Dual Output Accelerometer Rigid Coupling Transverse Vibration
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Solution Overview
Problem
Dual accelerometers used in gas turbine engines face reliability issues due to signal loss when one piezoelectric crystal stack fails and are prone to signal distortion from transverse vibrations, especially when placed on a single pre-tensioned rod or side by side.
Innovation Solution
A dual output accelerometer design with rigid mechanical coupling between two transducers, either sharing a seismic mass or having separate seismic masses with a bracing element, increases the transverse resonant frequency and stabilizes output channels against high transverse loads, ensuring continued functionality under typical gas turbine engine conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If two piezoelectric crystal stacks are located on a single pre-tensioned bolt to provide two output channels, then device complexity is reduced, but reliability deteriorates because if one crystal stack breaks or the pre-tensioned rod breaks, both signals are greatly reduced or lost
Solution Approach 1:
The invention divides the accelerometer system into two independent transducer assemblies, each with its own pre-tensioned rod and piezoelectric crystal stack. This segmentation ensures that a failure in one assembly does not affect the other, providing true redundancy and maintaining signal reliability while keeping the overall device compact.
2Reliability
If two accelerometers are placed side by side to provide dual output channels, then reliability is improved through redundancy, but the likelihood of simultaneous failure increases because they are both subject to substantially the same conditions
Solution Approach 1:
The invention positions the two transducer assemblies at different locations along the longitudinal axis of the accelerometer housing, separated by a distance of at least 0.5 inches. This spatial separation in the longitudinal dimension reduces their exposure to identical transverse vibration conditions, thereby improving the effectiveness of the redundancy while maintaining compact dimensions.
3Device complexity
If two accelerometers are placed on a single pre-tensioned rod one above the other, then device complexity is reduced, but reliability deteriorates because the pre-tensioned rod may fail under transverse vibrations
Solution Approach 1:
The invention uses two separate pre-tensioned rods, each supporting its own piezoelectric crystal stack and seismic mass assembly. This segmentation eliminates the single point of failure inherent in using a single rod, as each rod independently supports its own transducer assembly, thereby improving reliability under transverse vibration conditions.
4Object-affected harmful factors
If a rigid mechanical coupling is added between transducers to increase transverse resonant frequency, then resistance to transverse vibrations is improved, but device complexity increases
Solution Approach 1:
The rigid mechanical coupling structure serves multiple functions: it provides structural support for the piezoelectric crystal stacks, maintains the spatial separation between transducer assemblies, increases transverse resonant frequency to improve vibration resistance, and facilitates signal extraction. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity.
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 design enhances reliability by maintaining dual output channels under transverse vibrations and reduces the likelihood of both transducers failing simultaneously, providing stable and accurate vibration measurements in harsh engine environments.
Implementation Method 1
The sensor works by providing electrical signals indicative of the compression of the piezoelectric stack between the seismic mass and the supporting base
Data Source
AI summary
There is disclosed a dual output compressive mode accelerometer having first and second output channels, comprising:a supporting base;first and second transducers mounted on the supporting base adjacent to one another, each transducer comprising a piezoelectric element and a seismic mass, the piezoelectric element positioned between the supporting base and the seismic mass; anda rigid mechanical coupling between the first and second transducers, the rigid mechanical coupling coupled to both of the first and second transducers above the supporting base.