Flex Circuit Capacitance Sensor for Rotary Machine Clearance Monitoring
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Solution Overview
Problem
Existing clearance monitoring systems in rotary machines face installation difficulties and inefficiencies due to the thickness and rigidity of capacitive sensors, which can lead to damage and reduced performance, as they require larger gaps that may compromise turbine efficiency and safety.
Innovation Solution
A flex circuit capacitance sensor with flexible layers, including a capacitance sensing layer, shielding layer, and ground layer, is mounted between the rotatable and stationary members, providing a thin and flexible design that conforms to surfaces and minimizes interference with fluid flow, eliminating the need for drilling and reducing the risk of damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional capacitive sensor is used for clearance monitoring, then clearance measurement capability is provided, but the sensor thickness and rigidity require larger gaps that compromise turbine efficiency and may lead to sensor damage
Solution Approach 1:
The patent applies this principle by replacing rigid capacitive sensors with flexible sensors that can be mounted on the turbine blade surface. The flexible sensor conforms to the blade contour and maintains thin profile, eliminating the need for large clearance gaps while preventing sensor damage from blade-shroud contact. This directly resolves the contradiction by enabling accurate clearance measurement without compromising reliability.
Solution Approach 2:
The patent changes the physical state of the sensor from rigid to flexible, fundamentally altering its mechanical properties. This parameter change allows the sensor to adapt to dynamic clearance conditions without breaking, while maintaining measurement precision. The flexible sensor can withstand compression and deformation that would damage rigid sensors, thus resolving the reliability issue.
2Measurement precision
If a conventional capacitive sensor is used for clearance monitoring, then clearance measurement capability is provided, but installation requires drilling holes through shroud wall which is difficult, time consuming, and weakens the shroud wall
Solution Approach 1:
The flexible sensor can be directly mounted on the turbine blade surface using adhesive or other simple fixation methods, eliminating the need for drilling holes through the shroud wall. This dramatically simplifies installation, reduces installation time, and avoids weakening the shroud structure, while maintaining measurement precision through the flexible sensor's ability to conform to the blade surface.
Solution Approach 2:
The patent replaces the mechanical drilling and threading installation method with a simpler adhesive mounting process. This substitution eliminates complex installation procedures and structural modifications, making the manufacturing process easier while achieving the same measurement function.
3Ease of operation
If the gap between turbine blade and shroud is increased to accommodate sensor thickness, then sensor installation is possible, but the gap becomes too large for optimum turbine performance
Solution Approach 1:
The flexible sensor maintains a thin profile that does not require increasing the clearance gap. It can be mounted directly on the blade surface with minimal thickness, allowing the turbine to operate at optimal efficiency while enabling sensor installation. This resolves the contradiction by making installation feasible without sacrificing turbine performance.
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 flexible design allows for accurate clearance monitoring without compromising turbine performance, reduces installation time and complexity, and minimizes the risk of sensor damage, enhancing operational efficiency and safety by maintaining optimal clearance without the need for extensive modifications to the shroud wall.
Implementation Method 1
a capacitive sensor for clearance monitoring in rotary machines. The capacitive sensor determines the clearance between the turbine blades and the shroud
Data Source
AI summary
Systems, methods, and apparatus for monitoring clearance in a rotary machine are provided. According to one embodiment of the invention, there is disclosed a method for monitoring clearance between a rotatable member and a stationary member in a rotary machine. The method may include providing a flex circuit capacitance sensor. The flex circuit capacitance sensor may include at least one capacitance sensing layer, at least one shielding layer adjacent to the capacitance sensing layer, at least one ground layer adjacent to the shielding layer, and a set of conducting leads connected to the capacitance sensing layer. Further, the method may include mounting the capacitance sensor between a portion of the rotatable member and a portion of the stationary member. Clearance may be determined between the rotatable member and the stationary member based at least in part on a capacitance indication from the capacitance sensor.