Steam turbine moving vane shroud structure

Abstract

The invention relates to a shroud band structure of movable blade of turbine. Wherein, the whole level of movable blade is mounted on the wheel groove of rotor whose shroud bands are matched along circumference; the radial surface of nearby shroud bands have assemble space. The invention is characterized in that: the radial match surface of shroud band is arranged with one axial groove whose section is in V shape; the groove is mounted with damper; when the blade rotates in high speed and deforms, the radial surface is contacted to the damper all the time, to generate mechanical damp on the nearby two blades, to confirm the structural rigidity of blade, and reduce the movable stress, to improve the safety. The top of shroud band is step structure, mounted with axial steam left groove, in which the leaked airflow will form vortex, to increase the resistance on the leaked airflow.

Description

technical field [0001] The present invention relates to steam turbine moving blades, especially its shroud structure. Background technique [0002] The technical development of steam turbines for power generation is carried out with the goal of increasing the capacity of a single unit and improving the steam pressure, thermal efficiency and reliability of the unit. The increase of unit capacity and the increase of steam pressure will inevitably greatly increase the load and pressure of blades at all levels. For example, the load of a 600MW steam turbine's high and medium pressure blade stage is 2.5 times that of a 300MW steam turbine, and the pressure it bears is about 1.5 times. The exciting force and the bending stress borne in the working state are significantly increased, which brings safety problems. To solve this technical problem, the moving blades of large steam turbines are designed with shrouds, and the structure of the shrouds is mostly in the form of an integral ...

AI Technical Summary

Problems solved by technology

Refer to Figure 1 and Figure 2 for the existing overall shroud structure. Since the blades will be twisted and deformed when the unit is running, the overall shroud is designed as a pre-twisted type, that is, the shrouds of adjacent blades are designed to match the A and B surfaces. The pre-twisted amount D, the structure has the following two defects: 1. The torsional recovery X angle of the high-load moving blade of a large steam turbine is small, usually between 10' and 1°, and the pre-twisted amount D (blade torsional recovery The size of the largest X angle) is only 0.4--0.8mm. Therefore, the processing and assembly of the blade are very difficult, and it is difficult to achieve the accuracy required by the design. This leads to the inconsistency between the pre-twisted amount D and the actual twisted amount of the blade, that is In the case of transitional pre-twisting or pre-twisting is not in place, the shrouds of adjacent blades do not coincide well with the radial mating surfaces, and the structural rigidity and safety of the blades cannot be guaranteed

2. When the blade is assembled, the blade root must rotate. In order to prevent the blade root from rotating, a fixed surface must be set on the blade root (different blade root structures have different fixed surfaces), which makes the structure of the blade root complicated, and the fixed surface The processing accuracy is high (generally 0.01--0.025mm), but it is difficult to guarantee the actual processing, and the fixing surface is not well matched, which causes a large residual stress to the blade root, thus affecting the safety of the blade

[0003] In addition, with the increase of steam pressure, the loss of steam leakage between dynamic and static gaps increases significantly, reducing the efficiency and economy of the unit

Referring to Figure 3, in order to reduce the loss of steam leakage, the top of the existing shroud is designed as a high-low step structure, and the height difference is generally 3.8mm. Correspondingly, the seal teeth on the stator matched with the shroud are also designed as high-low teeth , which makes the steam leakage channel tortuous, increases the resistance to the steam leakage flow, and reduces the leakage volume to a certain extent. However, the steam leakage is still relatively large, and the structure of the steam seal needs to be further improved.

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