Axial counterflow contact finger seal structure

Abstract

The application discloses an axial counterflow type contact fingertip sealing structure and belongs to the technical field of contact fingertip sealing of rotary machines. The structure comprises a front baffle, a fingertip sealing sheet laminated structure and a rear baffle which are coaxially arranged in sequence from a high-pressure side to a low-pressure side. The fingertip sealing sheet laminated structure comprises multiple layers of fingertip sealing sheets. The free end of the fingertip beam of each layer of fingertip sealing sheets is bent and extends towards the high-pressure side. A fingertip shoe is arranged at the free end of the fingertip beam and is in contact with the outer surface of a rotor for sealing. An annular pressure cavity is formed between the fingertip sealing sheet laminated structure and the front baffle. The sealing structure is simple and reliable in structure and good in adaptability. The integrated solution combining stiffness reset, back pressure enhancement and airflow assistance is adopted, so that stable, low-lag and high-efficiency contact sealing under dynamic working conditions is realized. The sealing structure is suitable for shaft end sealing of high-speed rotary machines such as aero-engines and gas turbines.

Description

Technical Field

[0001] This invention relates to a contact-type fingertip sealing structure for rotating machinery, and in particular to a novel fingertip sealing structure that utilizes the self-rigidity of the fingertip sealing sheet to reset and adopts an axial counterflow layout to improve dynamic sealing performance and reduce hysteresis. Background Technology

[0002] Finger seals, as a type of high-performance flexible dynamic seal, exhibit great application potential in advanced aero-engines and high-power-density rotating machinery due to their ability to allow for larger radial runout of the rotor and lower leakage than toothed seals. They represent an important development direction for next-generation high-performance dynamic sealing technology. Contact-type finger seals rely on the direct or indirect contact between the elastic metal fingertip sealing plate and the rotor surface to block leakage paths. Their basic working principle is: sealing is achieved through continuous or intermittent contact between the free end (finger shoe) of the fingertip sealing plate and the rotor surface, using this contact to prevent gas or liquid leakage, thereby achieving the sealing function.

[0003] However, traditional contact-type fingertip seals face two main challenges in practical applications: First, the hysteresis problem. When operating conditions change, especially when the speed decreases, the friction between the fingertip seal and the rotor causes wear of the fingertip seal and possible residual deformation, which prevents the fingertip seal from rebounding and resetting in a timely and complete manner, resulting in an increase in the instantaneous sealing gap and increased leakage, the so-called "hysteresis phenomenon". Second, the stability of the contact force. The contact force of the fingertip seal on the rotor mainly comes from its own bending preload. This force may change due to wear, thermal deformation and other factors during dynamic processes, affecting the long-term stability and uniformity of the seal.

[0004] To address the aforementioned issues, existing technologies propose the following solutions: 1. Introducing a spring element on the back of the fingertip seal to provide additional restoring force and improve hysteresis, but this increases structural complexity and axial dimensions; 2. Improving stress distribution and wear by optimizing the fingertip seal profile, but with limited improvement in hysteresis. In addition, there are some non-contact or hybrid fingertip seal solutions, which reduce wear, but have complex structures and require higher machining accuracy and operating conditions.

[0005] Therefore, proposing a novel contact-type fingertip seal structure that is relatively simple in structure, can effectively improve hysteresis, and can stably maintain contact force to meet the increasing demand for sealing performance in high-reliability rotating machinery has become an urgent problem to be solved. Summary of the Invention

[0006] In view of this, the present invention discloses an axial counterflow type contact fingertip seal structure to solve the shortcomings of existing contact fingertip seals in terms of hysteresis and contact force stability.

[0007] This invention provides an axial counter-flow contact-type fingertip seal structure for installation in the stationary casing of rotating machinery and mounted on the rotor 5. The axial counter-flow contact-type fingertip seal structure includes a front baffle 1, a stacked fingertip seal sheet structure, and a rear baffle 3 arranged coaxially from the high-pressure side to the low-pressure side. The high-pressure side of the front baffle 1 has an annular extension end 11 extending towards the rotor 5. The stacked fingertip seal sheet structure includes multiple layers of fingertip seal sheets 2. Each layer of fingertip seal sheet 2 includes a pressing end 21, a fingertip beam 22, and a fingertip shoe. 23; The pressing end 21 is annular and pressed and fixed between the front baffle 1 and the rear baffle 3; There are multiple fingertip beams 22 and they are evenly distributed along the circumference of the pressing end 21. The free end of each fingertip beam 22 is bent and extended towards the high pressure side to form a cantilever beam structure. There are multiple fingertip boots 23 and they are one by one set at the free end of the fingertip beam 22. The fingertip boots 23 are in contact with the outer surface of the rotor 5 to form an annular contact sealing strip. The fingertip sealing sheet stacked structure forms an annular pressure cavity 4 between the front baffle 2 and the fingertip sealing sheet stacked structure.

[0008] Preferably, the front baffle 1, the fingertip sealing sheet stack structure, and the rear baffle 3 are connected by axial fasteners.

[0009] Preferably, the fingertip sealing sheet 2 is made of spring steel or high-temperature alloy.

[0010] Further preferably, the sealing surface of the fingertip boot 23 of the fingertip sealing piece 2 is provided with a wear-resistant coating.

[0011] The axial counterflow contact fingertip seal structure provided by this invention is simple, reliable, and adaptable. Combined with an integrated solution of stiffness reset, back pressure enhancement, and airflow assistance, it achieves stable, low-hysteresis, and efficient contact sealing under dynamic operating conditions. It is suitable for shaft end sealing of high-speed rotating machinery such as aero engines and gas turbines. Attached Figure Description

[0012] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments:

[0013] Figure 1 A half-sectional schematic diagram of the axial counterflow contact fingertip seal structure provided by the present invention;

[0014] Figure 2 This is a schematic diagram of the structure of a fingertip sealing strip.

[0015] In the figure: 1-front baffle, 11-annular extension end, 2-finger tip sealing plate, 21-pressing end, 22-finger tip beam, 23-finger tip shoe, 3-rear baffle, 4-pressure chamber, 5-rotor. Detailed Implementation

[0016] To clarify the purpose, technical solution, and beneficial effects of this invention, the specific embodiments of the invention will be described in detail below with reference to the accompanying drawings. It should be noted that the same reference numerals in the drawings always represent the same or functionally equivalent components. The embodiments described in this invention are merely typical examples of this invention, intended to explain the technical features of this invention, and not to limit the scope of protection. Any equivalent substitutions or adaptive improvements derived by those skilled in the art based on the embodiments of this invention without inventive effort should be included within the scope of the claims of this invention.

[0017] like Figure 1 , Figure 2 As shown, this embodiment provides an axial counter-flow contact fingertip seal structure, installed in the stationary casing of rotating machinery and fitted onto the rotor 5. The axial counter-flow contact fingertip seal structure includes a front baffle 1, a stacked fingertip seal sheet structure, and a rear baffle 3, coaxially arranged from the high-pressure side to the low-pressure side. The high-pressure side of the front baffle 1 has an annular extension end 11 extending towards the rotor 5. The stacked fingertip seal sheet structure includes multiple layers of fingertip seal sheets 2; in this embodiment, there are four layers of fingertip seal sheets 2. Each layer of fingertip seal sheet 2 includes a pressing end 21. The rotor 5 comprises fingertip beams 22 and fingertip boots 23; the pressing end 21 is annular and pressed and fixed between the front baffle 1 and the rear baffle 3; there are multiple fingertip beams 22 evenly distributed along the circumference of the pressing end 21, and the free end of each fingertip beam 22 bends and extends towards the high pressure side to form a cantilever beam structure; there are multiple fingertip boots 23, each set at the free end of the fingertip beam 22; the fingertip boots 23 contact the outer surface of the rotor 5 to form an annular contact sealing strip; the fingertip sealing sheet stacked structure forms an annular pressure cavity 4 between the front baffle 2 and the fingertip sealing sheet stacked structure.

[0018] This axial counter-flow contact-type fingertip seal structure utilizes the bending stiffness of the fingertip seal itself. When the rotor experiences radial runout, it can elastically bend to avoid excessive wear or damage. After the runout ends, the fingertip seal can quickly rebound due to its elasticity, driving its free end to rapidly reset, improving sealing performance, dynamic response speed, and reducing hysteresis. By setting a pressure chamber, the high-pressure sealing medium (gas) can continuously enter this pressure chamber through the channel on the front baffle and act evenly on the back of the fingertip seal, generating pressure pointing towards the rotor and interacting with the fingertip seal. The elastic force of the fingertip seal enhances the stability and uniformity of the sealing contact, further improving the sealing hysteresis characteristics. The fingertip seal adopts an axial counter-flow layout (the bending direction of the fingertip seal is opposite to the axial direction of the mainstream leakage airflow). This utilizes the airflow to generate an airflow-assisted sealing effect (the leakage airflow acts on the fingertip shoe to generate aerodynamic force, and its radial component direction points towards the rotor center, which helps to press the fingertip seal against the rotor, forming an "airflow-assisted seal" and further enhancing the sealing contact force). It can also create a blocking effect on the leakage fluid, increase the flow resistance of the leakage, and form additional throttling and dissipation.

[0019] The working principle of this axial counterflow contact fingertip seal structure is as follows:

[0020] Under stable speed and pressure difference, the fingertip seal can maintain stable contact with the rotor surface and achieve a seal under the combined action of its own elastic force, back pressure component force and airflow auxiliary force.

[0021] If the rotor experiences eccentric whirling or radial runout, the fingertip shoe will be subjected to an upward impact force. At this time, the fingertip seal will undergo radial outward bending deformation due to its good elasticity, avoiding damage caused by hard collision and storing elastic potential energy. Meanwhile, the pressure distribution in the pressure chamber may undergo slight transient changes, but the overall back pressure support still exists.

[0022] When the rotor no longer experiences eccentric whirling or radial runout, the elastic potential energy stored in the deformed fingertip seal is rapidly released, generating a strong elastic restoring force that drives the fingertip shoe to rebound quickly downwards. At the same time, the back pressure of the pressure chamber always provides a downward radial component as a "backing" for the restoring force, ensuring that the rebound action is rapid and in place, allowing the fingertip seal to re-contact the rotor in a timely manner, greatly reducing the leakage window period caused by rebound delay (hysteresis).

[0023] If the rotor speed decreases, it may cause transient fluctuations in contact force due to centrifugal effect or changes in vibration state. At this time, the elastic force of the fingertip seal itself is still the main factor, while the back pressure of the pressure chamber, as a constant force source that does not depend on the speed, can effectively compensate for the possible contact force attenuation, maintain the stability of the sealing interface, and thus improve the sealing hysteresis characteristics during deceleration.

[0024] In summary, this invention provides a high-performance, high-reliability, and low-hysteresis contact fingertip sealing solution by integrating three major mechanisms: "stiffness reset", "back pressure enhancement" and "airflow assistance".

[0025] As an improvement to the technical solution, the front baffle 1, the fingertip sealing sheet stacked structure and the rear baffle 3 are connected by axial fasteners to restrict the axial movement of the fingertip sealing sheet stacked structure while allowing its radial elastic deformation.

[0026] As an improvement to the technical solution, the fingertip sealing sheet 2 is made of spring steel or high-temperature alloy.

[0027] As an improvement to the technical solution, the sealing surface of the fingertip boot 23 of the fingertip sealing sheet 2 is provided with a wear-resistant coating, which further ensures that the sealing structure has higher operational reliability and longer service life.

[0028] The specific embodiments of this invention adopt a progressive description principle, focusing on explaining the differentiated technical features between various embodiments. Common technical features can be cross-referenced by referring to corresponding embodiments. It should be clarified that the embodiments described in this invention are merely illustrative and not intended to limit the scope of protection of this invention. Based on the conventional knowledge of those skilled in the art, any equivalent substitutions or adaptive adjustments made to the structures, parameters, or processes described in the embodiments without departing from the core design concept of this invention should be considered to fall within the scope of protection defined by the claims of this invention.

[0029] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the implementation of the present invention is not limited to the specific embodiments described above. Any technical solution implemented within the framework of the present invention through logical equivalence, simple modification, or material substitution is within the scope of protection of the patent rights of the present invention.

Claims

1. An axial counter-flow type contact fingertip seal structure, used for installation in the stationary casing of rotating machinery and mounted on the rotor (5), characterized in that, The axial counter-flow contact fingertip seal structure includes a front baffle (1), a fingertip seal sheet stacked structure, and a rear baffle (3) arranged coaxially from the high-pressure side to the low-pressure side; the high-pressure side of the front baffle (1) is provided with an annular extension end (11) extending towards the rotor (5); the fingertip seal sheet stacked structure includes multiple layers of fingertip seal sheets (2); each layer of fingertip seal sheet (2) includes a pressing end (21), a fingertip beam (22), and a fingertip shoe (23); the pressing end (21) is annular and pressed and fixed to the front baffle. Between the plate (1) and the rear baffle (3); the fingertip beams (22) are multiple and evenly distributed along the circumference of the pressing end (21), and the free end of each fingertip beam (22) bends and extends towards the high pressure side to form a cantilever beam structure; the fingertip boots (23) are multiple and are set one by one at the free end of the fingertip beams (22); the fingertip boots (23) contact the outer surface of the rotor (5) to form a circular contact sealing strip; the fingertip sealing sheet stacked structure forms an annular pressure cavity (4) between the front baffle (2).

2. The axial counter-flow type contact fingertip seal structure according to claim 1, characterized in that, The front baffle (1), the fingertip sealing sheet stack structure and the rear baffle (3) are connected by axial fasteners.

3. The axial counter-flow type contact fingertip seal structure according to claim 1, characterized in that, The fingertip sealing sheet (2) is made of spring steel or high-temperature alloy.

4. The axial counter-flow type contact fingertip seal structure according to claim 1, characterized in that, The sealing surface of the fingertip boot (23) of the fingertip sealing piece (2) is provided with a wear-resistant coating.

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