Steam turbine rotor demagnetization method
By combining DC and AC demagnetization methods, the turbine rotor shaft and blades are demagnetized in stages, solving the problems of difficult operation and poor results in turbine rotor demagnetization, and achieving efficient and safe demagnetization.
Patent Information
- Application Number
- CN202511681530.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-17
- Publication Date
- 2026-02-10
AI Technical Summary
Existing technologies are difficult to demagnetize turbine rotors quickly and efficiently, especially rotor blades, and conventional methods suffer from operational difficulties and poor demagnetization results.
The rotor shaft ends are demagnetized using a DC demagnetization method, and the coils are alternately connected in positive and negative directions to disrupt the magnetic domain arrangement. Then, the rotor blades are demagnetized using an AC demagnetization method through a columnar iron core until the residual magnetism meets the requirements.
It achieves rapid, thorough, and uniform rotor demagnetization, with accurate measurement results and simple operation, significantly improving demagnetization efficiency and safety while reducing costs.
Smart Images
Figure CN121508378A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of demagnetization, and particularly relates to a steam turbine rotor demagnetization method. BACKGROUND
[0002] During use, a steam turbine rotor may have a magnetic ring phenomenon, and rotor magnetization is one of important reasons causing steam turbine vibration. After the steam turbine rotor is magnetized, a magnetic field is formed on the rotor shaft, one end of the shaft is S level, the other end is N level, and a complex and much higher than required residual magnetic field is also formed on the rotor blades. If the blades are disassembled one by one and then demagnetized, the demagnetization effect is better, but because the number of rotor blades is large, and the precision is difficult to guarantee after disassembly and reinstallation, this method is not feasible. Because the magnetic field of the rotor blades is complex and the gap between the steam turbine rotor blades is small, other conventional demagnetization methods are also difficult to implement, and the demagnetization effect is not ideal. SUMMARY
[0003] The present application solves the technical problem of providing a steam turbine rotor demagnetization method which is simple to operate and can quickly and efficiently complete steam turbine rotor demagnetization.
[0004] The technical scheme adopted by the present application to solve the technical problem is: a steam turbine rotor demagnetization method, comprising the steps of:
[0005] S1, rotor shaft demagnetization: DC coils are respectively wound on both ends of the rotor shaft, and then the two ends of the rotor shaft are sequentially demagnetized by a demagnetizer using a DC coil method until the residual magnetism meets the requirements; wherein, during the demagnetization process, the demagnetizer connection terminals are alternately connected in positive and negative directions, so that the magnetic field generated by the DC coil alternately changes the magnetic pole;
[0006] S2, rotor blade demagnetization:
[0007] S21, winding a wire on a columnar core to form an electromagnetic coil;
[0008] S22, abutting one end of the columnar core against one side of the end of the rotor blade, and then passing alternating current into the wire to make the columnar core an electromagnet, and demagnetizing the rotor blade by a demagnetizer using an alternating current demagnetization method until the residual magnetism meets the requirements;
[0009] S23, sequentially completing the demagnetization of the remaining rotor blades in the manner of step S22.
[0010] Preferably, the residual magnetism of the rotor shaft and the rotor blades is less than 10 Gauss.
[0011] Preferably, when step S2 is performed, the rotor blades are sequentially demagnetized in the order from long to short according to the length of the rotor blades.
[0012] Preferably, when step S2 is performed, the cylindrical core abuts at the end of the rotor blade at the abutment of the adjacent rotor blade.
[0013] Preferably, the rotor shaft demagnetization parameters are: the DC coil is wound by a φ20mm copper core cable, the number of turns of the DC coil is 8 turns, the coil ellipse is 1.5m*0.7m, the demagnetization current is DC2300A, and the demagnetization time is 2min.
[0014] Preferably, the rotor blade demagnetization parameters are: the wire is a φ10mm copper core cable, the number of turns is 8 turns, the demagnetization current is AC1200A, and the demagnetization time of each rotor blade is 5-10s.
[0015] The method of the present application first uses the DC demagnetization method to demagnetize the two ends of the rotor shaft, and then demagnetizes the blades, eliminating the largest interference source. After the shaft is demagnetized, the entire rotor provides a background environment close to "magnetic neutrality". In this environment, when the blades are demagnetized, the data measured by the gauss meter purely reflects the residual magnetism of the blades themselves, and will not be disturbed by the strong background magnetic field of the shaft. This makes the measurement result more accurate, the demagnetization process more controllable, and the final effect more thorough and uniform. In addition, during the demagnetization process of the rotor shaft, there will be a change in the magnetic poles at both ends of the rotor shaft, so during the demagnetization process, the positive and negative terminals of the demagnetization machine are alternately connected, so that the magnetic field generated by the DC coil changes the magnetic pole alternately, to disrupt the magnetic domain arrangement of the rotor shaft, further reduce the residual magnetic field strength, and ensure the demagnetization effect. In the subsequent rotor blade demagnetization process, the present application uses AC demagnetization according to the characteristics of the blade magnetic field, and abuts one end of the magnetic flux passing through the cylindrical core at the end of the rotor blade 12, thereby constructing an efficient and concentrated magnetic circuit. Not only does it solve the operation problem of the narrow space between the rotor blades and the difficulty of approaching the tool, but it also realizes precise and deep demagnetization of a single blade, avoids magnetic field interference and cross-influence, and significantly improves the safety and efficiency of the demagnetization operation due to its few contact points and simple operation. Overall, the method of the present application can quickly and efficiently complete the demagnetization of the steam turbine rotor, and the demagnetization cost is low. BRIEF DESCRIPTION OF DRAWINGS
[0016] Figure 1 is the rotor blade magnetic field distribution;
[0017] Figure 2 is a rotor shaft demagnetization schematic diagram;
[0018] Figure 3 is a rotor blade demagnetization schematic diagram;
[0019] Shown in the figure: steam turbine rotor 1, DC coil 3, demagnetization machine 4, cylindrical core 5, wire 6, rotor shaft 11, rotor blade 12, abutment 13. DETAILED DESCRIPTION
[0020] The application will be further described below in connection with the accompanying drawings and examples.
[0021] In practice, the applicant has measured that the residual magnetism of the root of the rotor blade of the steam turbine rotor 1 is low and meets the requirements, while the residual magnetism of the tip of the rotor blade is high and higher than the required value. The longer the length of the blade is, the higher the residual magnetism of the tip is. As shown in the figure, the applicant has found that the magnetic field distribution of the rotor blade is also relatively complex, and the root of the blade and the tip of the blade form S and N poles of the magnetic field, and the left and right sides of the tip of the blade also form S and N poles of the magnetic field, which causes great difficulty in demagnetization. Specifically, since the gap between the rotor blades is small, the length of the cable used by the coil is long, and the cable needs to be wound in the gap between each blade for demagnetization, which is difficult to operate. Figure 1
[0022] As shown in the figure, the steam turbine rotor demagnetization method of the application comprises the steps of: Figure 2 、 Figure 3 As shown in the figure, the steam turbine rotor demagnetization method of the application comprises the steps of:
[0023] S1, demagnetize the rotor shaft: DC coils 3 are wound on both ends of the rotor shaft 11, and then the DC coil method is used to demagnetize both ends of the rotor shaft 11 by the demagnetizer 4 until the residual magnetism meets the requirements; wherein, during the demagnetization process, the positive and negative terminals of the demagnetizer are alternately connected, so that the magnetic poles of the magnetic field generated by the DC coil alternately change;
[0024] S2, demagnetize the rotor blade:
[0025] S21, wind the wire 6 on the columnar core 5 to form an electromagnetic coil;
[0026] S22, abut one end of the columnar core 5 on one side of the tip of the rotor blade 12 (the end away from the rotor shaft), and then input alternating current to the wire 6, so that the columnar core 5 becomes an electromagnet, and the rotor blade is demagnetized by the demagnetizer using the alternating current demagnetization method until the residual magnetism meets the requirements;
[0027] S23, complete the demagnetization of the remaining rotor blades 12 in the same way as step S22.
[0028] The method of the application firstly demagnetizes the two ends of the rotor shaft by using the direct current demagnetization method, and then demagnetizes the blades, thereby eliminating the greatest interference source. After the rotor shaft is demagnetized, the entire rotor provides a background environment close to "magnetic neutrality", and in this environment, when the blades are demagnetized again, the data measured by the gauss meter purely reflects the residual magnetism of the blades, and will not be disturbed by the superposition of the strong background magnetic field of the rotor shaft. This makes the measurement result more accurate, the demagnetization process more controllable, and the final effect more thorough and uniform. In addition, during the demagnetization process of the rotor shaft, the magnetic pole of the rotor shaft at both ends will change, so during the demagnetization process, the positive and negative connection terminals of the demagnetization machine are alternately connected, so that the magnetic field generated by the direct current coil alternately changes the magnetic pole of the rotor shaft, thereby disrupting the magnetic domain arrangement of the rotor shaft and further reducing the residual magnetic field strength, thereby ensuring the demagnetization effect. In the subsequent rotor blade demagnetization process, the application adopts alternating current demagnetization according to the characteristics of the blade magnetic field, and abuts one end of the columnar iron core through which the magnetic flux passes against the end of the rotor blade 12, thereby constructing an efficient and concentrated magnetic circuit. Not only does it solve the operation problem of the narrow space between the rotor blades and the difficulty of approaching the tooling, but it also realizes precise and deep demagnetization of a single blade, avoids magnetic field interference and cross-influence, and at the same time, due to the small number of contact points and simple operation, it significantly improves the safety and efficiency of the demagnetization operation.
[0029] In order to better ensure the normal operation of the steam turbine, preferably, the residual magnetism of the rotor shaft and the rotor blades is less than 10 Gauss.
[0030] When demagnetizing the rotor blades, the demagnetization sequence can be from long to short, from short to long, or of course not in length order. The applicant found in the demagnetization process that the longer the length of the rotor blade, the greater the residual magnetism at the end thereof. Therefore, preferably, when performing step S2, the rotor blades are demagnetized in order from long to short according to the length of the rotor blades. It has been proved in practice that compared with other ways, this way can most effectively reduce the background magnetic field strength of the entire rotor, thereby avoiding secondary magnetic pollution of the demagnetized short blades by the long blades, and can further improve the demagnetization effect and efficiency.
[0031] As shown in Figure 1 , preferably, when performing step S2, the abutment of the columnar iron core at the end of the rotor blade is at the abutment 13 between the adjacent rotor blades. Compared with other positions, the above-mentioned way can better ensure the demagnetization effect of the rotor blades.
[0032] In the application, specifically, the rotor shaft demagnetization parameters are that the DC coil is wound by a φ20mm copper core cable, the DC coil turns are 8, the coil ellipse is 1.5m (major axis) x 0.7m (minor axis), the demagnetization current is DC2300A, and the demagnetization time is 2min; the rotor blade demagnetization parameters are that the wire is a φ10mm copper core cable, the winding turns are 8, the demagnetization current is AC1200A, and the demagnetization time of each rotor blade is 5-10s.
Claims
1. A method for demagnetizing a steam turbine rotor, characterized in that, Including the following steps: S1. Rotor shaft demagnetization: DC coils are wound at both ends of the rotor shaft, and then the two ends of the rotor shaft are demagnetized sequentially using the DC coil method through a demagnetizer until the residual magnetism meets the requirements; during the demagnetization process, the terminals of the demagnetizer are alternately connected in opposite directions, so that the magnetic poles of the magnetic field generated by the DC coil change alternately. S2, Rotor blade demagnetization: S21. Wind wires around a cylindrical iron core to form an electromagnetic coil; S22. One end of the columnar iron core is abutted against the end of the rotor blade, and then AC is passed through the wire to make the columnar iron core an electromagnet. The rotor blade is demagnetized by AC demagnetization using a demagnetizer until its residual magnetism meets the requirements. S23. Demagnetize the remaining rotor blades in sequence according to step S22.
2. The turbine rotor demagnetization method as described in claim 1, characterized in that, The residual magnetism of both the rotor shaft and the rotor blades is required to be less than 10 Gauss.
3. The turbine rotor demagnetization method as described in claim 1, characterized in that, During step S2, the rotor blades are demagnetized sequentially from longest to shortest, according to their length.
4. The turbine rotor demagnetization method according to any one of claims 1 to 3, characterized in that, During step S2, the columnar iron core abuts against the end of the rotor blade at the junction with the adjacent rotor blade.
5. The turbine rotor demagnetization method as described in claim 1, characterized in that, The demagnetizing parameters for the rotor shaft are as follows: the DC coil is wound with φ20mm copper core cable, the number of turns of the DC coil is 8, the coil ellipse is 1.5m×0.7m, the demagnetizing current is DC2300A, and the demagnetizing time is 2min.
6. The turbine rotor demagnetization method as described in claim 1, characterized in that, The demagnetizing parameters for the rotor blades are as follows: the conductor is a φ10mm copper core cable with 8 turns, the demagnetizing current is AC1200A, and the demagnetizing time for each rotor blade is 5-10s.