Bent Rotor Straightening Using Low-Frequency Induction Heating
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Solution Overview
Problem
Current methods for straightening bent rotors in power generation gas turbines, such as thermal shelf and torch correction, are inefficient and prone to damaging the rotor or blades, and lack precise temperature control, leading to lengthy correction times and potential residual stress issues.
Innovation Solution
A bent rotor straightening method using low-frequency induction heating, which calculates and maintains specific target temperatures to correct bending, employing a low-frequency induction coil wound on the rotor with controlled heating speeds and times to remove residual stress, allowing for precise thermal correction without damaging the blades.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a mechanical load is used to straighten the rotor, then the correction can be applied directly, but there is a large possibility of damage to the rotor on the contact surface
Solution Approach 1:
The patent replaces the mechanical load method with a thermal load method. Instead of applying mechanical force directly to the rotor surface, the invention uses induction heating to apply thermal energy to the bent portion, causing thermal expansion and stress relief that straightens the rotor without mechanical contact, thereby avoiding surface damage while maintaining correction effectiveness
2Stability of the object's composition
If a thermal shelf is used for correction, then the entire rotor can be heated uniformly, but blades may be damaged and correction takes a long time
Solution Approach 1:
The patent applies local quality by using an induction coil to heat only the specific bent portion of the rotor rather than the entire rotor. The coil is positioned to concentrate thermal energy precisely where needed, creating a localized thermal field that affects only the target area while leaving the blades and other portions of the rotor unaffected, thus preventing blade damage while achieving effective correction
3Length of moving object
If a torch is used for partial heating, then the heating can be localized, but it is difficult to heat only desired portions and control the amount of deformation
Solution Approach 1:
The patent implements feedback control by using a temperature sensor to continuously monitor the temperature of the rotor during induction heating. The controller receives temperature information from the sensor and adjusts the heating power accordingly, creating a closed-loop control system that maintains precise temperature control throughout the correction process, enabling accurate control of the deformation amount while heating only the desired portions
4Adaptability or versatility
If individual tests are performed for various cases based on experiences, then correction can be adapted to different situations, but correction takes a long time
Solution Approach 1:
The patent applies parameter changes by systematically varying heating parameters (power, duration, frequency) based on the measured bending amount and rotor characteristics. Rather than performing individual empirical tests, the invention uses a standardized procedure where the controller automatically adjusts heating parameters according to the detected bending severity, maintaining adaptability to different cases while significantly reducing correction time through automated parameter optimization
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method effectively corrects rotor bending by removing residual stress, optimizes thermal treatment, and prevents blade damage, enabling faster and more controlled correction of rotor bending, suitable for various rotor types.
Implementation Method 1
calculating a heating speed when a first target temperature for correcting bending of a rotor using low-frequency induction heating is set; maintaining the first target temperature for a heating time determined on the basis of a diameter of the rotor when the first target temperature is reached, when performing primary thermal correction at the heating speed
Data Source
AI summary
A bent rotor straightening method using low-frequency induction heating and a bent rotor straightening apparatus using the method are proposed. The bent rotor straightening method using low-frequency induction heating according to an embodiment of the present invention includes: calculating a heating speed when a first target temperature for correcting bending of a rotor using low-frequency induction heating is set; maintaining the first target temperature for a heating time determined on the basis of a diameter of the rotor when the first target temperature is reached, when performing primary thermal correction at the heating speed; checking whether a bending amount of the rotor reaches a predetermined critical value in accordance the result of performing the primary thermal correction; and finishing correction of bending of the rotor in accordance with the result of checking the bending amount of the rotor.