Blisk Vibration Detection Using Laser Vibrometer and Optical Path Changer
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Solution Overview
Problem
Blisks, which have blades integrally formed with a disk, pose challenges in detecting unexpected vibration modes during rotation due to their design, as they cannot be intentionally arranged to suppress vibrations like traditional rotor blades, potentially leading to reduced lifespan.
Innovation Solution
A vibration detection device for blisks that includes exciters generating phase-shifted excitation signals, a laser vibrometer for detecting blade vibrations, and an optical path changer to accurately analyze the vibration response of each blade, allowing for the detection of amplitude, phase, and nodal diameters, simulating pressure fluctuations and natural vibration frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If blades are integrally formed with a disk in a blisk, then manufacturing efficiency and structural integrity are improved, but the ability to intentionally arrange blades to suppress vibration is lost
Solution Approach 1:
The patent segments the vibration detection process into multiple measurement points across different blades. By using a plurality of measurement points arranged to measure vibrations of multiple blades simultaneously, the system can analyze vibration characteristics of individual blades within the integrated blisk structure, enabling identification of mistuned blades that would otherwise be indistinguishable in the unified structure.
2Device complexity
If a blisk structure is used, then device complexity is reduced, but measurement precision for detecting individual blade vibrations deteriorates
Solution Approach 1:
The patent applies local quality by positioning measurement points at specific locations on different blades where vibration characteristics can be distinctly measured. The measurement points are strategically arranged to capture local vibration responses of individual blades, allowing precise detection of blade-specific vibration modes despite the integrated blisk structure.
Solution Approach 2:
The patent transitions from measuring only overall blisk vibration to measuring vibration in multiple spatial dimensions by placing measurement points at different radial and circumferential positions on multiple blades. This multi-dimensional measurement approach enables differentiation of individual blade vibrations within the integrated structure.
3Reliability
If vibration measurement is performed on rotating blisk, then operational vibration characteristics are detected, but measurement difficulty increases due to rotation and vibration
Solution Approach 1:
The patent applies preliminary action by pre-positioning multiple measurement points on the blisk blades before rotation begins. The measurement system is configured in advance to track and measure vibrations at these predetermined locations during rotation, enabling continuous monitoring of individual blade vibrations without requiring complex real-time positioning adjustments.
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
Enables accurate detection of vibration responses during blisk rotation, effectively identifying potential vibration modes and evaluating the blisk's vibration characteristics, thereby preventing unexpected vibrations and extending its lifespan.
Implementation Method 1
a laser vibrometer configured to output a laser beam for detecting a vibration of each of the plurality of blades and receive a reflected beam from a target irradiated with the laser beam
Data Source
AI summary
Exciters vibrate blades of a disk of a blisk, using excitation signals of a traveling wave or a backward wave in which a phase is sequentially shifted in a traveling direction or a delay direction. A laser vibrometer outputs a laser beam for detecting a vibration of each of the blades and receives a reflected beam from a target irradiated with the laser beam. An optical path changer is arranged on an optical path of the laser beam and changes an optical path of the laser beam and the reflected beam based on a vibration detection position of a blade designated as an irradiation target for the laser beam from among the blades. A controller detects a vibration response to excitation of the respective blades, from the laser beam and the reflected beam corresponding to the respective blades being excited by the respective exciters.