Follow-up clearance self-adjusting comb tooth steam seal

Abstract

A follow-up clearance self-adjusting comb tooth steam seal comprises a rotor shaft provided with a steam seal boss and a steam seal block forming a steam seal ring body, copper alloy long steam seal teeth matched with the shaft face of the rotor shaft are embedded in the inner diameter face of the steam seal block, and a groove-shaped section assembling groove with a notch facing the steam facing side is formed in the position, located between every two adjacent long steam seal teeth, of the steam seal block. A row of bimetallic strip short steam sealing teeth matched with a rotor shaft steam sealing boss is assembled through the assembling groove, each short steam sealing tooth is composed of an embedding part matched with the assembling groove and a steam sealing tooth part which is in transition connection through an arc and inclines towards the steam facing side by an angle alpha, and the short steam sealing teeth are connected with the two ends of the embedding part of the assembling groove in an end-to-end mode. The steam sealing tooth parts of every two adjacent short steam sealing teeth are partially overlapped, and positioning protection teeth matched with the short steam sealing teeth are arranged on the inner diameter face of the steam sealing block. The self-adjustment of the radial clearance of the steam seal teeth can be realized, steam seal rub-impact during starting and stopping is avoided, and meanwhile, a smaller steam seal working radial clearance is realized, so that the efficiency and the safety are improved.

Description

Technical Field

[0001] The utility model relates to a steam turbine seal, in particular to a comb-teeth steam seal with a follower clearance and self-adjustment. Background Art

[0002] Comb-tooth steam seals are widely used in large, medium, and small steam turbines due to their low cost, simple structure, safety, reliability, and ease of installation. These seals typically feature multiple seal bosses on the rotor shaft, forming a seal ring composed of six to eight seal blocks. Long seal teeth, which mate with the rotor shaft surface, and short seal teeth, which mate with the seal bosses on the rotor shaft, are spaced apart on the inner diameter surface of the seal blocks. This creates a tortuous sealing channel, achieving multi-stage throttling to reduce axial steam leakage. A major problem with comb-tooth steam seals is the wear of the seal teeth. This is particularly true during turbine startup and shutdown, when the rotor excursion amplitude is large. This requires a small radial clearance to improve sealing performance while also preventing friction between the seal teeth and the rotor shaft, presenting a challenging design challenge. Traditional comb-tooth steam seals can only achieve this by increasing the radial clearance, sacrificing economic efficiency to ensure unit safety. Existing self-adjusting steam seals employ a spring mounted at the end of the seal block and a steam channel extending directly to the back arc of the seal block. The spring and steam pressure adjust the radial clearance between the seal teeth and the rotor shaft. This addresses the seal rubbing problem associated with conventional comb-tooth seals, which can occur during startup and shutdown due to excessive rotor vibration during critical periods. However, these self-adjusting seals place high demands on steam quality, seal processing dimensions, and installation techniques, making the seal block prone to failure to fully close. Consequently, their reliability remains unsatisfactory. Utility Model Content

[0003] The purpose of the utility model is to provide a comb-tooth steam seal with a self-adjusting follower clearance, which has good adaptability and reliability, is easy to process and install, can effectively solve the steam seal friction problem existing in the comb-tooth steam seal, ensure the sealing effect, and thus improve the efficiency and safety of the steam turbine unit.

[0004] The technical solution for achieving the above-mentioned purpose is as follows: a self-adjusting comb-tooth steam seal with a follower clearance comprises a rotor shaft provided with a plurality of steam seal bosses and a steam seal block constituting a steam seal ring body, wherein long copper alloy steam seal teeth that match the axial surface of the rotor shaft are embedded at regular intervals on the inner diameter surface of the steam seal block, and a groove-shaped cross-section assembly groove with a notch facing the steam-facing side is provided on the steam seal block between two adjacent long steam seal teeth, and a row of short bimetallic steam seals that match the steam seal bosses of the rotor shaft are assembled through the assembly groove. Tooth, the short steam seal tooth is composed of a fitting part that cooperates with the assembly groove and a steam seal tooth part that is connected through an arc transition and inclined to the steam-facing side at an angle of α. The short steam seal tooth is connected end to end with both ends of the fitting part of the assembly groove. The tail end of the steam seal tooth part of the short steam seal tooth is extended backward for a section and the extended section partially overlaps with the steam seal tooth part of the next short steam seal tooth. A positioning guard tooth that cooperates with the short steam seal tooth is provided on the inner diameter surface of the steam seal block, located on the back-steam side of the short steam seal tooth.

[0005] The above-mentioned follower gap self-adjusting comb teeth steam seal has an L-shaped cross-section embedding groove on the steam seal block to embed the long steam seal teeth.

[0006] The above-mentioned follower clearance self-adjusting comb teeth steam seal has an α angle of 5°-15°.

[0007] The short steam seal teeth of this follower clearance self-adjusting comb-tooth steam seal adopt a bimetallic structure and are tilted at an angle α toward the steam-facing side. At low temperatures, a relatively large radial gap is formed between the short steam seal teeth and the steam seal boss of the rotor shaft. As the temperature rises, the deformation caused by the difference in thermal expansion coefficients of different metals in the bimetallic strip causes the steam seal tooth part of the short steam seal teeth to gradually become perpendicular to the rotor shaft, thereby reducing the radial sealing gap between the steam seal teeth and the rotating shaft. This greatly improves the sealing performance of the steam seal while avoiding excessive vibration of the rotor when it passes critical during the start-up and shutdown of the unit, which may cause steam seal collision.

[0008] The short steam seal teeth of the self-adjusting comb-teeth steam seal with follower clearance adopt a multi-unit arrangement structure, which is conducive to the retreat of the short steam seal teeth when they collide with the rotating shaft, and can also realize partial replacement of the short steam seal teeth.

[0009] The short seal teeth of the comb-tooth seal with self-adjusting follower clearance are tilted toward the steam-facing side at an angle α. Under the action of the bimetallic structure, as the temperature rises, the angle α gradually decreases until it reaches zero, thereby compensating for the axial expansion difference of the rotor and solving the problem of seal teeth "falling off".

[0010] The long steam seal teeth of this follow-up clearance self-adjusting comb-tooth steam seal adopt copper alloy steam seal teeth with a relatively large expansion coefficient, which realizes self-adjustment of the radial clearance between the long steam seal teeth and the rotor shaft. It is also beneficial to avoid steam seal collision during the start-up and shutdown of the steam turbine unit, and maintain a smaller radial clearance of the steam seal after entering the working state.

[0011] The utility model is convenient to process and install, has high reliability, and can effectively improve the efficiency and safety of the steam turbine unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Attachment Figure 1 This is a structural diagram of the self-adjusting comb-teeth steam seal with follower clearance.

[0013] Attachment Figure 2 It is a three-dimensional structural diagram of the comb-teeth steam seal with self-adjusting follower clearance.

[0014] Attachment Figure 3 This is a schematic diagram of the short steam seal tooth structure of the follower clearance self-adjusting comb teeth steam seal.

[0015] In the figure: 1. Rotor shaft; 2. Steam seal block; 3. Long steam seal tooth; 4. Assembly groove; 5. Short steam seal tooth; 51. Inner active layer; 52. Outer passive layer; 6. Positioning protection tooth. DETAILED DESCRIPTION

[0016] The present invention will be described in further detail below with reference to the accompanying drawings.

[0017] like Figure 1 、 Figure 2This self-adjusting comb-tooth steam seal with a follower clearance includes a rotor shaft 1 equipped with multiple steam seal bosses and a steam seal block 2 that forms a steam seal ring. In the embodiment shown in the accompanying drawings, the rotor shaft 1 is provided with three steam seal bosses with a rectangular cross-section. The steam seal block 2 is an arc-shaped steam seal block with an I-section, machined from heat-resistant steel and arranged end-to-end. Long copper alloy steam seal teeth 3, which mate with the axial surface of the rotor shaft 1, are embedded at regular intervals on the inner diameter surface of the steam seal block 2. In the embodiment shown in the accompanying drawings, L-shaped grooves are provided on the steam seal block 2 to allow for clearance fit of the long steam seal teeth 3. The long steam seal teeth 3 are machined from tin bronze, brass, or molybdenum copper. A groove-shaped cross-section assembly groove 4 with a notch facing the steam-facing side is provided between two adjacent long steam-seal teeth 3 on the steam-seal block 2. The assembly groove 4 has a groove cavity outlet located on the inner diameter surface of the steam-seal block 2. A row of short bimetallic steam-seal teeth 5 that cooperate with the steam-seal boss of the rotor shaft 1 are assembled through the assembly groove 4. The short steam-seal teeth 5 are composed of a fitting portion that cooperates with the assembly groove 4 and a steam-seal tooth portion that is connected by an arc transition and inclined at an angle α toward the steam-facing side. The angle α is 5°-15° and is selected within the range of 5°-15° based on the steam-seal operating temperature. A relatively large α angle corresponds to a relatively high steam-seal operating temperature. The short steam-seal teeth 5 are connected end to end with the fitting portion of the assembly groove 4. The tail end of the steam-seal tooth portion of the short steam-seal tooth 5 extends rearward for a section, and this extension partially overlaps with the steam-seal tooth portion of the subsequent short steam-seal tooth 5. After the short steam seal teeth 5 are fitted into the assembly grooves 4, a clearance space is left between the outer arc surface of the arc transition section and the assembly grooves 4. Positioning guard teeth 6 are provided on the inner diameter surface of the steam seal block 2, on the back-to-steam side of the short steam seal teeth 5, to cooperate with the short steam seal teeth 5. The positioning guard teeth 6 consist of a radial tooth portion perpendicular to the rotor shaft 1 and an arc transition section connected to the steam seal block 2 and cooperating with the inner arc surface of the transition arc of the short steam seal teeth 5.

[0018] like Figure 3 The short seal teeth 5 of this self-adjusting comb-tooth steam seal with follower clearance are bimetallic structures comprising an inner active layer 51 and an outer passive layer 52. The outer passive layer 52 constitutes the main structure of the short seal teeth 5. The inner active layer 51 is composed of arc segments and straight tooth segments and is attached to the inner side of the outer passive layer 52 by vacuum brazing or high-temperature hot pressing. The straight tooth segments of the inner active layer 51 are shorter than those of the outer passive layer 52, with a difference of 2mm-3mm. The outer passive layer 52 is made of nickel alloy steel, such as GH4145 or GH4169. The inner active layer 51 is made of manganese-nickel-copper alloy or molybdenum-copper.

Claims

1. A comb-teeth steam seal with a self-adjusting follower clearance, comprising a rotor shaft (1) provided with a plurality of steam seal bosses and a steam seal block (2) constituting a steam seal ring body, wherein: The inner diameter surface of the steam seal block (2) is embedded with copper alloy long steam seal teeth (3) that match the axial surface of the rotor shaft (1) at a certain interval. A groove-shaped cross-section assembly groove (4) with a notch facing the steam-facing side is provided between two adjacent long steam seal teeth (3) on the steam seal block (2). A row of bimetallic short steam seal teeth (5) that match the steam seal boss of the rotor shaft (1) are assembled through the assembly groove (4). The short steam seal teeth (5) are formed by an engaging portion that matches the assembly groove (4). The short steam seal tooth (5) is connected with the two ends of the fitting part of the assembly groove (4) by an arc transition and is inclined at an angle α toward the steam-facing side. The tail end of the steam seal tooth part of the short steam seal tooth (5) is extended backward for a section and the extended section partially overlaps with the steam seal tooth part of the next short steam seal tooth (5). A positioning guard tooth (6) cooperating with the short steam seal tooth (5) is provided on the inner diameter surface of the steam seal block (2) at the back-steam side of the short steam seal tooth (5).

2. The self-adjusting comb seal with follower clearance according to claim 1 is characterized in that: The steam seal block (2) is provided with an L-shaped cross-section embedding groove for embedding the long steam seal teeth (3).

3. The comb-teeth steam seal with self-adjusting follower clearance according to claim 1 is characterized in that: The angle α is 5°-15°.

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