Motor-Generator Arrangement for Gas Turbine Rotor Distortion Control
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Solution Overview
Problem
Gas turbine engine rotors experience uneven cooling after shutdown, leading to temperature differentials that cause distortion, increased vibration, and potential blade rubbing, which conventional methods only partially address.
Innovation Solution
A motor arrangement with a low input voltage AC motor, a permanent magnet generator, and a temperature sensor, supported by bearings on opposite sides, provides slow rotation to the rotor using a large radial air-gap to minimize cogging torques, and a method to control rotor distortion by determining the rotor's position and speed using a position/speed signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If motors are employed to rotate the engine rotor during cool down, then rotor distortion is controlled, but power consumption and weight increase
Solution Approach 1:
The patent combines the motor and generator into a single integrated assembly where the motor rotates the rotor during cool-down and the generator can harvest energy during engine operation. This merging reduces overall system weight and component count while maintaining the rotor rotation function for distortion control.
Solution Approach 2:
The generator component allows the system to harvest electrical energy during engine operation to offset the power consumption of the motor during cool-down periods. This self-service mechanism reduces net energy requirements by utilizing the engine's own operational energy to support the distortion control function.
2Stability of the object's composition
If motors are employed to rotate the engine rotor during cool down, then rotor distortion is controlled, but device weight increases
Solution Approach 1:
The motor and generator are combined into a single integrated assembly mounted on the engine rotor, sharing common structural support and mounting hardware. This consolidation eliminates duplicate mounting structures and reduces overall assembly weight compared to separate motor and generator installations.
Solution Approach 2:
The integrated motor-generator assembly serves multiple functions: the motor provides rotor rotation during cool-down to prevent distortion, while the generator harvests energy during operation. This multi-functionality eliminates the need for separate systems, reducing total weight.
3Object-generated harmful factors
If a large radial air-gap is used in the generator, then cogging torques are minimized, but generator efficiency decreases
Solution Approach 1:
The patent optimizes the air-gap dimensions and magnetic circuit design to achieve an optimal balance where the air-gap is sufficiently large to reduce cogging torques to acceptable levels while maintaining generator efficiency through improved magnetic material selection and winding configuration.
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
Effectively limits rotor distortion during cool-down by providing slow rotation, reducing temperature differences and vibration, and allowing tighter compressor and turbine blade clearances without the need for auxiliary power units, while operating efficiently in high-temperature environments.
Implementation Method 1
a permanent magnet generator operatively connected to the motor and the rotor and arranged to generate a position/speed signal
Implementation Method 2
a motor operatively connected to the rotor and arranged to provide slow rotation to the rotor
Implementation Method 3
A radial air-gap between the generator stator and the PM assembly can purposely be large to minimize cogging torques
Implementation Method 4
A temperature sensor can be arranged axially between the motor and the generator
Data Source
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AI summary
A motor arrangement (100) includes a shaft (116), a motor (118) with a cage winding (120) fixed in rotation relative to the shaft (116), and a generator (122). The generator (122) includes a permanent magnet assembly (122) fixed in rotation relative to the shaft (116). The permanent magnet assembly (122) and the cage winding (120) are fixed in rotation relative to one another such that the generator (122) generates a sinusoidal AC voltage signal according to an excitation phase applied to the motor (118) for controlling rotor distortion during cool down of a gas turbine engine (10).