Gas Turbine Shaft Speed Monitoring Using Blade Jitter Correction
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Solution Overview
Problem
Existing methods for monitoring the rotational speed of gas turbine shafts with moving blades face challenges such as blade jitter, which causes varying errors, and the need for fast and accurate measurements, especially under conditions of shaft acceleration and deceleration, and the presence of missing pulses due to damaged blades.
Innovation Solution
A method that calculates the rotational speed using a single time period measurement and applies a correction factor derived from a previous complete revolution to compensate for blade jitter and missing pulses, allowing for continuous and accurate speed updates with a fast response time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If blade tips are monitored directly to determine rotational speed, then response time is improved, but measurement precision deteriorates due to blade jitter and varying blade spacing
Solution Approach 1:
The system performs preliminary actions by storing blade position information from previous revolutions and using this historical data to predict and compensate for blade jitter in real-time speed calculations, thereby maintaining both fast response and high accuracy
Solution Approach 2:
The system implements feedback by continuously comparing current blade position measurements with stored historical data from previous revolutions, using this feedback loop to calculate correction factors that compensate for blade jitter and improve measurement precision while maintaining rapid response
2Ease of operation
If a gear train is used to connect a phonic wheel to the shaft, then the system can operate remotely from the shaft, but device complexity and weight increase
Solution Approach 1:
The invention extracts the phonic wheel directly from the gear train transmission system and mounts it directly on the shaft, eliminating the need for complex gear trains while maintaining remote operation capability through direct sensor monitoring of blade tips
Solution Approach 2:
The system replaces the mechanical gear train transmission with a direct magnetic sensing system that monitors blade tip positions electronically, substituting mechanical complexity with electronic measurement capabilities
3Ease of operation
If blade movement relative to the shaft is not compensated, then the system is simpler to operate, but measurement precision deteriorates due to varying blade spacing
Solution Approach 1:
The system uses feedback from historical blade position data to calculate correction factors that compensate for blade movement, automatically adjusting speed measurements to maintain high precision without adding operational complexity
Solution Approach 2:
The system dynamically changes the measurement parameters by applying correction factors derived from historical blade position data, adjusting the timing measurements to account for blade jitter and maintain accurate rotational speed calculation
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 approach enables accurate and rapid measurement of gas turbine shaft speed, even under severe conditions, by using historical data to correct for blade movement and missing pulses, improving both accuracy and response time compared to previous methods.
Implementation Method 1
When a blade is moving close to the sensor magnet, eddy currents are generated in the tip of the blade. These eddy currents generate their own magnetic fields which are detected by a coil located in the sensor.
Implementation Method 2
eddy currents generate their own magnetic fields which are detected by a coil located in the sensor
Data Source
Figure 1
Figure 2a~3
Figure 4~5
AI summary
A method (and corresponding apparatus) for monitoring the rotational speed of the shaft of a gas turbine having a number of spaced blades on or rotating with the shaft. The invention compensates for the errors which arise from the relative movement of turbine blade tips by deriving a correction factor for each blade and continually updating that correction factor.