Mistuned Compressor Diffuser Pipes via Aero-Dampers
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Solution Overview
Problem
Centrifugal compressors in gas turbine engines experience vibration amplification due to synchronized natural vibration frequencies of diffuser pipes, leading to increased stress and potential damage.
Innovation Solution
The diffuser pipe assembly is designed with subsets of diffuser pipes having distinct natural vibration frequencies through the use of aero-dampers and varying geometries, materials, and stiffness, preventing vibration transfer between pipes by aerodynamically damping specific pipes to create frequency offsets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If diffuser pipes are designed to be stiffer to resist high stresses, then strength and stress resistance are improved, but vibration frequency synchronization and vibration amplification remain problematic
Solution Approach 1:
The patent applies local quality by introducing aero-dampers selectively in certain diffuser pipes (first subset) while leaving others (second subset) without dampers. This creates localized differences in vibration characteristics, allowing specific pipes to be damped while others maintain their natural frequency, thereby preventing synchronized vibration amplification across all pipes while maintaining overall structural strength.
Solution Approach 2:
The patent changes the vibration frequency parameter by introducing aero-dampers that modify the natural vibration frequency of selected diffuser pipes. The aero-dampers create a frequency offset between damped and non-damped pipes, preventing resonance synchronization. This parameter change allows the system to maintain stress resistance while eliminating the harmful synchronized vibration effect.
2Ease of manufacture
If all diffuser pipes have the same natural vibration frequency for uniform construction, then manufacturing simplicity is improved, but vibration transfer and amplification increase
Solution Approach 1:
The patent segments the diffuser pipe population into two distinct subsets: a first subset with aero-dampers and a second subset without aero-dampers. This segmentation creates intentional heterogeneity in vibration characteristics, where damped pipes prevent vibration transfer to undamped pipes, thereby reducing overall vibration amplification while maintaining manufacturing simplicity through modular construction.
Solution Approach 2:
The aero-dampers act as intermediary elements that intervene in the vibration transfer pathway between diffuser pipes. By introducing these intermediary damping elements in select pipes, the patent disrupts the transmission of vibration energy from one pipe to another, preventing the harmful synchronized vibration effect while maintaining overall structural uniformity.
3Reliability
If aero-dampers are added to all diffuser pipes to prevent vibration transfer, then vibration amplification is reduced, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent applies partial action by installing aero-dampers only in the first subset of diffuser pipes rather than all pipes. This partial deployment is sufficient to prevent vibration transfer, as the damped pipes in the first subset create frequency offsets that prevent resonance synchronization with undamped pipes in the second subset, thereby achieving vibration reduction without the complexity of universal dampening.
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 solution effectively reduces vibration amplification and stress on diffuser pipes by mistuning their natural frequencies, thereby enhancing the durability and operational stability of the gas turbine engine.
Implementation Method 1
varying a natural vibration frequency of at least one of the diffuser pipes relative to the adjacent diffuser pipes by aerodynamically damping the at least one of the diffuser pipes to generate a natural vibration frequency offset
Implementation Method 2
diffuser pipes circumferentially distributed around the central axis and configured for diffusing a flow of compressed air received from an impeller
Data Source
AI summary
There is disclosed a diffuser pipe assembly having: a plurality of diffuser pipes circumferentially distributed around the central axis and configured for diffusing a flow of compressed air received from an impeller, the diffuser pipes having a diffuser conduit for directing the flow of compressed air, the diffuser conduit curving between an inlet end and an outlet end along a conduit axis, the diffuser conduit having a baseline surface, a first subset of the diffuser pipes having aero-dampers protruding from the baseline surfaces of their diffuser conduits such that the diffuser pipes of the first subset have a natural vibration frequency different than a natural vibration frequency of at least a second subset of the diffuser pipes.