Abradable Electrode Capacitive Sensor for Turbomachine Clearance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional capacitive sensors for measuring clearance between rotor vanes and abradable coatings in turbomachines face inaccuracies and noise due to the need for recessed electrodes, which oppose the requirement for close proximity and small electrode size for precise tip-timing measurements, especially in cases of vane penetration into the coating.
Innovation Solution
A capacitive sensor with an abradable electrode material that wears at a rate identical to the abradable coating, eliminating the need for a recess and ensuring accurate, continuous measurement of clearance by aligning the electrode surface with the coating, thereby measuring the exact distance between the vane apex and the inner surface of the coating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the first electrode is positioned recessed from the inner surface of the abradable coating to avoid contact with the vane apex, then the reliability of the sensor is improved, but the measurement precision deteriorates because the measured distance includes the recess depth and does not accurately represent the clearance between the vane apex and the coating surface
Solution Approach 1:
The invention changes the material parameter of the electrode from non-abradable to abradable material with identical wear characteristics to the coating. This allows the electrode surface to remain aligned with the coating surface during operation, eliminating the need for a recess and enabling accurate clearance measurements while maintaining sensor reliability through controlled material wear.
2Measurement precision
If the first electrode is positioned close to the vane apex for precise tip-timing measurements, then the measurement precision is improved, but the reliability deteriorates because the electrode may contact the vane apex and cause mechanical damage
Solution Approach 1:
The electrode material is changed to an abradable material that wears at the same rate as the protective coating. This allows the electrode to be positioned flush with the coating surface, maintaining close proximity for accurate measurements while the controlled wear process prevents harmful contact with the vane apex.
3Duration of action of stationary object
If the first electrode is made of non-abradable material and positioned recessed, then the electrode durability is improved, but the measurement accuracy deteriorates due to the recess depth offset and inability to track coating wear
Solution Approach 1:
The electrode material is changed from non-abradable to abradable material with wear characteristics matching the protective coating. This enables the electrode to maintain alignment with the coating surface throughout operation, automatically compensating for coating wear and providing continuous accurate clearance measurements while maintaining sufficient electrode life.
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
The solution provides precise and continuous clearance measurements, avoiding mechanical stress and ensuring accurate data even during vane penetration, enhancing the reliability of turbomachine performance monitoring.
Implementation Method 1
a first electrode the material of which is abradable so as to get worn upon contacting the vane apex, said material of said first electrode having a degree of wear substantially identical to the wear extent of the material of said abradable coating
Implementation Method 2
a capacitive sensor for measuring the clearance between the apex of the vanes of a rotor and the inner surface of an abradable coating... The second electrode is formed on each vane apex. When a vane comes with the first electrode, the distance is minimum and thus the capacitance is maximum.
Data Source
AI summary
A capacitive sensor for measuring the clearance between the apex of the vanes of a rotor and the inner surface of an abradable coating covering the inner surface of a turbomachine casing, the clearance measuring capacitive sensor including a first electrode the material of which is abradable so as to get worn upon contacting an apex of a vane, the material of the first electrode having a degree of wear substantially identical to the degree of wear of the material of the abradable coating.