Grate tooth sealing structure for enhancing sealing performance through inlet pre-rotation and interstage pre-rotation

Abstract

The invention provides a labyrinth sealing structure for enhancing sealing performance through inlet prerotation and interstage prerotation, and relates to the technical field of aero-engine and gas turbine sealing. A rotational flow device is additionally arranged in front of a labyrinth slit, so that flowing generates a tangential component, kinetic energy in the axial direction is decomposed into the combination of an axial component and the tangential component, the axial kinetic energy of airflow is reduced, the ventilation effect of the labyrinth slit is weakened, and then the sealing performance of labyrinth seal is enhanced. The height of the additional rotational flow device is slightly larger than the gap of the labyrinth slit, or the additional rotational flow device is given according to the machining level and does not invade a cavity formed by the labyrinth and the wall face as much as possible, and the total pressure loss induced by geometric sudden expansion is reserved to the maximum extent. The rotational flow ratio of air flow is reduced along with flowing, and in order to guarantee the on-way rotational flow ratio, rotational flow devices are also arranged between the labyrinth stages. For the rotating comb teeth, in order to achieve the maximum pre-swirling effect, the swirling device is arranged on the static wall face.

Description

Technical Field

[0001] The present invention relates to the technical field of sealing for aeroengines and gas turbines. Specifically, it relates to a labyrinth seal structure that enhances the sealing performance through inlet pre-whirl and inter-stage pre-whirl. Background Technique

[0002] Sealing technology is widely used in the secondary air system of aeroengines and gas turbines to control the flow distribution and pressure distribution in the air system. For aeroengines, lower sealing leakage can significantly improve the engine performance indicators. The AST (Advanced Subsonic Technology) research program implemented by NASA shows that the fuel consumption rate of future engines can be reduced by 10%, and the contribution of the progress of sealing technology is 2%-3%.

[0003] As one of the three major sealing technologies, the labyrinth seal belongs to a non-contact sealing device and is widely used for sealing between the stators of gas turbines, between the rotor and the stator, or between rotors with different speeds.

[0004] As Figure 1 shown, the labyrinth seal usually consists of several labyrinth teeth 3 and the wall surface 2 that cooperates with them. The labyrinth teeth 3 and the wall surface 2 form a labyrinth slot 4, and the labyrinth slot 4 is connected to the cavity 5. The inlet air flow pressure of the labyrinth seal is relatively high. When the air flow passes through the first labyrinth slot, the air flow accelerates and the pressure drops. Then the air flow enters the cavity 5. Due to the sudden expansion of the flow passage, the flow separates, forming separated flow and recirculation, as Figure 2 shown. Under the action of molecular viscosity and turbulent viscosity, the friction between fluid layers increases, and the mechanical energy of the air flow is converted into heat energy, resulting in a total pressure loss. The air flow alternately passes through the labyrinth slot and the cavity, and the above total pressure loss process is repeated continuously, and the total pressure of the air flow drops. The total pressure in the front cavity of the last-stage labyrinth teeth decreases, weakening the air-permeability effect of the last-stage labyrinth slot, thereby reducing the leakage flow rate of the labyrinth seal.

[0005] To facilitate the comparison of the sealing characteristics of different seals, the sealing characteristics are quantified by the leakage flow coefficient. Generally, the leakage flow coefficient is written as a functional relationship of the total pressure ratio between the inlet and the outlet:

[0006]

[0007] where q m is the flow rate through the seal, T t,in is the inlet total temperature, p t,in is the inlet total pressure, p t,out is the outlet total pressure, A is the characteristic area of the seal, K is a constant, and the value for air is The value for gas is In some experiments, the total static pressure ratio of the inlet and outlet is used to replace the total pressure ratio of the inlet and outlet, that is, the leakage flow coefficient is expressed as a function of the total static pressure ratio of the inlet and outlet. Summary of the Invention

[0008] In view of this, the purpose of the present invention is to provide a labyrinth seal structure that enhances the sealing performance through inlet pre-whirl and inter-stage pre-whirl.

[0009] The present invention adopts the following solutions:

[0010] The present application provides a labyrinth seal structure that enhances the sealing performance through inlet pre-whirl and inter-stage pre-whirl. A swirl device is provided in front of the labyrinth slot to generate a tangential component of the air flow, decomposing the axial kinetic energy into an axial component and a tangential component, thereby reducing the axial kinetic energy and enhancing the sealing characteristics.

[0011] Further, the height of the swirl device is slightly greater than the clearance of the labyrinth slot, or the minimum height given according to the processing level, so as to ensure that the swirl device does not overly intrude into the cavity formed by the labyrinth and the wall surface, thereby maximizing the total pressure loss induced by geometric sudden expansion.

[0012] Further, the swirl device is arranged upstream of the labyrinth slot or between two labyrinths, or any combination of the two.

[0013] Further, for a rotating labyrinth seal, the swirl device is arranged on the stationary wall surface and does not rotate with the rotor.

[0014] By adopting the above technical solutions, the present invention can achieve the following technical effects:

[0015] 1. A swirl device is provided in front of the labyrinth slot, which generates a tangential component of the air flow, thereby decomposing the kinetic energy along the axial direction into a combination of an axial component and a tangential component, reducing the axial kinetic energy of the air flow, weakening the air-permeable effect of the labyrinth slot, and enhancing the sealing performance of the labyrinth seal.

[0016] 2. The height of the swirl device is slightly greater than the clearance of the labyrinth slot and does not intrude into the cavity formed by the labyrinth and the wall surface as much as possible, so as to retain the total pressure loss induced by geometric sudden expansion to the greatest extent; the swirl ratio of the air flow will decrease as the flow progresses. Arranging the swirl device between the labyrinth stages can effectively ensure the swirl ratio.

[0017] 3. For a rotating labyrinth, arranging the swirl device on the stationary wall surface can achieve the maximum pre-whirl effect and enhance the sealing performance of the labyrinth seal. Description of the Drawings

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0019] Figure 1 is a schematic diagram of the working principle of labyrinth seal;

[0020] Figure 2 is a schematic diagram of the velocity field inside the labyrinth seal;

[0021] Figure 3 is a sectional view of a labyrinth seal structure for enhancing sealing performance through inlet pre-rotation and inter-stage pre-rotation according to an embodiment of the present invention Figure 1 ;

[0022] Figure 4 is a sectional view of a labyrinth seal structure for enhancing sealing performance through inlet pre-rotation and inter-stage pre-rotation according to an embodiment of the present invention Figure 2 ;

[0023] Figure 5 is a schematic diagram of some swirl devices of a labyrinth seal structure for enhancing sealing performance through inlet pre-rotation and inter-stage pre-rotation according to an embodiment of the present invention;

[0024] Figure 6 is a schematic diagram of the principle of the influence of inlet pre-rotation on the leakage characteristics of the labyrinth seal;

[0025] Figure 7 is some examples of the combined pre-rotation of a labyrinth seal structure for enhancing sealing performance through inlet pre-rotation and inter-stage pre-rotation according to an embodiment of the present invention.

[0026] Icon: Rotor 1, wall surface 2, labyrinth teeth 3, labyrinth slot 4, cavity 5, swirl device 6. Specific embodiments

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0028] Embodiment

[0029] Combined with Figures 3 to 7 As shown, this embodiment provides a labyrinth seal structure that enhances the sealing performance through inlet pre-whirl and inter-stage pre-whirl. A swirl device 6 is provided in front of the labyrinth slot 4 to generate a tangential component of the airflow, decomposing the axial kinetic energy into axial and tangential components, thereby reducing the axial kinetic energy and strengthening the sealing characteristics.

[0030] For labyrinth sealing, its working principle is to set a sudden contraction flow channel (labyrinth slot 4) and a sudden expansion flow channel (cavity 5) in the channel, and utilize the acceleration effect of the labyrinth slot 4 and the flow separation and backflow induced by the sudden expansion of the flow channel at high speeds to generate total pressure loss and throttling effect, thereby reducing the leakage amount of the airflow. Taking the rotating labyrinth seal as an example:

[0031] Existing research shows that at the same inlet and outlet total-static pressure ratio, the leakage amount of the rotating labyrinth seal decreases as the inlet swirl ratio increases. The definition of the swirl ratio is as follows:

[0032]

[0033] Wherein, is the tangential velocity of the airflow, ω is the angular velocity of the rotation of the labyrinth teeth, and r 2 is the radius at the tip position of the labyrinth teeth. As in the special case Figure 6 shown, in this special case, V y is equal to The basic principle is that the flow rate through the labyrinth slot is proportional to the axial velocity of the airflow, as shown in the following formula:

[0034] q m = ρAV x

[0035] Wherein, q m is the leakage flow rate, ρ is the density of the airflow, A is the area of the labyrinth slot, and Vx is the axial velocity component of the air flow. Obviously, at the same total-static pressure ratio at the inlet and outlet, the axial velocity component (V x = Vcosθ) of the incoming flow with pre-rotation is less than the axial velocity component (V x = V) of the air flow without pre-rotation. Figure 6 A brief description of the principle of the pre-rotation effect is given. Therefore, at the same total-static pressure ratio at the inlet and outlet, the leakage flow rate of the labyrinth seal decreases with the increase of the inlet swirl ratio.

[0036] The existing labyrinth seal passively accepts the pre-rotation effect of the incoming flow, and its accompanying pre-rotation effect is given by the upstream components. For example, the rotating component gives the air flow a tangential component through wall friction.

[0037] Based on this idea, in this embodiment, the pre-rotation effect is generated by setting the swirl device 6, so that the air flow passing through the labyrinth slot 4 deflects, thereby decomposing the axial kinetic energy into an axial component and a tangential component, and further reducing the ventilation effect of the labyrinth slot 4, and further enhancing the sealing performance.

[0038] Specifically, in this embodiment, as Figure 3 and Figure 4 shown, the labyrinth teeth 3 and the wall surface 2 form the labyrinth slot 4; a first swirl device 6 is arranged upstream of the inlet of the first labyrinth slot 4 on the wall surface 2, and the same swirl device 6 is also arranged between the subsequent labyrinth teeth 3 and the labyrinth teeth 3. Of course, in other embodiments, the swirl device 6 can be arranged alone upstream of the first labyrinth slot, or between two labyrinth teeth, or arranged in a combined manner, that is, the swirl device 6 is arranged between every two of the multiple labyrinth teeth 3 upstream and downstream of the first labyrinth tooth 3, as Figure 7 shown, some examples of combined pre-rotation are given.

[0039] The swirl device 6 includes an end face for being installed on the installation groove on the peripheral wall of the intake passage, and pre-rotation vanes are arranged on the end face. As Figure 5 shown, the pre-rotation vanes can be a cascade or fins with baffles or baffle plates. Of course, the pre-rotation vanes can also be other shapes, which are not specifically limited here, but no matter what kind of design, it must be able to restrict the air flow acceleration. When using a cascade to generate pre-rotation, it should be ensured that the inlet and outlet areas of the cascade channels are almost equal to reduce the additional ventilation effect caused by the air flow acceleration. At the same time, it should be noted that different-shaped pre-rotation vanes can be used in combination. For example, when the swirl device 6 is arranged between every two of the multiple labyrinth teeth 3 upstream and downstream of the first labyrinth tooth, the pre-rotation vanes can be any combination between a cascade or fins with baffles or baffle plates.

[0040] AsFigure 5 As shown, the cyclone device 6 decomposes the kinetic energy along the axis into an axial component and a tangential component thereby reducing the axial kinetic energy. The reduction of the axial momentum weakens the ventilation effect of the labyrinth seal, thereby enhancing the sealing performance.

[0041] In this embodiment, the height of the cyclone device 6 is slightly greater than the clearance of the labyrinth slit 4, or the minimum height given according to the processing level, so as to ensure that the cyclone device 6 does not overly intrude into the cavity formed by the labyrinth 3 and the wall surface 2, thereby ensuring the total pressure loss induced by the geometric sudden expansion to the greatest extent.

[0042] In this embodiment, for the rotating labyrinth, the rotating component can impart a certain tangential component to the air flow through wall friction. The direction of this tangential component may be opposite to the preset tangential component, weakening the pre-whirl effect. Therefore, for the rotating labyrinth, the best design method is that the tangential component imparted by the rotating component is superimposed on the tangential component imparted by the cyclone device 6. Therefore, in order to ensure the pre-whirl effect, for the rotating labyrinth, the cyclone device 6 is arranged on the stationary wall surface 2 and does not rotate with the rotor 1. It should be noted that for the rotating labyrinth seal, the cyclone device 6 is arranged on the stationary wall surface upstream of the labyrinth slit, rather than on the rotor 1, that is, the introduced cyclone device 6 does not rotate with the rotor 1 to achieve the maximum pre-whirl effect, and it can adopt a positive pre-whirl or reverse pre-whirl design.

[0043] The cyclone device 6 is of an annular structure, which includes an annular end face for being installed on the installation groove on the peripheral wall of the intake passage. A whole circle of pre-whirl small blades is arranged on the annular end face; of course, the pre-whirl small blades can also be assembled by multiple modules.

[0044] After introducing the cyclone device 6 in this embodiment, the total pressure loss induced by the geometric sudden expansion can be retained to the greatest extent. At the same time, the cyclone device 6 can induce additional total pressure loss, and this part of the total pressure loss is mainly faced to the fluid layer close to the upper wall surface. The streamline of this part of the air flow is roughly parallel to the upper wall surface and is hardly affected by the geometric sudden expansion. Therefore, the total pressure loss induced by the cyclone device 6 can be superimposed on the total pressure loss induced by the geometric sudden expansion to enhance the sealing characteristics.

[0045] The above is only the preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions within the idea of the present invention belong to the protection scope of the present invention.

[0046] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0047] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, the meaning of "a plurality" is two or more unless otherwise specifically defined.

[0048] In the present invention, unless otherwise clearly defined and limited, the terms such as "mounted", "connected", "coupled", "fixed", etc. shall be construed in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the internal communication of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0049] In the present invention, unless otherwise clearly defined and limited, the first feature being "on" or "under" the second feature may include the direct contact between the first and second features, or may include the situation where the first and second features are not in direct contact but in contact through other features therebetween. Moreover, the first feature being "above", "over" and "on top of" the second feature includes that the first feature is directly above and obliquely above the second feature, or merely means that the horizontal height of the first feature is higher than that of the second feature. The first feature being "under", "beneath" and "underneath" the second feature includes that the first feature is directly below and obliquely below the second feature, or merely means that the horizontal height of the first feature is lower than that of the second feature.

Claims

1. A comb tooth sealing structure that enhances sealing performance through inlet pre-swirl and inter-stage pre-swirl, characterized in that: A swirl device is arranged in front of the grate teeth slits to make the airflow produce a tangential component, decomposing the axial kinetic energy into an axial component and a tangential component, thereby reducing the axial kinetic energy and enhancing the sealing characteristics.

2. The comb tooth sealing structure for enhancing sealing performance by inlet pre-swirl and inter-stage pre-swirl according to claim 1, characterized in that: The height of the swirl device is slightly larger than the gap of the grate teeth slit, or the minimum height given according to the processing level, to ensure that the swirl device does not excessively invade the cavity formed by the grate teeth and the wall surface, thereby maximizing the total pressure loss induced by the geometric sudden expansion.

3. The comb tooth sealing structure with enhanced sealing performance through inlet pre-swirl and inter-stage pre-swirl according to claim 1, characterized in that: The swirl device is arranged upstream of the grate tooth slit or between two grate teeth, or any combination of the two.

4. The comb tooth sealing structure with enhanced sealing performance through inlet pre-swirl and inter-stage pre-swirl according to claim 1, characterized in that: For the rotating grate seal, the swirl device is arranged on a stationary wall surface and does not rotate with the rotor.

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