Blade Vibration Frequency Determination Using Single Probe and Bearing Signals
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Solution Overview
Problem
Existing methods for determining vibration frequencies and amplitudes of rotating blades in gas turbine engines face challenges such as complex and expensive telemetry systems, undersampling issues with blade tip timing methods, and impracticality of multiple probes, especially in service environments.
Innovation Solution
A method that combines blade displacements from a single stationary timing probe with vibration signals from the rotor support structure to determine vibration frequencies and amplitudes, using Fourier transforms and comparison with predicted vibration modes to identify and verify blade vibration frequencies and amplitudes, reducing the need for multiple probes and complex telemetry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple strain gauges are mounted on rotating blades with telemetry systems, then measurement precision of vibration frequencies and amplitudes is improved, but device complexity and cost increase significantly
Solution Approach 1:
The invention extracts the vibration measurement function from the complex telemetry system and relocates it to the stationary casing through blade tip timing probes. This separates the measurement function from the rotating components, eliminating the need for complex telemetry systems while maintaining measurement capability.
Solution Approach 2:
The invention introduces blade tip timing probes as intermediaries mounted on the stationary casing to measure blade tip positions. These probes act as mediators between the rotating blades and the measurement system, converting blade tip positions into measurable signals without requiring direct mounting on the blades.
2Device complexity
If blade tip timing probes are used to measure blade vibrations, then device complexity is reduced, but measurement precision deteriorates due to undersampling below Nyquist frequency
Solution Approach 1:
The invention merges blade tip timing data with bearing vibration signals to overcome the undersampling limitation. By combining the complementary information from both measurement sources, the system achieves accurate vibration frequency identification without requiring the probe sampling rate to exceed the Nyquist frequency.
Solution Approach 2:
The invention uses the bearing vibration signals as feedback to validate and correct the blade tip timing measurements. The bearing signals provide reference information about the actual vibration frequencies, allowing the system to resolve ambiguities in the undersampled blade tip data.
3Measurement precision
If multiple timing probes are deployed to improve measurement accuracy, then measurement precision is improved, but ease of operation deteriorates due to inconvenience in engine testing and impracticality in service
Solution Approach 1:
The invention extracts the essential measurement function from multiple probes and concentrates it in a single probe combined with bearing vibration sensors. This reduces the number of components that need to be installed and operated while maintaining measurement capability through the complementary data sources.
Solution Approach 2:
The single timing probe combined with bearing vibration sensors serves multiple functions: measuring blade tip positions, detecting vibration frequencies, and providing reference signals. This multi-functionality eliminates the need for separate multiple probes while achieving comprehensive measurement coverage.
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 approach allows for accurate determination of blade vibration frequencies and amplitudes with reduced complexity and cost, using a single probe and accessible sensors, suitable for both testing and in-service applications, while overcoming undersampling and ambiguity issues.
Implementation Method 1
measure the time at which a blade passes each probe. This time is compared with the time at which the blade would have passed the probe if it had been undergoing no vibration
Implementation Method 2
converting a vibration signal detectable at the support structure into a vibration frequency spectrum
Implementation Method 3
converting a vibration signal detectable at the support structure into a vibration frequency spectrum
Data Source
AI summary
A method is provided for determining vibration frequencies of rotating blades mounted on a rotor which rotates relative to and is supported by a rotor support structure. The method includes the steps of:(a) determining possible vibration frequencies of the blade from blade displacements corresponding to the times at which a blade passes a stationary timing probe;(b) converting a vibration signal detectable at the support structure into a vibration frequency spectrum; and(c) identifying the blade vibration frequency by matching a peak in the vibration frequency spectrum with one of the possible blade vibration frequencies.