Gas Turbine Blade Array with Nonuniform Harmonics
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Solution Overview
Problem
Existing noise reduction methods for gas turbine engines, such as shifting harmonics to higher orders and using active acoustic liners, are maintenance intensive and inefficient, as new engine designs often generate decay-prone harmonics too close to the inlet for effective decay, and passive methods are lacking.
Innovation Solution
Configuring the fan blades with physical nonuniformities such as pitch angles and angular offsets to generate higher order decay-resistant harmonics, which are then attenuated by a shallower acoustic liner, reducing the size and weight of the engine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If decay-prone harmonics are generated by the fan, then combination tone noise is reduced, but the harmonics are generated too close to the inlet for effective decay
Solution Approach 1:
The patent changes the harmonic order parameter from decay-prone (lower order) to decay-resistant (higher order) harmonics. By configuring blade physical nonuniformities to generate higher order harmonics instead of decay-prone harmonics, the noise attenuation mechanism shifts from relying on natural decay over distance to using an acoustic liner that can effectively attenuate the generated harmonics regardless of their proximity to the inlet.
2Object-affected harmful factors
If active acoustic liners are used to attenuate harmonics, then noise reduction is achieved, but maintenance intensity increases and energy consumption increases
Solution Approach 1:
The patent employs passive acoustic liners that automatically attenuate decay-resistant harmonics without requiring external power sources or active control systems. The liners work passively through their acoustic properties, eliminating the need for electricity, moving components, or complex maintenance associated with active noise control systems.
3Ease of repair
If passive acoustic liners are used, then maintenance is reduced, but the liners must be deeper increasing engine size and weight
Solution Approach 1:
The patent changes the harmonic characteristics (to higher order decay-resistant harmonics) in a way that allows shallower acoustic liners to be effective. The deeper liners would be required only for decay-prone harmonics; the new approach with decay-resistant harmonics enables the use of shallower, lighter liners while maintaining noise attenuation effectiveness.
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
Effectively mitigates combination tone noise by generating and attenuating higher order harmonics, reducing noise without the need for moving components or electricity, thus improving maintenance efficiency and engine performance.
Implementation Method 1
an acoustic liner positioned radially interior to an outer wall of the nacelle in the inlet. The acoustic liner is configured to attenuate an amplitude of a plurality of decay-resistant harmonics of the rotor
Data Source
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AI summary
A rotor for a gas turbine engine, comprising a rotor disk (50); and a plurality of blades (52) extending radially outward from the rotor disk (50), at least one blade (52) having a physical nonuniformity, the blades (52) being distributed about the rotor disk (50) based on any physical nonuniformities of the blades (52) to generate at least one decay-resistant harmonic.