Axial flow compression type positioning impeller shaft system structure for steam turbine

Abstract

The invention discloses an axial flow compression type positioning impeller shaft system structure for a steam turbine, the impeller shaft system structure comprises a shaft body, an impeller and a force application jacking assembly, the impeller is clamped on the shaft body, and the force application jacking assembly is located on the rear side of the impeller and used for compressing and fixing the impeller and the shaft body. The rotating shaft has the advantages of being large in adaptive temperature range and easy to assemble and disassemble.

Description

Technical Field

[0001] The invention relates to the field of steam turbine rotors, in particular to an axial flow compression type positioning impeller shaft system structure for steam turbines. Background Art

[0002] The working conditions of steam turbines are relatively harsh, and they are required to maintain extremely high precision. For example, our shaft system works in an environment with extreme changes in temperature, and sometimes the temperature difference between the cold and hot states is as high as 300℃ to 400℃. At this time, due to the difference in thermal properties of the various components of the shaft system (mainly manifested in the difference in thermal expansion coefficient), the shaft system structure may become loose during the change in temperature; at the same time, the shaft system rotates at high speed, which has high requirements for dynamic balance.

[0003] Therefore, it is necessary to design an axial flow compression positioning impeller shaft system structure for steam turbines with a wide temperature range. Summary of the invention

[0004] The technical problem to be solved by the present invention is that due to the difference in thermal properties of various components of the shaft system (mainly manifested in the difference in thermal expansion coefficient), the shaft system structure may become loose during hot and cold changes; at the same time, the shaft system rotates at high speed and has high requirements for dynamic balance.

[0005] In order to solve the above technical problems, a technical solution adopted by the present invention is to provide an axial flow compression type positioning impeller shaft system structure for a steam turbine,

[0006] The shaft body is provided with a wedge-shaped shoulder, one end of the impeller is provided with a concave wedge-shaped force-applying surface A, and the other end of the impeller is provided with a convex wedge-shaped force-applying surface, and the concave wedge-shaped force-applying surface A of the impeller matches the wedge-shaped shoulder.

[0007] The force-applying and tightening assembly includes a tightening bolt, a pair of shaft stop half rings, a cover, a threaded top ring and a pressure cover. The surface of the shaft body is arranged with an annular groove. The pair of shaft stop half rings are connected into a whole by bolts. The pair of shaft stop half rings are both embedded in the annular groove. A recessed wedge-shaped force-applying surface B is provided on the inner side of the pressure cover. The recessed wedge-shaped force-applying surface B of the pressure cover cooperates with the convex wedge-shaped force-applying surface of the impeller.

[0008] In addition, the present invention also involves complex mechanisms such as top force and structure, material and thermal changes. It is required to apply a reasonable top force to limit the structure to produce a large elastic deformation; when the thermal expansion coefficient of the impeller hub and other materials is required to be greater than or equal to the thermal expansion coefficient of the shaft body material, a better effect can be obtained.

[0009] The beneficial effects of the present invention are as follows:

[0010] By providing a wedge-shaped shoulder and a wedge connection between the impeller and the shaft body, the axial pressing force is converted into a radial clamping force, eliminating the radial clearance between the shaft and the impeller and maintaining the dynamic balance state of the rotor.

[0011] By applying an appropriate axial pre-tightening force in the assembly structure, even in high-temperature and ultra-high-speed applications, the tight fit between the shaft and shaft accessories can be maintained, preventing the dynamic balance of the rotor from being damaged under harsh operating conditions and enabling the machine to operate stably.

[0012] The impeller has a reasonable clearance from the shaft diameter in the cold state and under non-loaded axial force, facilitating assembly. When the impeller is subjected to axial forces of different magnitudes in the cold state, the inner diameter undergoes slight changes, forcing the impeller to fit closely with the shaft and ensuring a tight fit in the cold state. On this basis, an additional pre-tightening force is applied to cause elastic deformation of the impeller on the shaft. This deformation resistance is sufficient to compensate for the tendency to generate gaps at high temperatures, thus perfectly solving the problem of unstable operation of high-speed heat engines. Better results can be obtained if the thermal expansion coefficient of the impeller material is greater than (or equal to) that of the shaft body. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic three-dimensional structure diagram of the shafting assembly of the present invention;

[0014] Figure 2 It is a schematic right-view structure diagram of the shafting of the present invention;

[0015] Figure 3 It is a schematic cross-sectional structure diagram of the shafting of the present invention taken along A-A;

[0016] Figure 4 It is a schematic front-view structure diagram of the impeller of the present invention;

[0017] Figure 5 It is a schematic cross-sectional structure diagram of the impeller of the present invention taken along B-B;

[0018] Figure 6 It is a schematic three-dimensional structure diagram of the impeller of the present invention;

[0019] Figure 7 It is a schematic three-dimensional structure diagram of the shaft body of the present invention;

[0020] Figure 8 It is a schematic three-dimensional structure diagram of the gland of the present invention;

[0021] Figure 9 It is a schematic three-dimensional structure diagram of the threaded top ring of the present invention;

[0022] Figure 10 It is a schematic front-view structure diagram of the threaded top ring of the present invention.

[0023] In the figure: 1, shaft body; 2, impeller; 3, wedge-shaped shaft shoulder; 4, concave wedge-shaped force application surface A; 5, convex wedge-shaped force application surface; 6, tightening bolt; 7, shaft retaining half-ring; 8, cover; 9, threaded top ring; 10, gland; 11, annular groove; 12, concave wedge-shaped force application surface B; 13, top hole; 14, threaded hole; 15, elastic gain notch. Detailed implementation manner

[0024] The following elaborates on the preferred embodiments of the present invention in conjunction with the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making the protection scope of the present invention more clearly defined.

[0025] Regarding the composition of the shafting: Please refer to Figure 1-10 , the impeller shaft includes a shaft body 1, an impeller 2 and a force application and tightening assembly. The impeller 2 is clamped on the shaft body 1, and the force application and tightening assembly is located at the rear side of the impeller 2 and is used to press and fix the impeller 2 to the shaft body 1.

[0026] Regarding the shaft body: A wedge-shaped shaft shoulder 3 is provided on the shaft body 1. One end of the impeller 2 is provided with a concave wedge-shaped force application surface A4, and the other end of the impeller 2 is provided with a convex wedge-shaped force application surface 5. The concave wedge-shaped force application surface A4 of the impeller 2 cooperates with the wedge-shaped shaft shoulder 3.

[0027] Regarding the force application and tightening assembly: The force application and tightening assembly includes a tightening bolt 6, two shaft retaining half-rings 7, a cover 8, a threaded top ring 9 and a gland 10. An annular groove 11 is arranged on the surface of the shaft body 1. The two shaft retaining half-rings 7 are connected into a whole by bolts. The two shaft retaining half-rings 7 are both clamped in the annular groove 11. The inner side of the gland 10 is provided with a concave wedge-shaped force application surface B12. The concave wedge-shaped force application surface B12 of the gland 10 cooperates with the convex wedge-shaped force application surface 5 of the impeller 2. Semi-annular grooves are opened on the opposite sides of the threaded top ring 9 and the cover 8. The shaft retaining half-rings 7 are located in the semi-annular grooves. The threaded top ring 9 and the cover 8 are fixed by bolts. A through hole is opened on the cover 8. The threaded top ring 9 is located on the other side of the gland 10. A top hole 13 is opened on the opposite sides of the gland 10 and the threaded top ring 9. A threaded hole 14 is penetrated through the threaded top ring 9. The top hole 13, the threaded hole 14 and the through hole are opposite. The tightening bolt 6 is inserted into the through hole; the wedge-shaped connection between the impeller 2 and the shaft body 1 converts the axial pressing force into a radial clamping force, eliminating the radial clearance between the shaft and the impeller 2 and maintaining the dynamic balance state of the rotor.

[0028] Regarding the impeller: A number of equally spaced elastic notches 15 are opened on the convex wedge-shaped force application surface 5 of the impeller 2. This structure makes the concave wedge-shaped force application surface A4 rigid, while the convex wedge-shaped force application surface 5 has elasticity. The so-called elasticity means that the convex wedge-shaped force application surface 5 has a certain elastic compressibility.

[0029] Regarding the characteristics and parameters of the wedge-shaped structure: The wedge-shaped shaft shoulder 3 adopts an inclined wedge angle structure. The left end of the first-stage shaft-mounted accessory can ensure reliable coaxial positioning; the right end also has a pressing and positioning effect on the next-stage impeller 2, enabling the first-stage accessory to ensure a high degree of coaxial accuracy; and a number of impellers 2 are successively connected in series to maintain reliable fitting coaxiality (compared with ordinary shaft structures, which all have gaps). A threaded top ring 9 with the same structure is also arranged at the rear end of the last-stage impeller 2, thereby obtaining high precision and stability of the overall structure. Generally, it is appropriate to take the inclination angle between 7° and 5° to achieve better results.

[0030] Regarding the magnitude of the applied force: The impeller has a reasonable gap with the shaft diameter under cold conditions and without an applied axial force, facilitating assembly; under cold conditions, when the impeller is subjected to axial forces of different magnitudes, the inner diameter will undergo slight changes, forcing the impeller to fit fully with the shaft to ensure fitting under cold conditions; on this basis, an additional pre-tightening force is applied to cause sufficient elastic deformation of the impeller on the shaft. This part of the deformation resistance is sufficient to compensate for the tendency to generate gaps at high temperatures, thus perfectly solving the problem of unstable operation of high-speed heat engines.

[0031] Assembly method of the axial compression type positioning impeller shaft system structure for a steam turbine in this solution:

[0032] Case A: Installation of a single impeller

[0033] First, install the impeller 2 on the shaft body 1 so that the wedge-shaped shaft shoulder 3 mates with the recessed wedge-shaped force application surface A4 of the impeller. Then, install the gland 10 on the shaft body 1 so that the recessed wedge-shaped force application surface B12 mates with the protruding wedge-shaped force application surface 5 of the impeller 2. Then, install the jacking device, and finally measure and adjust the jacking force of the jacking bolt 6.

[0034] Case B: Installation of multiple impellers

[0035] It is basically the same as Case A. The difference is that after installing the first-stage impeller, the second-stage impeller, the third-stage impeller, etc. are successively installed, and finally the last-stage impeller is installed; then the subsequent steps are the same as above.

[0036] The above are only embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the description and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall be similarly included in the patent protection scope of the present invention.

Claims

1. An axial-flow compression type positioning impeller shafting structure for a steam turbine, characterized in that: The impeller shafting structure includes a shaft body (1), an impeller (2), and a force-applying and tightening assembly. The impeller (2) is clamped on the shaft body (1), and the force-applying and tightening assembly is located at the rear side of the impeller (2) for pressing and fixing the impeller (2) and the shaft body (1).

2. The axial-flow pressing type positioning impeller shafting structure for steam turbines according to claim 1, wherein: A wedge-shaped shaft shoulder (3) is provided on the shaft body (1). A concave wedge-shaped force-applying surface A (4) is provided at one end of the impeller (2), and a convex wedge-shaped force-applying surface (5) is provided at the other end of the impeller (2). The concave wedge-shaped force-applying surface A (4) of the impeller (2) cooperates with the wedge-shaped shaft shoulder (3).

3. The axial-flow compression type positioning impeller shafting structure for steam turbines according to claim 1, characterized in that: The force-applying and tightening assembly includes a tightening bolt (6), a pair of shaft retaining half-rings (7), a cover (8), a threaded retaining ring (9), and a gland (10). A ring groove (11) is arranged on the surface of the shaft body (1). A pair of the shaft retaining half-rings (7) are connected into a whole by bolts, and a pair of the shaft retaining half-rings (7) are both embedded in the ring groove (11). A concave wedge-shaped force-applying surface B (12) is provided on the inner side of the gland (10). The concave wedge-shaped force-applying surface B (12) of the gland (10) cooperates with the convex wedge-shaped force-applying surface (5) of the impeller (2). Ring grooves are provided on the opposite sides of the threaded retaining ring (9) and the cover (8), and the shaft retaining half-ring (7) is located inside the threaded retaining ring (9). The threaded retaining ring (9) and the cover (8) are fixed by bolts. A through hole is provided on the cover (8). The threaded retaining ring (9) is located on the other side of the gland (10). The opposite sides of the gland (10) and the threaded retaining ring (9) are provided with top holes (13). A threaded hole (14) is penetrated through the threaded retaining ring (9). The top holes (13), the threaded hole (14), and the through hole are opposite to each other, and the tightening bolt (6) is installed in the through hole.

4. The axial flow compression type positioning impeller shafting structure for a steam turbine according to claim 1, wherein: A number of equidistant elastic gain notches (15) are provided on the convex wedge-shaped force-applying surface (5) of the impeller (2).

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