A fluid static pressure gas film seal structure with metal skeleton for reversing between shafts

Abstract

The application belongs to the field of sealing structure design, and particularly relates to a metal-skeleton fluid static pressure gas film sealing structure for reverse shafts, which comprises an outer bushing, an outer rotor, an inner rotor and a sealing assembly. The outer rotor is arranged correspondingly to the inner rotor, the outer bushing is fixed on the outer rotor, and the inner rotor is fixed with a front runway and a rear runway. The sealing assembly is arranged between the front runway and the rear runway. The sealing assembly comprises an outer skeleton, a graphite sealing ring and an inner skeleton. The graphite open ring sealing is fixed and supported by the metal skeleton, which not only solves the problem that the thermal expansion amount of the floating ring sealing is relatively large under high temperature, and the large working gap leads to large leakage, but also reduces the contact force between the sealing ring and the outer bushing by bearing the centrifugal force of the graphite open ring under high-speed rotation, so that the sealing can generate static pressure gas film in the whole working condition range, and the problem that the sealing fails due to the fact that the gas film force cannot be balanced under the condition of high speed and low pressure is avoided.

Description

Technical Field

[0001] This application belongs to the field of sealing structure design, and specifically relates to a hydrostatic gas film sealing structure with a metal skeleton for use between reversing shafts. Background Technology

[0002] Due to the high relative rotational speed and high frictional linear velocity between the reversing shafts of gas turbines, grate seals are mostly used, resulting in significant gas leakage. To reduce leakage while avoiding the problems of high linear velocity and severe frictional wear, extensive research has been conducted on gas film seal structures using dynamic pressure, static pressure, or a combination of both. Commonly used structures include floating ring seals with dynamic or static pressure gas film structures and open ring seals with dynamic or static pressure gas film structures. Graphite materials are typically used to further reduce frictional wear.

[0003] Currently, there are two main types of contact seal structures for the reversing shaft of gas turbines: floating ring seals with dynamic or static pressure film structures and open ring seals. To reduce friction and wear, graphite and graphite carbon fiber materials are usually used.

[0004] For floating ring seals, because the coefficient of thermal expansion of graphite and carbon fiber materials is much lower than that of the metal material of the outer bushing, the gap between the floating ring and the outer bushing reaches more than 0.3mm under most operating temperatures, which greatly increases leakage and makes the performance unacceptable.

[0005] For open ring seals, the open ring rotates with the outer bushing during operation. The centrifugal force generated by the sealing ring under high-speed rotation is very large. The gas force is difficult to balance such a large centrifugal force. Under some working conditions, the sealing surface cannot generate an air film and abnormal friction and wear occur, causing the seal to fail quickly.

[0006] Therefore, how to improve the performance of the sealing structure is a problem that needs to be solved. Summary of the Invention

[0007] To address the aforementioned issues, this application provides a hydrostatic film seal structure with a metal skeleton for use between reversing shafts, thereby resolving the problems of leakage or wear in existing sealing structures.

[0008] The technical solution of this application is: a hydrostatic gas film sealing structure with a metal skeleton for reversing shafts, including an outer bushing, an outer rotor, an inner rotor and a sealing assembly;

[0009] The outer rotor and the inner rotor are arranged correspondingly, the outer bushing is fixed on the outer rotor, and the inner rotor is fixed with a front runway and a rear runway; a sealing assembly is provided between the front runway and the rear runway.

[0010] The sealing assembly includes an outer skeleton, a graphite sealing ring, and an inner skeleton; both the outer skeleton and the inner skeleton are metal structures, and the graphite sealing ring is disposed between the outer skeleton and the inner skeleton.

[0011] Preferably, the graphite sealing ring is an open ring structure, which can fit against the outer bushing after opening and can rotate synchronously with the outer bushing.

[0012] Preferably, when the graphite sealing ring reaches a stable state, the gas force F on the left side... 左 With the gas force F on the right 右 The frictional force F generated by the outer diameter f Once equilibrium is reached, the forces acting on the graphite sealing ring are as follows:

[0013] F 左 =F 右 +F f .

[0014] Preferably, the outer diameter friction of the graphite sealing ring is:

[0015] F f =f0·F 外 ;

[0016] Where f0 is the coefficient of friction, F 外 This is the contact force between the outer diameter of the sealing ring and the outer bushing.

[0017] Preferably, the outer ring friction of the graphite sealing ring is:

[0018] F 外 =F 离心 -F ｑ -F g ;

[0019] Where F 离心 For the centrifugal force of the sealing ring, F q F is the resultant force of the gas forces at the outer and inner diameters of the sealing ring; g The forces borne by the exoskeleton.

[0020] Preferably, the F 离心 for:

[0021] F 离心 =m·r·ω 2 ;

[0022] Where m is the weight of the graphite sealing ring, and r is the radius of the graphite sealing ring:

[0023] F = P·S;

[0024] Where F is the force on the inner or outer diameter of the graphite sealing ring, P is the pressure on the inner or outer diameter, and S is the area of ​​the inner or outer diameter of the graphite sealing ring.

[0025] The hydrostatic film seal structure with a metal skeleton for use between reversing shafts in this application has the following advantages:

[0026] The use of a metal skeleton to fix and support the graphite open ring seal solves the problem of large leakage caused by the large difference in thermal expansion of the floating ring seal at high temperature and the large working gap. The metal skeleton also bears the centrifugal force of the graphite open ring under high speed rotation, reducing the contact force between the sealing ring and the outer bushing. This allows the seal to generate a static pressure gas film in the entire operating range, avoiding the problem of seal failure caused by the unbalanced gas film force under high speed and low pressure conditions. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the overall structure of this application;

[0028] Figure 2 This is a schematic diagram of the sealing assembly structure of this application;

[0029] Figure 3 This is a schematic diagram of the working principle of the sealing assembly in this application;

[0030] Figure 4 This is a schematic diagram of the force balance of the sealing component in this application.

[0031] 1. Outer bushing; 2. Front runway; 3. Rear runway; 4. Inner rotor; 5. Sealing assembly; 6. Outer skeleton; 7. Graphite sealing ring; 8. Inner skeleton. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are only some, not all, of the embodiments of this application. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application. The embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0033] The first aspect of this application provides a hydrostatic film seal structure with a metal skeleton for use between reversing shafts, such as... Figures 1-2 It includes an outer bushing 1, an outer rotor, an inner rotor 4, and a sealing assembly 5;

[0034] The outer rotor and the inner rotor 4 are respectively arranged. The outer bushing 1 is fixed on the outer rotor. The front runway 2 and the rear runway 3 are fixed on the inner rotor 4. A sealing component 5 is provided between the front runway 2 and the rear runway 3.

[0035] The sealing assembly 5 has a cylindrical structure and includes an outer skeleton 6, a graphite sealing ring 7, and an inner skeleton 8. Both the outer skeleton 6 and the inner skeleton 8 are metal structures, and the graphite sealing ring 7 is located between the outer skeleton 6 and the inner skeleton 8.

[0036] The graphite sealing ring 7 is an open ring structure. When the graphite sealing ring 7 is opened, it can fit with the outer bushing 1 and rotate synchronously with the outer bushing 1 to bear the same load.

[0037] During operation, the high-pressure gas enters through the sealed left inlet and splits into three paths: such as... Figure 3 One path of gas flows out from the gap between the sealing assembly 5 and the outer bushing 1, as well as the opening gap of the sealing assembly 5, to the outlet; another path enters the balance tank through a certain number of gas film holes on the sealing assembly 5, where a portion of the gas flows radially outward along the gap between the sealing assembly 5 and the rear runway 3, merges with the first path of leaked gas, and flows to the outlet; the other portion of the gas flows radially inward along the gap between the sealing assembly 5 and the rear runway 3 into the inner cavity, and enters the outlet through the channel opened on the rear runway 3; and a third path flows into the inner cavity from the gap between the sealing assembly 5 and the front runway 2, merges with the second path of gas flowing radially inward, and enters the outlet through the channel opened on the rear runway 3.

[0038] The stress condition of sealing component 5 during operation is shown in the figure. Figure 4 When the sealing assembly 5 and the rear runway 3 are in contact, the pressure Pd of the gas entering the balance groove through the gas film hole is equal to the inlet pressure P0. Through the design of the balance groove area, the resultant force of the gas force on the right side is greater than the resultant force of the gas force on the left side and the frictional force of the sealing assembly 5 and the outer bushing 1. This causes the sealing assembly 5 to move to the left, and a gap appears between the sealing assembly 5 and the rear runway 3. Gas leaks radially upward and downward from the balance groove, and the pressure Pd in ​​the balance groove decreases until the resultant force on the left side and the resultant force on the right side reach equilibrium. There is a very small gap between the sealing assembly 5 and the front runway 2 and the rear runway 3, which generates a static pressure gas film. This avoids contact friction and wear between the sealing assembly 5 and the front runway 2 and the rear runway 3, thus ensuring that the seal can work under a very small gap for a long time.

[0039] In its initial state, the sealing ring 7 adheres to the outer bushing 1 by its own opening tension. During operation, as the sealing ring 7 rotates together with the outer bushing 2, the centrifugal force generated by the sealing ring 7 increases the adhesion force between the ring and the outer bushing 2. During this process, the outer frame 6 can tightly clamp the sealing ring 7, bearing most of the centrifugal force generated by the sealing ring 7, thereby reducing the adhesion force between the sealing ring 7 and the outer bushing 2, and thus making it easier for the sealing assembly 5 to achieve a state of force balance. The inner frame 8 serves to support the sealing ring 7 and can prevent the opening gap from closing under special working conditions such as transition states, where the gas force at the outer diameter of the sealing ring 7 is greater than the gas force at the inner diameter.

[0040] Preferably, the sealing structure design method is as follows:

[0041] When the graphite sealing ring reaches stability, the gas force F on the left side... 左 With the gas force F on the right 右 The frictional force F generated by the outer diameter f Once equilibrium is reached, the forces acting on the graphite sealing ring are as follows:

[0042] F 左 =F 右 +F f .

[0043] The outer diameter friction of the graphite sealing ring is:

[0044] F f =f0·F 外 ;

[0045] Where f0 is the coefficient of friction, F 外 This is the contact force between the outer diameter of the sealing ring and the outer bushing.

[0046] The outer ring friction of the graphite sealing ring is:

[0047] F 外 =F 离心 -F ｑ -F g ;

[0048] Where F 离心 For the centrifugal force of the sealing ring, F q F is the resultant force of the gas forces at the outer and inner diameters of the sealing ring; g The forces borne by the exoskeleton.

[0049] In the design, the centrifugal force F 离心 The sum of the centrifugal forces of the outer frame and the sealing ring can also be calculated using simulation analysis methods. F 离心 for:

[0050] F 离心 =m·r·ω 2 ;

[0051] Where m is the weight of the graphite sealing ring and r is the radius of the graphite sealing ring.

[0052] Gas force F q Calculate the forces acting on the inner and outer diameters separately, and then calculate the resultant force. The formulas for calculating the forces acting on the inner and outer diameters are as follows:

[0053] F = P·S;

[0054] Where F is the force on the inner or outer diameter of the graphite sealing ring, P is the pressure on the inner or outer diameter, and S is the area of ​​the inner or outer diameter of the graphite sealing ring.

[0055] Contact force F between the outer diameter of the sealing ring and the outer bushing 外 The forces that need to be controlled, including centrifugal force and gas force, are related to the structural design; therefore, the force F borne by the outer frame is... g The force is controlled through structural design, and the working state of the exoskeleton under force F can be analyzed using simulation methods. g Calculate the diameter of the sealing ring in its free state. The outer skeleton operates under a force F. g The diameter of the sealing ring should be such that its outer diameter is equal to the inner diameter of the outer bushing.

[0056] Considering the difficulty in ensuring the machining accuracy of the sealing ring and outer frame diameters in engineering design, as well as meeting the contact force requirements under different working conditions, it is advisable to maintain a very small gap between the outer diameter of the sealing ring and the inner diameter of the outer bushing under all working conditions to meet the sealing requirements. Under this condition, the outer frame is subjected to a force F. g Then with centrifugal force F 离心 equal.

[0057] The opening gap of the sealing ring should be kept small under all conditions, and can be designed to have a zero gap under extreme conditions.

[0058] In summary, this application has the following advantages:

[0059] The use of a metal skeleton to fix and support the graphite open ring seal solves the problem of large leakage caused by the large difference in thermal expansion of the floating ring seal at high temperature and the large working gap. The metal skeleton also bears the centrifugal force of the graphite open ring under high speed rotation, reducing the contact force between the sealing ring and the outer bushing. This allows the seal to generate a static pressure gas film in the entire operating range, avoiding the problem of seal failure caused by the unbalanced gas film force under high speed and low pressure conditions.

[0060] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A hydrostatic film seal structure with a metal skeleton for use between reversing shafts, characterized in that, It includes an outer bushing (1), an outer rotor, an inner rotor (4), and a sealing assembly (5); The outer rotor and the inner rotor (4) are respectively arranged, the outer bushing (1) is fixed on the outer rotor, and the inner rotor (4) is fixed with a front runway (2) and a rear runway (3); a sealing assembly (5) is provided between the front runway (2) and the rear runway (3); The sealing assembly (5) includes an outer skeleton (6), a graphite sealing ring (7), and an inner skeleton (8); both the outer skeleton (6) and the inner skeleton (8) are metal structures, and the graphite sealing ring (7) is disposed between the outer skeleton (6) and the inner skeleton (8); The graphite sealing ring (7) is an open ring structure. When the graphite sealing ring (7) is opened, it can fit with the outer bushing (1) and can rotate synchronously with the outer bushing (1).

2. The hydrostatic film seal structure with a metal skeleton for use between reversing shafts as described in claim 1, characterized in that, When the graphite sealing ring reaches a stable state, the gas force F on the left side... 左 With the gas force F on the right 右 The frictional force F generated by the outer diameter f Once equilibrium is reached, the forces acting on the graphite sealing ring are as follows: F 左 =F 右 +F f 。 3. The hydrostatic film seal structure with a metal skeleton for use between reversing shafts as described in claim 2, characterized in that, The outer diameter friction of the graphite sealing ring is: F f =f0·F 外 ; Where f0 is the coefficient of friction, F 外 This is the contact force between the outer diameter of the sealing ring and the outer bushing.

4. The hydrostatic film seal structure with a metal skeleton for use between reversing shafts as described in claim 2, characterized in that, The outer ring friction of the graphite sealing ring is: F 外 =F 离心 -F ｑ -F g ; Where F 离心 For the centrifugal force of the sealing ring, F q F is the resultant force of the gas forces at the outer and inner diameters of the sealing ring; g The forces borne by the exoskeleton.

5. The hydrostatic film seal structure with a metal skeleton for use between reversing shafts as described in claim 4, characterized in that, The F 离心 for: F 离心 =m·r·ω 2 ; Where m is the weight of the graphite sealing ring and r is the radius of the graphite sealing ring; F q Calculate the forces acting on the inner and outer diameters separately, and then calculate the resultant force. The formulas for calculating the forces acting on the inner and outer diameters are as follows: F = P·S; Where F is the force on the inner or outer diameter of the graphite sealing ring, P is the pressure on the inner or outer diameter, and S is the area of ​​the inner or outer diameter of the graphite sealing ring.

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