Variable Area Fan Nozzle with Acoustic Liner for Noise Reduction
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Solution Overview
Problem
Gas turbine engines face challenges in reducing noise and improving performance, particularly in achieving optimal speed alignment between turbine and fan sections while minimizing noise generation.
Innovation Solution
The implementation of a variable area fan nozzle and a perforated acoustic liner with a honeycomb structure, which includes a gear system for speed reduction and acoustic treatment, reduces noise by controlling the fan bypass flow path pressure ratio and area covered by acoustic liners.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a variable area fan nozzle is implemented to optimize propulsive efficiency, then engine performance is improved, but noise generation increases
Solution Approach 1:
The patent applies acoustic treatment materials (acoustic liners) within the fan nozzle structure to convert the harmful noise generated by optimized fan bypass flow into a beneficial outcome by absorbing and dissipating sound energy, thereby maintaining both high propulsive efficiency and reduced noise signatures
2Object-generated harmful factors
If acoustic treatment is added to reduce noise, then noise levels decrease, but device complexity increases
Solution Approach 1:
The patent applies acoustic treatment selectively in specific regions where noise generation is most problematic, rather than uniformly across the entire engine structure. This localized approach reduces noise effectively while minimizing the added complexity and weight of acoustic materials
3Productivity
If fan bypass flow pressure ratio is increased to improve performance, then propulsive efficiency is enhanced, but noise generation increases
Solution Approach 1:
The patent utilizes a variable area fan nozzle that dynamically adjusts the exit area to optimize the fan bypass flow pressure ratio under different operating conditions. By changing geometric parameters in real-time, the system maintains high propulsive efficiency while managing noise generation through controlled flow characteristics
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 configuration results in reduced noise generation, allowing for a smaller acoustic liner area and improved engine performance by optimizing fan and turbine speeds, thereby enhancing propulsive efficiency and reducing noise levels.
Implementation Method 1
an acoustic treatment of the movable nozzle, the acoustic treatment including an acoustic liner positioned within a bounding structure of the movable nozzle
Implementation Method 2
the acoustic liner is perforated... the acoustic liner includes a honeycomb between two face sheets, and one of the face sheets that faces into a bypass flow path of the fan nozzle is perforated
Data Source
Figure 1
Figure 2~3
AI summary
A gas turbine engine includes a spool and a turbine coupled to drive the spool. A fan is coupled to be driven by the turbine through the spool. A gear assembly is coupled between the fan and the spool such that rotation of the spool drives the fan at a different speed than the spool. A fan nozzle is located downstream from the fan. The fan nozzle includes a variable area nozzle configured to change an exit area of the fan nozzle. An acoustic liner partially lines the fan nozzle.