Turbine Blade Crack Localization Using Vibration Mode Changes
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Solution Overview
Problem
Turbine blades, particularly those with a long length to width ratio, are susceptible to vibration and high cycle fatigue, making in situ measurement of cracks difficult and inaccurate, leading to frequent inspections and conservative operation to prevent unexpected failures.
Innovation Solution
A method and system for determining the location and size of cracks in turbine blades by analyzing changes in first and second vibration conditions compared to baseline conditions, using sensors to measure blade vibrations and a processor to calculate displacement and estimate crack size based on vibration mode changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If frequent inspections and conservative operation are employed to prevent blade failure, then reliability is improved, but productivity deteriorates due to increased downtime and reduced operational flexibility
Solution Approach 1:
The system performs preliminary detection of cracks and damage in blades before they lead to failure. By continuously monitoring vibration conditions and comparing them to baseline values, the system identifies potential issues early, allowing for planned maintenance during scheduled outages rather than unexpected failures or overly conservative operation.
Solution Approach 2:
The system establishes a feedback loop by continuously measuring blade vibration conditions, comparing them to baseline values, and providing information about crack location and size. This feedback enables operators to make informed decisions about blade condition without relying on frequent manual inspections or conservative operational limits.
2Device complexity
If in situ measurement methods are used to detect cracks in blades, then device complexity is reduced, but measurement precision deteriorates due to difficulty in obtaining accurate readings
Solution Approach 1:
The system utilizes mechanical vibration characteristics of the blades as the measurement principle. By analyzing changes in vibration conditions (frequency, amplitude, mode shapes) of the blades during operation, the system can detect cracks and damage without requiring direct physical access to the blade surfaces or complex in-situ measurement equipment attached to the blades themselves.
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
Enables accurate and efficient detection of cracks, allowing for timely maintenance and reducing the risk of blade failure by providing precise location and size estimation of cracks, even in smaller sizes that could lead to mechanical separation.
Implementation Method 1
measuring a time of arrival of a tip of the blade at an angular position in a rotation, using the time of arrival to calculate a displacement of the tip of the blade
Implementation Method 2
determining a first mode vibration condition and a second mode vibration condition for each of the blades in the row of rotating blades based on the measured parameter
Data Source
AI summary
A method of determining the location and size of a crack in a blade includes measuring a time of arrival of a tip of the blade at an angular position in a rotation, using the time of arrival to calculate a displacement of the tip of the blade, and using the displacements to calculate a first vibration condition and a second vibration condition for the blade. The method also includes comparing the first vibration condition and the second vibration condition for the blade to a predetermined baseline first vibration condition and a predetermined baseline second vibration condition for the blade to determine a change in the first vibration condition and a change in the second vibration condition, and using the magnitude of the change in the second vibration condition relative to the change in the first vibration condition to determine the likely location of the crack and using the magnitude of the change in the first vibration condition and the change in the second vibration condition to determine the size of the crack.