Rotating Blade Dynamic Strain Reconstruction via Tip Timing
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Solution Overview
Problem
Current blade tip timing technology can only measure finite displacement and strain at the blade tip, limiting its ability to reconstruct dynamic strain fields under multimodal vibrations, and is not suitable for high-temperature environments where strain gauges have low survival rates.
Innovation Solution
A non-contact dynamic strain field measuring method and system that uses a three-dimensional finite element model, blade tip timing sensors, and a conversion matrix to reconstruct dynamic strains across the entire rotating blade surface and inside, capable of handling multimodal vibrations and high-temperature conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If strain gauges are arranged on a rotating blade to measure dynamic strain, then dynamic strains of finite positions can be measured, but the reliability is poor, continuous working time is short, and survival rate is very low in high-temperature environment
Solution Approach 1:
The patent replaces contact-based strain gauge measurement with non-contact blade tip timing measurement. Instead of using physical strain gauges that attach to the blade surface and suffer from high-temperature damage, the system uses sensors mounted on the engine casing to non-contactly measure blade tip vibration signals, thereby eliminating the reliability issues of strain gauges in high-temperature environments while maintaining dynamic strain measurement capability
Solution Approach 2:
The patent introduces blade tip timing as an intermediary measurement method. Rather than directly measuring strain on the blade with vulnerable strain gauges, the system measures blade tip displacement non-contactly and uses finite element model-based inversion to reconstruct the dynamic strain field, thereby protecting the measurement system from high-temperature damage while obtaining strain information
2Reliability
If blade tip timing sensors are used to measure blade vibration, then non-contact measurement is achieved, but only finite displacement and strain of blade tip can be measured, not the overall strain field
Solution Approach 1:
The patent transforms the measurement from one-dimensional blade tip displacement to three-dimensional full-field strain reconstruction. By measuring blade tip displacement non-contactly and using finite element model-based modal inversion, the system reconstructs the complete dynamic strain field including all spatial positions and multiple strain components (axial, circumferential, shear strains) on the blade surface, thereby obtaining comprehensive strain field information from limited measurement points
Solution Approach 2:
The patent segments the complex strain field measurement problem into manageable parts: (1) non-contact blade tip displacement measurement using blade tip timing, (2) modal parameter extraction from displacement signals, (3) finite element model construction, and (4) dynamic strain field inversion. This segmentation allows the system to reconstruct the complete strain field by combining results from each step, overcoming the limitation of measuring only finite points
3Measurement precision
If current dynamic strain reconstruction method is used under single-modal vibration, then dynamic strain estimation is achieved, but it cannot realize reconstruction under multimodal vibration where maximum dynamic stress point position is unfixed
Solution Approach 1:
The patent makes the measurement system adaptive to dynamic vibration conditions by using modal analysis and finite element model-based inversion. Instead of relying on fixed conversion relationships that only work for single-modal vibration, the system extracts modal parameters from measured displacement signals and dynamically reconstructs the strain field for any vibration mode combination, thereby achieving both high accuracy and versatility under complex multimodal vibration conditions
Data Source
AI summary
The present invention discloses a non-contact dynamic strain field measuring method and system for a rotating blade. The method includes the following steps: establishing a three-dimensional finite element model of a to-be-measured rotating blade, and extracting modal parameters of the three-dimensional finite element model; determining the number and axial mounting positions of blade tip timing sensors; constructing a conversion matrix of finite measuring point displacement and an overall strain field; and acquiring blade tip finite position displacement of the rotating blade based on the blade tip timing sensors, and acquiring, by a dynamic strain, dynamic strains of the rotating blade at any moment, on any position and in any direction based on modal processing of the conversion matrix.