Active Foil Air Film Sealing Structure Based on Electromagnetic Induction

Abstract

The present invention discloses an active foil air film sealing structure based on electromagnetic induction, which includes a stator assembly and a rotor assembly. The stator assembly includes a sealing cavity, and one end of the sealing cavity is connected to a pressing end cover; it also includes a plurality of split sealing units and an elastic sealing assembly located on the inner wall of the sealing cavity; the rotor assembly is located inside the elastic sealing assembly, a dynamic pressure groove is formed on the rotor assembly, and there is a gap between the rotor assembly and the elastic sealing assembly; the active control assembly includes a first magnetic part located on the outer wall of the split sealing unit, a piezoelectric crystal located outside the split sealing unit, and a second magnetic part located on the piezoelectric crystal. The first magnetic part and the second magnetic part are magnetically repulsive and have a gap. The present invention improves the anti-collision and abrasion impact performance and the self-adaptive ability, so as to solve the problem that the active control method for cylindrical surface sealing in the prior art has an unsatisfactory control effect, and achieves the purpose of improving the active control precision and accuracy of the cylindrical surface sealing unit.

Description

Technical Field

[0001] The present invention relates to the technical field of cylindrical seals, and particularly to an active foil gas film seal structure based on electromagnetic induction. Background Art

[0002] Cylindrical gas film seal is a new type of shaft end seal form, and its working principle is similar to that of a gas radial bearing. As the rotor drives the sleeve to rotate, the dynamic pressure grooves of the sleeve and the eccentric structure of the seal act together. The high-pressure isolation gas on the outer diameter side is pumped into the space between the cylindrical surfaces of the seal under the action of viscous shear force. Due to the dynamic pressure effect, the gas film pressure gradually rises from the pressure inlet to the root diameter of the dynamic pressure groove, and reaches the maximum value at the root diameter of the groove. Subsequently, the sealed gas flows from the root diameter of the groove to the pressure outlet. Due to the step effect, energy dissipation occurs when the sealed gas flows through the dam area, resulting in a rapid decrease in the gas film pressure. The increase in the film pressure on the cylindrical surface makes the formed lifting force increase, forcing the two interfaces to always be in a stable non-contact state. At the same time, when the sealing medium is pumped into the dynamic pressure groove, during this process, due to the effect of eccentricity, the sealing medium is compressed. Relying on the dynamic pressure grooves opened on the outer surface of the sleeve and the wedge-shaped gap formed by the eccentricity between the floating ring and the sleeve, the gas film in the sealing gap is distributed in a wedge-shaped convergent manner. The combined action of the two produces a hydrodynamic pressure effect, resulting in an increase in the gas pressure in the gap. When the operation is stable, a micron-level gas lubrication film is formed between the floating ring and the sleeve, and the medium is blocked by the gas lubrication film in the main leakage channel to achieve the sealing effect.

[0003] Compared with the end face gas film seal, the main advantage of the cylindrical gas film seal is its better flexible floating property, which allows a larger radial displacement. However, when the cylindrical seal is applied to high-speed rotating machinery, especially in the aerospace field, the existing sealing technology has obvious limitations, which are mainly manifested in the following aspects:

[0004] First, most of the existing cylindrical seal technologies are passive control design methods and cannot respond to changes in actual working conditions and service environments during the operation of the unit. This passive control design method and operation mode greatly weaken the ability to regulate the sealing performance and become inapplicable when an aircraft is operating under complex and changeable working conditions.

[0005] Second, due to the fluid excitation in the microchannel under the conditions of high speed or variable attitude operation of an aircraft, the cylindrical seal system will frequently experience non-linear shaft vibration. Moreover, the thickness of the sealed gas film is generally only a few micrometers. Even when the gas film stiffness is very large, it is impossible to cope with the threats of large radial swings of the rotating shaft and contact friction and wear caused by large vibration displacements of the rotor.

[0006] Thirdly, during the operation of an aircraft, even minor changes in the airframe can induce instability. Meanwhile, when the sealing medium coexists in different phases, it is more vulnerable to the random uncertainty excitation caused by environmental factors and its own structure, which can lead to rubbing and generate contact dry friction self-excited oscillatory vibration, resulting in seal failure, reduced mechanical working efficiency, and affecting the operation of the entire machine.

[0007] Fourthly, most of the seal pairs in the existing cylindrical seal technology adopt a "rigid" to "rigid" matching mode, which has low inclusiveness and aggravates the harm caused by direct rubbing to a certain extent.

[0008] Therefore, the existing cylindrical seal technology is difficult to be directly applied to high-speed rotating machinery, especially the shaft-end seal of aerospace aircraft. Thus, it is necessary to explore a new seal technology with good comprehensive seal performance, excellent anti-rubbing and impact resistance, and capable of achieving active control and condition monitoring. In response to the above problems, the inventor team has made certain attempts and proposed "A Floating Elastic Foil Seal Structure with Fluid-Induced Separation" (Application No.: CN202210132305.2; Publication No.: CN115313730A). This structure aims to increase the gas film lifting force and improve the seal performance by proposing a combined foil seal structure that can achieve fluid-induced separation, and solve the problems of poor inclusiveness and insufficient applicability in the existing seal technology. Subsequently, "An Active Cylindrical Seal Structure for Aircraft" (Application No. 202210816592.9; Publication No.: CN115046012A) was proposed. This structure innovatively applies piezoelectric ceramics to the seal field, realizing the active control of seal operation and improving the applicability of cylindrical seal technology. However, with the further in-depth research, the inventors of this solution found that the above structures have problems such as narrow application range and unsatisfactory control effect. Specifically, although "A Floating Elastic Foil Seal Structure with Fluid-Induced Separation" improves the seal performance through fluid-induced separation, the flow direction of its wave foil must be consistent with the rotation direction of the rotating shaft to increase the gas film lifting force. Therefore, the installation requirements are relatively high, and there are problems such as abnormal shutdown and sudden reverse rotation of the rotating shaft in the field of aerospace aircraft. This structure has poor applicability to sudden changes in operating conditions; "An Active Cylindrical Seal Structure for Aircraft" introduces piezoelectric ceramics into the seal field and realizes the active control operation of the seal. However, the installation method of this structure has certain limitations. The main reason is that the piezoelectric ceramics are evenly distributed along the circumferential direction on the seal cavity, while the change of the seal gap occurs along the radial direction. Therefore, the deformation response of the piezoelectric ceramics to specific operating conditions will be affected to a certain extent by this unreasonable installation method, that is, when the deformation of the piezoelectric ceramics acts on the radial seal gap, there is loss in the circumferential direction, which has a huge impact on micro displacements. Summary of the Invention

[0009] The present invention provides an active foil gas film seal structure based on electromagnetic induction to solve the problems existing in the cylindrical seal unit at the shaft end of high-speed rotating machinery in the prior art, such as passive control during operation, large vibration displacement of the rotor-seal system leading to contact friction and wear, and losses in the circumferential direction when the deformation of piezoelectric ceramics acts on the radial seal clearance. The active control of the seal unit is realized, the seal clearance is adjustable, the seal unit is ensured to operate in the best working state, and at the same time, the anti-collision and abrasion impact performance is improved, the adaptability is enhanced, and the huge interference caused by circumferential losses to the radial seal clearance is avoided.

[0010] The present invention is realized through the following technical solutions:

[0011] The active foil gas film seal structure based on electromagnetic induction includes a stator assembly and a rotor assembly. The stator assembly includes a seal cavity and a pressing end cover detachably connected to one end of the seal cavity;

[0012] It further includes a plurality of split seal units evenly distributed along the circumferential direction on the inner wall side of the seal cavity and an elastic seal assembly on the inner diameter side of the split seal units;

[0013] The rotor assembly is eccentrically installed on the radial inner side of the elastic seal assembly. A plurality of dynamic pressure grooves are formed on the rotor assembly and evenly distributed along the annular direction, and there is a gap between the rotor assembly and the elastic seal assembly;

[0014] It further includes a plurality of active control components. The active control components include a first magnetic member on the outer wall of the split seal unit, a piezoelectric crystal on the outside of the split seal unit, and a second magnetic member on the piezoelectric crystal. The first magnetic member and the second magnetic member are magnetically repulsive and have a gap.

[0015] In view of the defect that the active control method of the cylindrical seal in the prior art has an unsatisfactory control effect, the inventor of this case found in the continuous in-depth research process that one of the factors affecting the control effect is that: the thickness of the gas film gap of the cylindrical seal is generally in the micron range, so the deformation amount for its active control is also only in the micron range. In the prior art, the deformation of the piezoelectric ceramics is transmitted by the support member, and the support member needs to be in contact with both the piezoelectric ceramics and the floating component at the same time. The friction loss between the contact positions and the deformation of the support member itself will cause a large amount of energy loss in the process of transmitting the deformation of the piezoelectric ceramics to the floating component, and further make it difficult to accurately control the force exerted on the floating component and result in poor adjustment accuracy of the seal clearance. The present application is an invention created based on the discovery of the above technical problems.

[0016] Specifically, the stator assembly, rotor assembly, sealed cavity, compression end cover, etc. in this application are all prior arts and will not be elaborated here. This application uses the sealed cavity as the main structure of the stator assembly. A number of split-type sealing units are installed on the inner wall of the sealed cavity, and an elastic sealing component is installed inside the split-type sealing unit. The high-pressure medium gas flows into the sealing structure from the end where the dynamic pressure groove is opened. Due to the rotation of the rotor assembly, under the dual action of the convergent wedge effect brought by eccentric installation and the dynamic pressure wedge effect brought by fluid viscosity, a pressurized fluid film is formed, and the maximum pressure is reached at the root diameter part of the dynamic pressure groove, so that a certain gap is always maintained between the rotor assembly and the elastic sealing component, thereby realizing non-contact sealing.

[0017] This application is provided with a number of active control components. By means of the active control components, the radial position of the split-type sealing unit is changed, and the internal elastic sealing component is driven by the split-type sealing unit to generate deformation, thereby changing the shape of the gas film. The shape of the gas film will directly affect the sealing performance and system stability. Therefore, this application realizes the active control operation of the sealing unit, enables the sealing gap to be adjustable, thus significantly increasing the wedge space of the gas lubrication film, weakening the cross-coupling effect, enhancing the dynamic pressure effect, and being conducive to ensuring that the sealing unit operates in the best working state. Moreover, this application can optimize and regulate the sealing performance in real time, thereby preventing abnormal vibration shocks, frictional wear induced by uncertain excitations during the working process, and also avoiding the instability of the sealing system caused by sudden changes in the operating state, and greatly improving the anti-interference ability of the cylindrical gas seal.

[0018] The active control components in this application adopt non-contact magnetic control. A first magnetic part is arranged on the outer surface of the split-type sealing unit, and a second magnetic part that is magnetically repulsive to the first magnetic part and does not directly contact it is arranged. The action of the second magnetic part is controlled by a piezoelectric crystal, and then the relative position between the second magnetic part and the first magnetic part is changed, so as to adjust the magnetic field strength received by the first magnetic part, and further adjust the force received by the split-type sealing unit, realizing the adjustment of the gas film gap.

[0019] Compared with the prior art, the present application has the following advantages: (1) Instead of using axially distributed floating components, a circumferentially distributed split seal unit is used as the adjustment structure for the gas film gap. There is no need to open an air inlet hole on the sealing cavity for intermediate air intake, and air intake sealing can be achieved from the axial end, making it applicable to a wider range of working conditions; (2) A non-contact method is used to apply a force from the outside to the inside towards the split seal unit, eliminating the problems of large losses and low precision caused by the direct contact method for transmitting deformation in the prior art. Since there is no longer the self-deformation of the support member and the friction loss at multiple contact positions, the control precision of the active control component can be significantly improved, thereby improving the active control precision and accuracy of the cylindrical seal unit; (3) The direction of the seal gap is kept consistent with the direction of the controlled deformation, avoiding unnecessary losses in the deformation of the piezoelectric crystal and ensuring precise control of the seal gap at the micron level. Moreover, the combination of the split seal unit and the elastic seal component realizes a large-flexibility structure, providing a larger change in the seal gap when friction, wear, impact, and vibration occur; the bottom end of the piezoelectric crystal is non-contact with the flexible seal unit, and through the change in the magnetic field generated by the change in current, electromagnetic conversion is achieved to promote the change of the seal gap; finally, this structure can, according to the actual operation changes of the seal, transmit electrical signals to the external monitoring system, and in a certain sense, a new seal that combines active control and condition monitoring can be realized.

[0020] Further, the piezoelectric crystal includes a metal rod and piezoelectric ceramics coated outside the metal rod, and the second magnetic member is installed at the end of the metal rod.

[0021] In the prior art, piezoelectric ceramics are simply used to achieve active control. However, the inventor found during the research process that when the existing piezoelectric ceramics are relatively small in volume, their movement range is very small. Although a flexible hinge can be used to amplify the micro-displacement, its conduction loss still restricts the development. The gas film gap to be controlled in the present application is at the micron level, but this also requires relatively large-volume piezoelectric ceramics to achieve, which restricts both the miniaturization of the sealing equipment and the cost. Based on this, this solution creatively designs a unique piezoelectric crystal, with piezoelectric ceramics coated outside the metal rod. The internal metal rod is used as a micro-displacement amplification mechanism with a simple structure and regular shape, which can significantly amplify and transmit small displacements. It has the advantages of small volume, no mechanical friction, compact structure, high movement sensitivity, stable operation, and lubrication-free. In this solution, the use of the metal rod can magnify the tiny mechanical deformation of the small-volume piezoelectric ceramics from a few microns to dozens or even hundreds of microns, and then transmit this displacement to the second magnetic member, thereby changing the magnetic field between the second magnetic member and the first magnetic member to achieve the desired effect. When it is necessary to adjust the position of the elastic seal component, different electrical signals can be applied to the piezoelectric ceramics as needed.

[0022] When stable and not affected by external electrical signals, mechanical deformations, etc., a stable non-contact state is maintained between the first magnetic member and the second magnetic member. During the control process, the voltage applied to the piezoelectric ceramic can act on the metal rod simultaneously, generating an instantaneous current in the metal rod, and then generating an electromagnetic field based on electromagnetic induction. This electromagnetic field disrupts the balance between the first magnetic member and the second magnetic member, forcing relative movement between the two to quickly reach the next dynamic balance.

[0023] In addition, during the start-stop stage of sealed operation, axial vibration will exacerbate the effects of friction wear and vibration shock, causing changes in the flow field. After the flow field changes, the elastic sealing assembly deforms under force, driving the split sealing unit to vibrate or displace, causing the first magnetic member installed thereon to vibrate or displace. During this process, the metal rod cuts the magnetic induction lines and generates a small electrical signal based on the principle of electromagnetic induction. The user can analyze the internal vibration and displacement conditions based on this electrical signal and use it as a feedback signal to more accurately adjust the control voltage applied to the piezoelectric ceramic.

[0024] Therefore, the piezoelectric crystal in this solution: (1) can effectively amplify the micro-displacement of the piezoelectric ceramic to achieve more precise active control; (2) can use electromagnetic induction to force the first magnetic member and the second magnetic member to reach the next dynamic balance faster, thereby improving the efficiency and accuracy of active control of the split sealing unit; (3) can sensitively sense small changes in the flow field and transmit this small change through an electrical signal, significantly enriching the real-time monitoring ability of the cylindrical seal performance and improving the visualization feedback means, realizing an active positive feedback and intelligent regulation of "voltage - sealing performance - voltage - sealing performance...".

[0025] Furthermore, the metal rod includes a large-diameter section and a small-diameter section, and the large-diameter section and the small-diameter section are coaxial; the piezoelectric ceramic is coated outside the small-diameter section, and the outer diameter of the piezoelectric ceramic is equal to the outer diameter of the large-diameter section, and the second magnetic member is installed at the end of the large-diameter section away from the small-diameter section.

[0026] A plurality of mounting holes opposite to the first magnetic member are provided on the sealing cavity along the circumferential direction. The piezoelectric crystal is located in the mounting holes, and the hole wall of the mounting hole is sealed with the metal rod and / or the piezoelectric ceramic through a sealing ring.

[0027] The metal rod in this solution has a variable-diameter structure, which at least includes two parts with different outer diameters, respectively defined as a large-diameter section and a small-diameter section. Among them, the piezoelectric ceramic is coated outside the small-diameter section, and the outer diameter of the piezoelectric ceramic is equal to the outer diameter of the large-diameter section, making the entire piezoelectric crystal structure regular and stable, facilitating assembly. At the same time, this structure enables the external electrical signal to act on the piezoelectric ceramic without deforming in the circumferential and axial directions, only generating movement in the radial direction, without displacement loss, and avoiding the displacement offset phenomenon in the multi-contact state.

[0028] Further, a plurality of circumferentially distributed grooves are formed on the inner wall of the sealed cavity, and the split seal unit is installed in the grooves; an axial slot is formed between two adjacent grooves, and the axial slot is used for installing an elastic seal assembly.

[0029] Further, the elastic seal assembly includes a circumferential flat foil and a split corrugated foil located outside the circumferential flat foil; the circumferential flat foil and the split corrugated foil are in contact with each other.

[0030] In this solution, along the radial direction, the outer wall of the circumferential flat foil is in contact with the inner end of the split corrugated foil, and the split corrugated foil is clamped between the circumferential flat foil and the split seal unit. Coulomb friction will occur between the split corrugated foil and the circumferential flat foil and the split seal unit. Due to the load acting on the surface of the circumferential flat foil and the Coulomb friction between the circumferential flat foil and the split corrugated foil, the entire elastic seal assembly can undergo small deformations in both the radial and circumferential directions, realizing real-time control and adaptive adjustment, thereby fully ensuring the stability of the seal.

[0031] Further, the two circumferential ends of the split corrugated foil are respectively a fixed end and a separation boundary;

[0032] The fixed end is fixedly installed on the sealed cavity through the axial slot;

[0033] A plurality of separation gaps are formed on the split corrugated foil starting from the separation boundary, and the separation gaps are perpendicular to the separation boundary.

[0034] In this solution, the separation boundary is the free end of the split corrugated foil. For each corrugated foil, a plurality of separation gaps are formed starting from the separation boundary, so that each separation gap is perpendicular to the separation boundary, and the separation gaps do not completely penetrate the single corrugated foil, so that each corrugated foil still maintains an integral structure at the fixed end, which can prevent unnecessary deformation of the foil under large temperature fluctuations.

[0035] Further, an extension portion extending in the outer diameter direction is provided at one end of the circumferential flat foil close to the high-pressure side of the seal, and the extension portion is clamped and fixed between the sealed cavity and the pressing end cover.

[0036] In this solution, the extension portion is located on the high-pressure side of the seal and extends radially outward. Therefore, it can be equivalently understood as a flanging structure. The extension portion is positioned before connecting the sealed cavity and the end cover, so that after the sealed cavity and the end cover are connected, the extension portion is stably clamped and pressed between the two, thereby fully ensuring the integrity of the sealing surface.

[0037] Furthermore, the rotor assembly includes a rotating shaft eccentrically passing through the sealing cavity and a sleeve fixedly sleeved outside the rotating shaft; a plurality of dynamic pressure grooves are annularly and uniformly distributed on the outer wall of the sleeve, and the dynamic pressure grooves extend to the end face of the sleeve facing the high-pressure side of the seal.

[0038] Through the flexible support design of the elastic seal assembly, the offset or runout of the rotor assembly in the radial direction can be accommodated, and at the same time, it plays a role in compensating and balancing the inevitable machining errors and installation errors, ensuring that the elastic seal assembly and the sleeve always remain in a non-contact state, and greatly improving the anti-vibration interference ability of the cylindrical gas seal.

[0039] Furthermore, an annular seal groove is provided inside the pressing end cover, a sealing gasket is placed in the annular seal groove, and the pressing end cover and the sealing cavity are connected by set bolts. Under the action of the bolt pre-tightening force, the sealing gasket can be pressed, thereby better improving the sealing performance.

[0040] Compared with the prior art, the present invention has at least the following advantages and beneficial effects:

[0041] 1. The active foil gas film seal structure of the present invention based on electromagnetic induction, in which the active control component adopts non-contact magnetic control, no longer uses axially distributed floating components, but uses circumferentially distributed split seal units as the adjustment structure of the gas film gap, and there is no need to open air inlet holes on the sealing cavity for intermediate air inlet, and air inlet sealing can be realized from the axial end, and the applicable working conditions are wider.

[0042] 2. The active foil gas film seal structure of the present invention based on electromagnetic induction applies force from the outside to the inside to the split seal unit in a non-contact manner, abandoning the problems of large loss and low precision caused by the direct contact method used in the prior art to transmit deformation. Since there is no longer the self-deformation of the support and the friction loss at multiple contact positions, the control precision of the active control component can be significantly improved, and then the active control precision and accuracy of the cylindrical seal unit can be improved. When an external electrical signal acts on the piezoelectric ceramic, it will not deform in the circumferential and axial directions, but only move in the radial direction, without displacement loss, and at the same time, the offset phenomenon of displacement in the multi-contact state is avoided.

[0043] 3. The active foil gas film seal structure based on electromagnetic induction of the present invention uses a unique piezoelectric crystal, which can significantly amplify and transmit small displacements. It can magnify the tiny mechanical deformation of a small-volume piezoelectric ceramic from a few micrometers to dozens or even hundreds of micrometers. By using a new combined piezoelectric crystal and radially installing it along the circumferential direction on the sealing cavity, the deformation and the regulation of the sealing gap are in the same direction, and the displacement change is more obvious. A groove is opened on the inner side of the sealing cavity and a sealing unit is installed, which is combined with an elastic sealing component to form a large flexible structure. When friction, wear, impact, and vibration occur, a larger change in the sealing gap is provided. The bottom end of the piezoelectric crystal is non-contact with the flexible sealing unit, and through the magnetic field change generated by the current change, electromagnetic conversion is achieved to promote the change of the sealing gap. Finally, this structure can, according to the actual operation changes of the seal, transmit electrical signals to the external monitoring system, and to a certain extent, achieve a new seal that combines active control and condition monitoring.

[0044] 4. In the active foil gas film seal structure based on electromagnetic induction of the present invention, the piezoelectric crystal can use electromagnetic induction to force the first magnetic part and the second magnetic part to reach the next dynamic equilibrium faster, thereby improving the efficiency and accuracy of the active control of the split seal unit.

[0045] 5. The active foil gas film seal structure based on electromagnetic induction of the present invention can sensitively sense the tiny changes in the flow field and transmit this tiny change through electrical signals, significantly enriching the real-time monitoring ability of the cylindrical seal performance and improving the visualization feedback means, realizing an active good feedback and intelligent regulation of "voltage - sealing performance - voltage - sealing performance...". BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, form a part of this application, and do not limit the embodiments of the present invention. In the drawings:

[0047] Figure 1 is an exploded view of a specific embodiment of the present invention;

[0048] Figure 2 is a cross-sectional view of a specific embodiment of the present invention;

[0049] Figure 3 is a schematic structural view of a specific embodiment of the present invention with a partial cut-away;

[0050] Figure 4 is a schematic structural view of the sealing cavity in a specific embodiment of the present invention;

[0051] Figure 5 is a schematic structural view of the pressing end cover in a specific embodiment of the present invention;

[0052] Figure 6 Schematic diagram of the structure of the bushing in a specific embodiment of the present invention;

[0053] Figure 7 Schematic diagram of the structure of the integral flat foil in a specific embodiment of the present invention;

[0054] Figure 8 Schematic diagram of the structure of the split wave foil in a specific embodiment of the present invention;

[0055] Figure 9 Schematic diagram of the structure of the split sealing unit in a specific embodiment of the present invention;

[0056] Figure 10 Schematic diagram of the structure of the active control component in a specific embodiment of the present invention;

[0057] Figure 11 Schematic diagram of the structure of the piezoelectric crystal in a specific embodiment of the present invention.

[0058] Marks in the drawings and corresponding names of parts:

[0059] 1 - Sealing cavity, 11 - Mounting hole, 12 - Positioning groove, 13 - Groove, 14 - Axial slot, 15 - Set bolt mounting hole; 2 - Compression end cover, 21 - Annular sealing groove, 22 - Through hole, 23 - Sealing gasket; 3 - Rotating shaft; 4 - Bushing, 41 - Hydrodynamic groove; 5 - Integral flat foil, 51 - Extension; 6 - Split wave foil, 61 - Fixed end, 62 - Separation gap, 63 - Separation boundary; 7 - Split sealing unit; 8 - Metal rod; 9 - Piezoelectric ceramic; 71 - First magnetic part; 81 - Second magnetic part; 200 - Set bolt. Specific embodiments

[0060] To make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with the embodiments and the drawings. The illustrative embodiments and descriptions thereof of the present invention are only used to explain the present invention and are not intended to limit the present invention. In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "front", "rear", "left", "right", "up", "down", "vertical", "horizontal", "high", "low", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and 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 limiting the protection scope of the present application.

[0061] Embodiment 1:

[0062] As Figures 1 to 3The active foil gas film sealing structure based on electromagnetic induction shown in the figure includes a stator assembly and a rotor assembly. The stator assembly includes a sealing cavity 1 and a pressing end cover 2 detachably connected to one end of the sealing cavity 1.

[0063] It further includes a plurality of split sealing units 7 on the inner wall of the sealing cavity 1 and an elastic sealing assembly on the inner diameter side of the split sealing units 7.

[0064] The rotor assembly is eccentrically installed inside the elastic sealing assembly. A plurality of dynamic pressure grooves 41 are evenly distributed in the circumferential direction on the rotor assembly, and there is a gap between the rotor assembly and the elastic sealing assembly.

[0065] The rotor assembly includes a rotating shaft 3 eccentrically passing through the sealing cavity 1 and a shaft sleeve 4 fixedly sleeved outside the rotating shaft 3. A plurality of dynamic pressure grooves 41 are evenly distributed in a ring on the outer wall of the shaft sleeve 4, and the dynamic pressure grooves 41 extend to the end face of the shaft sleeve 4 facing the high-pressure sealing side.

[0066] It further includes a plurality of active control components. The active control components include a first magnetic member 71 on the outer wall of the split sealing unit 7, a piezoelectric crystal outside the split sealing unit 7, and a second magnetic member 81 on the piezoelectric crystal. The first magnetic member 71 and the second magnetic member 81 are magnetically repulsive and have a gap.

[0067] As Figure 10 、 Figure 11 shown, the piezoelectric crystal includes a metal rod 8 and a piezoelectric ceramic 9 coated outside the metal rod 8. The second magnetic member 81 is installed at the end of the metal rod 8.

[0068] The metal rod 8 includes a large-diameter section and a small-diameter section, and the large-diameter section and the small-diameter section are coaxial. The piezoelectric ceramic 9 is coated outside the small-diameter section, and the outer diameter of the piezoelectric ceramic 9 is equal to the outer diameter of the large-diameter section. The second magnetic member 81 is installed at the end of the large-diameter section away from the small-diameter section. A plurality of installation holes 11 opposite to the first magnetic member 71 are opened in the circumferential direction on the sealing cavity 1. The piezoelectric crystal is located in the installation holes 11, and the hole wall of the installation holes 11 and the metal rod 8 and / or the piezoelectric ceramic 9 are sealed by a sealing ring.

[0069] In this embodiment, the shaft sleeve 4 and the rotating shaft 3 are in interference fit.

[0070] In this embodiment, the dynamic pressure grooves 41 can be in the forms of spiral grooves, straight grooves, T-shaped grooves, etc. This embodiment does not limit the groove type of the dynamic pressure grooves 41.

[0071] Preferably, the groove depth of the dynamic pressure grooves 41 is 3 - 10 μm.

[0072] Those skilled in the art should understand that in the sealing structure of the present application along the axial direction, one end is the high-pressure end and the other end is the low-pressure end. During operation, the high-pressure medium gas needs to flow into the dynamic pressure groove of the seal from the high-pressure end. Therefore, in this solution, the dynamic pressure groove is extended to the end face of the high-pressure end of the shaft sleeve, that is, the dynamic pressure groove is opened starting from the high-pressure end face of the shaft sleeve, so that the dynamic pressure groove is in an open state at the high-pressure end face of the shaft sleeve to facilitate the rapid entry of high-pressure fluid.

[0073] In this embodiment, the relative position between the elastic sealing assembly and the shaft sleeve can be adjusted through the active control assembly. The change in the position of the elastic sealing assembly will directly determine the shape of the fluid film, and the shape of the fluid film will also directly affect the sealing performance and the stability of the rotor system. This structure can realize the real-time active control of the sealing unit, further improve the flow field characteristics, thereby preventing abnormal vibration shocks, frictional wear induced by uncertain excitations during operation, avoiding the instability of the sealing system caused by sudden changes in the operating state, overcoming the problems of uneven collisions and wear caused by multi-posture operating modes, realizing the active regulation of the sealing performance, and significantly improving the applicability of the cylindrical surface sealing technology in this field. Specifically:

[0074] When the sealing structure of this embodiment is operating normally, the high-pressure medium gas flows into the sealing structure from the end where the dynamic pressure groove is opened. Due to the rotation of the rotor assembly, under the dual action of the convergence wedge effect brought by eccentric installation and the dynamic pressure wedge effect brought by fluid viscosity, a pressurized fluid film is formed, and the maximum pressure is reached at the root diameter part of the dynamic pressure groove. Under the combined action of the wedge effect and the dynamic pressure effect, a certain gap is always maintained between the rotor assembly and the elastic sealing assembly, thereby realizing the blocking of the main leakage channel.

[0075] The first magnetic member 71 and the second magnetic member 81 in this embodiment are both magnetic sheets.

[0076] When stable, without the influence of external electrical signals, mechanical deformation, etc., a stable non-contact state is maintained between the two magnetic sheets. When an external input current acts on the metal rod, due to the influence of electromagnetic induction, a magnetic field will be generated in the area near the magnetic sheet at the tail end of the metal rod. The magnetic field destroys the balance between the two magnetic sheets, forcing relative movement between them to reach the next dynamic balance.

[0077] The micro-displacement generated when the electrical signal acts on the piezoelectric ceramic is amplified by the metal rod and transmitted between the two magnetic plates, causing it to push the sealing unit to deform and move, further affecting the elastic sealing component and causing it to deform appropriately. The change in the position of the elastic sealing component will directly determine the shape of the air film, and the shape of the air film will also directly affect the sealing performance and system stability. Therefore, this solution improves the flow field characteristics in real time through this "electrical signal-mechanical deformation-force-displacement" transmission process, thereby preventing abnormal vibration impact and friction wear induced by uncertain excitation during operation, and avoiding instability of the sealing system caused by sudden changes in operating conditions.

[0078] At the same time, the use of piezoelectric ceramics in this solution also has the following advantages: Due to the sensitive characteristics of piezoelectric ceramics, extremely weak mechanical vibrations can be converted into electrical signals. During the start-stop phase of the sealing operation, axial vibration will aggravate the impact of friction, wear and vibration shock, causing changes in the flow field. Piezoelectric ceramics can sensitively sense slight changes in the flow field and transmit these slight changes through electrical signals, which enriches the real-time monitoring and visualization of cylindrical sealing performance, and realizes active benign feedback and intelligent regulation of "voltage-sealing performance-voltage-sealing performance..."

[0079] The active control component interacts with the split-flap sealing unit through the mounting hole outside the sealing cavity. The active control component and the mounting hole are tightly matched through the sealing ring, which means that when the external electrical signal acts on the piezoelectric ceramic and the metal rod to produce displacement deformation, it will only move in the radial direction without displacement loss, and avoid the displacement offset phenomenon under multiple contact conditions. When the position of the elastic sealing component needs to be adjusted, different electrical signals can be applied to the piezoelectric ceramic as needed.

[0080] In a more preferred embodiment, the first magnetic member 71 is distributed all over the outer wall of the split-flap sealing unit 7, and the magnetism is equal everywhere, so that when an external effect occurs, the magnetic change of the second magnetic member 81 can act on the entire outer wall of the sealing unit 7, thereby achieving an overall response of the sealing deformation. The "distributed" in this solution can refer to the close array distribution of the first magnetic member or the distribution of the magnetic field.

[0081] In a more preferred embodiment, the wire for applying a control voltage to the piezoelectric crystal is connected to the piezoelectric ceramic 9 , and the wire for transmitting a feedback electrical signal is connected to the metal rod 8 .

[0082] In a more preferred embodiment, a signal interface is provided at the end of the small diameter section of the metal rod 8, and the signal interface is used to connect to a related test feedback system and a power supply system.

[0083] Embodiment 2:

[0084] An active foil gas film sealing structure based on electromagnetic induction. On the basis of Embodiment 1, as Figures 1 to 11 shown, a plurality of circumferentially distributed grooves 13 are formed in the inner wall of the sealing cavity 1, and the split sealing unit 7 is installed in the grooves 13; an axial slot 14 is formed between two adjacent grooves 13, and the axial slot 14 is used for installing an elastic sealing component.

[0085] The elastic sealing component includes a circumferential flat foil 5 and a split wave foil 6 located outside the circumferential flat foil 5; the circumferential flat foil 5 and the split wave foil 6 are in contact with each other.

[0086] The two ends of the split wave foil 6 in the circumferential direction are respectively a fixed end 61 and a separation boundary 63; the fixed end 61 is used for fixed installation on the sealing cavity 1; a plurality of separation gaps 62 are formed on the split wave foil 6 starting from the separation boundary 63, and the separation gaps 62 are perpendicular to the separation boundary 63.

[0087] The circumferential flat foil 5 is provided with an extension 51 extending in the outer diameter direction at one end close to the high-pressure side of the seal, and the extension 51 is clamped and fixed between the sealing cavity 1 and the pressing end cover 2.

[0088] An annular sealing groove 21 is provided on the inner side of the pressing end cover 2, a sealing gasket 23 is placed in the annular sealing groove 21, and the pressing end cover 2 and the sealing cavity 1 are connected by a set screw.

[0089] In this embodiment, the end where the split wave foil 6 is fixedly connected to the circumferential flat foil 5 is used as the fixed end, and the side far from the fixed end is used as the free end. A plurality of separation gaps 62 are formed on the split wave foil 6 on the side far from the fixed end. One end of the separation gap 62 extends to the separation boundary 63 at the free end and is perpendicular to the separation boundary 63 on this side, and the other end is closed.

[0090] An axial slot 14 is provided on the protruding part between two adjacent grooves 13 in the circumferential direction on the inner wall of the sealing cavity 1. The split wave foil 6 is placed in the axial slot 14 and an interference fit is adopted to ensure that the split wave foil 6 will not loosen or fall out of the axial slot 14.

[0091] In this embodiment, along the radial direction, the outer wall of the circumferential flat foil is in contact with the inner end of the split wave foil. The split wave foil is clamped between the circumferential flat foil and the split sealing unit, and Coulomb friction will occur between the split wave foil and the circumferential flat foil and the split sealing unit. Due to the load acting on the surface of the circumferential flat foil and the Coulomb friction between the circumferential flat foil and the split wave foil, the entire elastic sealing component can undergo small deformations in the radial direction and the circumferential direction, realizing real-time control and self-adaptive adjustment, so as to fully ensure the stability of the seal.

[0092] Preferably, the thickness of the integral circular flat foil is 0.25 - 0.35 mm.

[0093] Preferably, the thickness of the split wave foil is 0.25 - 0.35 mm.

[0094] Preferably, for the convenience of flanging the extension part 51, it can be set as a serrated structure.

[0095] Preferably, an annular sealing groove 21 is arranged inside the pressing end cover 2. A sealing gasket 23 is placed in the annular sealing groove 21. The set screw 200 passes through the through hole 22 to achieve the detachable connection between the end cover and the sealing ring. At the same time, by tightening the set screw 200, sufficient extrusion clamping of the extension part is achieved to ensure the effective fixation of the high-pressure end of the flat foil and prevent axial and radial movement; at the same time, the sealing gasket 23 is pressed tightly, which can also improve the sealing performance.

[0096] Preferably, a positioning groove 12 is also arranged at the end of the sealing cavity 1 for matching with the annular sealing groove 21 to jointly accommodate the sealing gasket 23.

[0097] In summary, this embodiment has at least the following functions:

[0098] (1) A unique piezoelectric crystal is designed to realize the adjustable change of the gap between the sealing system and the rotor. By adjusting the power supply signal of the piezoelectric crystal, it generates mechanical deformation with the change of voltage and frequency, and converts this deformation into a small displacement occurring in the radial direction, causing the split sealing unit to deform, further affecting the elastic sealing component and making it generate appropriate deformation. In this way, the active control operation of the sealing unit is realized, the sealing gap is adjustable, thereby significantly increasing the wedge space of the gas lubricating film, weakening the cross-coupling effect, enhancing the hydrodynamic effect, and ensuring that the sealing unit operates in the best working state.

[0099] (2) A solution is provided to solve the problems such as the passive control and poor self-regulation ability of the sealing unit in the prior art. Through a specially designed piezoelectric crystal, the "active" working mode and design method of the cylindrical gas film seal are realized. Through this transmission process of "electrical signal - mechanical deformation - force - displacement", the purpose of real-time optimization and regulation of the sealing performance is achieved, thereby preventing abnormal vibration impact and friction wear induced by uncertain excitation during the working process, and also avoiding the instability of the sealing system caused by sudden changes in the operating state, and greatly improving the anti-interference ability of the cylindrical gas film seal.

[0100] (3) It can convert extremely weak mechanical vibrations into electrical signals, so it can sensitively perceive subtle changes in the flow field. This enriches the monitoring methods of cylindrical sealing performance and realizes active benign feedback and intelligent control of "voltage-sealing performance-voltage-sealing performance..."

[0101] (4) By separating the petal-type corrugated foil circumferentially, with one end fixed and the other end free, the free end of the petal-type corrugated foil is prone to large deformation during actual operation. On the contrary, the deformation at the fixed end of the corrugated foil is small, which increases the circumferential wedge shape of the flow field. The secondary wedge effect brought about by this separation method can effectively enhance the buoyancy and provide better sealing performance.

[0102] (5) When facing high speed or variable working conditions, the elastic sealing component can make adaptive deformation, which can be transmitted to the active control component, causing it to change its position within a limited range, thereby affecting the flow field distribution. At the same time, the deformation ability of the elastic sealing component can also accommodate the radial offset or runout of the rotor component, compensating and balancing the inevitable processing errors and installation errors, significantly improving its applicability.

[0103] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

[0104] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In addition, the term "connected" used in this article can be directly connected or indirectly connected via other components without special explanation.

Claims

1. An active foil gas film seal structure based on electromagnetic induction, comprising a stator assembly and a rotor assembly. The stator assembly includes a sealing cavity (1) and a pressing end cover (2) detachably connected to one end of the sealing cavity (1). It is characterized in that, it further includes a plurality of split sealing units (7) evenly distributed along the circumferential direction on the inner wall side of the sealing cavity (1), and an elastic sealing assembly on the inner diameter side of the split sealing units (7); the rotor assembly is eccentrically installed on the radial inner side of the elastic sealing assembly. A plurality of dynamic pressure grooves (41) are provided on the rotor assembly and evenly distributed along the annular direction, and there is a gap between the rotor assembly and the elastic sealing assembly; it further includes a plurality of active control components. The active control components include a first magnetic member (71) located on the outer wall of the split sealing unit (7), a piezoelectric crystal located outside the split sealing unit (7), and a second magnetic member (81) located on the piezoelectric crystal. The first magnetic member (71) and the second magnetic member (81) are magnetically repulsive and have a gap.

2. The active foil gas film seal structure based on electromagnetic induction according to claim 1, characterized in that The piezoelectric crystal includes a metal rod (8) and a piezoelectric ceramic (9) coated outside the metal rod (8). The second magnetic member (81) is installed at the end of the metal rod (8).

3. The active foil gas film seal structure based on electromagnetic induction according to claim 2, wherein The metal rod (8) includes a large diameter section and a small diameter section, and the large diameter section and the small diameter section are coaxial; the piezoelectric ceramic (9) is coated outside the small diameter section, and the outer diameter of the piezoelectric ceramic (9) is equal to the outer diameter of the large diameter section; the second magnetic member (81) is installed at the end of the large diameter section away from the small diameter section.

4. The active foil air film sealing structure based on electromagnetic induction according to claim 2, characterized in that, A plurality of mounting holes (11) opposite to the first magnetic member (71) are provided on the sealing cavity (1) along the circumferential direction. The piezoelectric crystal is located in the mounting holes (11), and the hole wall of the mounting holes (11) is sealed with the metal rod (8) and / or the piezoelectric ceramic (9) through a sealing ring.

5. The active foil gas film seal structure based on electromagnetic induction according to claim 1, characterized in that A plurality of grooves (13) distributed along the circumferential direction are provided on the inner wall of the sealing cavity (1). The split sealing units (7) are installed in the grooves (13); an axial slot (14) is provided between two adjacent grooves (13), and the axial slot (14) is used to install the elastic sealing assembly.

6. The active foil gas film sealing structure based on electromagnetic induction according to claim 5, characterized in that The elastic sealing assembly includes an integral flat foil (5) and a split wave foil (6) located outside the integral flat foil (5); the integral flat foil (5) and the split wave foil (6) are in contact with each other.

7. The active foil gas film seal structure based on electromagnetic induction according to claim 6, characterized in that The two circumferential ends of the split wave foil (6) are respectively a fixed end (61) and a separation boundary (63); the fixed end (61) is fixedly installed on the sealing cavity (1) through the axial slot (14); a plurality of separation gaps (62) are provided on the split wave foil (6) starting from the separation boundary (63), and the separation gaps (62) are perpendicular to the separation boundary (63).

8. The active foil gas film sealing structure based on electromagnetic induction according to claim 6, characterized in that, The integral flat foil (5) is provided with an extension part (51) extending towards the outer diameter direction at one end close to the high-pressure side of the seal. The extension part (51) is clamped and fixed between the sealing cavity (1) and the pressing end cover (2).

9. The active foil gas film sealing structure based on electromagnetic induction according to claim 1, characterized in that The rotor assembly includes a rotating shaft (3) eccentrically passing through the sealing cavity (1), and a sleeve (4) fixedly sleeved outside the rotating shaft (3); a plurality of dynamic pressure grooves (41) are annularly and evenly distributed on the outer wall of the sleeve (4), and the dynamic pressure grooves (41) extend to the end face of the sleeve (4) facing the high-pressure side of the seal.

10. The active foil gas film sealing structure based on electromagnetic induction according to claim 1, wherein, An annular sealing groove (21) is arranged inside the pressing end cover (2), a sealing gasket (23) is placed in the annular sealing groove (21), and the pressing end cover (2) and the sealing cavity (1) are connected by set bolts.

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