Induction Radiometry for Thermal Barrier Coating Measurement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for measuring the thermal properties of thermal barrier coatings (TBCs) on metallic base materials are complex, inaccurate, and unable to perform in-situ inspections, making it difficult to assess the durability and mechanical properties of gas turbine engine blades without disassembly.
Innovation Solution
A novel technique using induction heating to generate internal heat in the metallic base material, which diffuses through the TBC, allowing for the measurement of thermal properties by recording the time-dependent temperature changes at the outer surface of the TBC using a pyrometer or similar temperature sensing device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If laser flash technique or other thermal property measurement methods are used, then thermal properties can be measured, but the measurement requires dedicated samples and cannot be performed in-situ on real hardware
Solution Approach 1:
The patent replaces traditional mechanical contact-based thermal measurement methods with induction heating and radiometric temperature measurement. The induction heating coil generates heat within the base material without physical contact, and the pyrometer measures temperature remotely through radiation, enabling non-contact, in-situ measurement on real turbine blades without requiring sample removal or disassembly.
Solution Approach 2:
The patent uses thermal radiation as an intermediary to transfer information about the coating properties. The pyrometer detects thermal radiation from the coating surface, which carries information about the coating's thermal diffusivity and thickness. This radiometric intermediary enables remote, non-contact measurement without direct physical access to the coating.
2Measurement precision
If laser flash technique is applied to very thin free-standing coatings, then measurement can be performed, but additional protective layers must be added and accuracy deteriorates
Solution Approach 1:
Instead of applying heat from the coating surface and measuring temperature rise (laser flash technique), the patent inverts the approach by applying induction heating to the base material and measuring the thermal response through the coating. This inversion eliminates the need for protective layers on the coating surface and improves accuracy for thin coatings by directly measuring the coating's thermal resistance to heat flow from the base material.
3Measurement precision
If existing thermal property measurement methods are used, then coating properties can be determined, but the methods are complex and require disassembly of turbine blades
Solution Approach 1:
The patent replaces complex mechanical measurement systems with a simplified induction heating and radiometric measurement system. The induction coil provides contactless heat application, and the pyrometer provides remote temperature measurement, eliminating the need for mechanical access, disassembly, or complex measurement apparatus while maintaining measurement accuracy.
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 enables accurate, in-situ measurement of thermal diffusivity and coating thickness, reducing the need for calibration and providing sufficient accuracy to inform decisions about the continued use of gas turbine engines without the need for turbine blade overhaul.
Implementation Method 1
induction heating to generate internal heat in the metallic base material
Implementation Method 2
induction heating to generate internal heat in the metallic base material
Implementation Method 3
recording the time-dependent temperature changes at the outer surface of the TBC using a pyrometer or similar temperature sensing device
Data Source
AI summary
A system and method for determining the condition of a thermal barrier coating on a base metal component, comprising the use of an induction coil to input into the metallic base layer through the coating layer, a temporally varying heat waveform, and measuring the temperature of the coating surface layer resulting from the input of the heat waveform using a temperature sensor disposed close to the surface of the coating layer. A controller correlates a signal from the temporally varying output of the temperature sensor with a signal corresponding to the temporally varying heat waveform, to determine the phase angle between the signals. The controller uses a mathematical relationship between the phase angle and the frequency of the heat waveform to determine the thermal properties of the non-metallic coating. Both the thermal diffusivity and the barrier coating thickness can be accurately obtained by this method and apparatus.