clearance to the original deviation is effectively reduced; and within a certain range, the higher the wind resistance, the more obvious the optimization effect is compared with the traditional stepped grate. The working process of the present invention is as follows: Figure 4 As shown, it is first assumed that the process or transition state deviation changes the tooth top gap. When the deviation and transition state reduce the tooth top gap, the leakage flow decreases, the wind resistance temperature rise increases, and the grate disc temperature increases. At this time, the tooth top gap will increase due to the increase in the rotor and stator deformation, which will increase the grate flow, thereby reducing the wind resistance temperature rise, forming a negative feedback, and suppressing the impact of the original deviation; when the deviation and transition state increase the tooth top gap, the leakage flow increases, the wind resistance temperature rise decreases, and the grate disc temperature decreases. At this time, the grate gap will decrease due to the reduction in the rotor and stator deformation, reducing the leakage flow, improving the sealing level, increasing the wind resistance temperature rise, forming a negative feedback, and realizing the flow change amplitude control under high wind resistance conditions, and keeping the grate sealing ability under the influence of the deviation in a relatively stable state.

[0035] The present invention utilizes the deformation characteristics of the rotor and stator of the sealing grate teeth under the action of wind resistance and heat, and introduces a wind resistance and heat negative feedback mechanism to achieve stable control of the grate gap and sealing flow, reducing the sensitivity of the flow path to grate process and transition state deviations, thereby improving engine efficiency and safety.

Claims

1. A negative feedback grate sealing device based on wind resistance and thermal deformation, characterized by: The device comprises: a thermal expansion grate disc, an inverted grate portion at the disc end and a corresponding stator sealing bushing capable of deflecting flow; Among them, the inner circumference of the end of the thermal expansion grate disc is designed with an inverted grate tooth part; the inverted grate tooth part is located in the annular cavity designed on the stator sealing sleeve; a rotating-static gap is formed between the outer wall of the annular cavity and the outer side of the grate disc end; a curved cavity section is formed between the end of the grate disc and the bottom surface of the annular cavity of the stator; a tooth top gap is formed between the inverted grate tooth top and the circumference of the inner wall of the annular cavity; the air flow passes through the rotating-static gap through the inlet, impacts the bottom surface of the annular cavity in the stator, and then flows radially along the curved cavity section, and then flows in the opposite direction along the axial direction, and flows through the tooth top gaps and tooth cavities of each level of inverted grate teeth in the lower half in turn, and finally flows out of the grate teeth after passing through the tooth top of the last level and merges into the rear cavity, and the sealing effect is achieved through the throttling effect of the tooth top and the dissipation along the way; then the air flow in the rear cavity rubs against the rotating parts to generate wind resistance; When the sealing device is working, the airflow inlet is on the left side. The airflow flows through the rotor-stator gap through the inlet, hits the arc part of the bottom surface of the annular cavity in the stator, and then flows radially along the curved cavity section. Then it flows in the opposite direction along the axial direction, and flows through the tooth top gaps and tooth cavities of each level of inverted grate teeth in the lower half in sequence. Finally, after passing through the tooth top of the last level of grate teeth, it flows out of the grate teeth and merges into the rear cavity. The sealing effect is achieved through the throttling effect of the tooth top and the dissipation along the way. When the tooth top gap decreases, the leakage flow decreases, the windage temperature rise increases, and the temperature of the grate disc increases. At this time, the tooth top gap will increase due to the increase in the rotor and stator deformation, which will increase the grate flow, thereby reducing the windage temperature rise, forming a negative feedback, and suppressing the impact of the original deviation; when the tooth top gap increases, the leakage flow increases, the windage temperature rise decreases, and the temperature of the grate disc decreases. At this time, the tooth top gap will decrease due to the reduction in the rotor and stator deformation, reducing the leakage flow, improving the sealing level, increasing the windage temperature rise, and forming a negative feedback.

2. The negative feedback grate sealing device based on wind resistance and thermal deformation according to claim 1, characterized in that: There are more than two inverted grate teeth, and the forward inclination angle is 0~90°; there is an arc-shaped or trapezoidal tooth cavity between adjacent inverted grate teeth, and all inverted grate teeth are at the same rotation radius height.

3. The negative feedback grate sealing device based on wind resistance and thermal deformation according to claim 1, characterized in that: The inner wall thickness of the stator's annular cavity is 0.5mm~5mm.

4. The negative feedback grate sealing device based on wind resistance and thermal deformation according to claim 1, characterized in that: The bottom surface of the annular cavity of the stator is an inclined surface with an outer side inclined downward, and the inclined surface is parallel to the front side of the grate teeth facing it, and the bottom surface of the annular cavity and the outer wall of the annular cavity are designed with an arc transition.

5. The negative feedback grate sealing device based on wind resistance and thermal deformation as claimed in claim 1, characterized in that: The width a of the rotating-static gap should be greater than 0.2% of the rotation radius of the thermal expansion grate disc.

6. The negative feedback grate sealing device based on wind resistance and thermal deformation according to claim 1, characterized in that: The width of the curved cavity section is between 1 mm and 4.5 mm.

7. The negative feedback grate sealing device based on wind resistance and thermal deformation according to claim 1, characterized in that: The width of the annular cavity is the sum of the width of the rotating-static gap, the width of the tooth top gap, the height of the grate teeth and the thickness of the end of the grate tooth disc.

8. The negative feedback grate sealing device based on wind resistance and thermal deformation as claimed in claim 1, characterized in that: The width of the tooth top gap is 1 / 1000 to 5 / 1000 of the rotation radius of the thermal expansion grate disc.

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