Optical Blade Tip Clearance Measurement System
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Solution Overview
Problem
Accurately measuring blade tip clearance (BTC) in gas turbine engines is challenging due to axial shifts of the knife edge, which can lead to incorrect measurements and inefficiencies, as existing methods struggle to distinguish the blade tip from surrounding components like the blade shroud.
Innovation Solution
A system comprising multiple transmitters and receivers that transmit optical signals towards the turbine blade tip, capturing reflected signals with photodetectors to compute radial clearance based on the positions and intensity values, allowing for precise determination of the blade tip position and clearance relative to the seal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a probe is configured with a sufficiently large field of view to capture the knife edge when it shifts axially, then the knife edge remains in the field of view, but the probe obtains reflected energy from the blade shroud that changes the calculated BTC value significantly
Solution Approach 1:
The probe system is segmented into multiple functional components: a light source, a beam shaping element, a position-sensitive detector, and signal processing circuitry. This segmentation allows each component to be optimized for its specific function, enabling precise BTC measurement while filtering out unwanted reflections from the blade shroud.
Solution Approach 2:
The beam shaping element creates a localized light pattern that is specifically directed at the knife edge region. By concentrating the optical energy in a specific spatial configuration, the system enhances sensitivity to knife edge position while reducing pickup from surrounding areas like the blade shroud.
2Adaptability or versatility
If the field of view is made too large to accommodate axial shifts, then axial shifts are accommodated, but reflected energy from surrounding components changes the calculated BTC value
Solution Approach 1:
The system dynamically tracks the knife edge position through real-time optical detection and signal processing. The position-sensitive detector continuously monitors the reflected light pattern, allowing the system to adapt to axial shifts while maintaining measurement precision through active compensation rather than relying on a static large field of view.
Solution Approach 2:
The system employs feedback through the position-sensitive detector that provides real-time information about knife edge position. This feedback mechanism allows the system to distinguish between actual knife edge movements and spurious reflections, maintaining measurement accuracy even when accommodating axial shifts.
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
Enhances the precision of blade tip clearance measurement by accounting for axial shifts and reducing interference from surrounding components, leading to improved engine efficiency and reduced wear.
Implementation Method 1
a transmitter that transmits an optical signal towards the target and a receiver that captures the optical signal after it is reflected by the target
Implementation Method 2
the receiver includes a photodetector that captures the optical signal and provides an electrical signal
Data Source
Figure 1
Figure 2
Figure 2A
AI summary
Disclosed is a first transmitter (TX) that transmits a first optical signal towards a target, a plurality of receivers (RX) that receive the first optical signal after the first optical signal is reflected by the target and each provides a respective received optical signal, at least one photodetector that receives the received optical signals and provides at least a first electrical signal, and a processor that receives the first electrical signal to compute a position of the target relative to a baseline position based on: a first position of a first receiver of the plurality of receivers, a second position of a second receiver of the plurality of receivers, the first electrical signal. The processor computes a clearance between the target and a component (242) based on a third position of a third receiver, a fourth position of a fourth receiver and a second electrical signal.