Auxiliary Power Unit Inlet Duct Splitter Noise Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Auxiliary power units on aircraft emit high levels of noise from their gas turbine engines, particularly the compression section, when the vent door is open, posing a concern during ground operations.
Innovation Solution
An inlet duct with at least one splitter positioned between the inlet and outlet ends to sub-divide the airflow into multiple paths, using honeycomb acoustic material and metal housing to reduce noise and provide structural stiffening, while ensuring low inlet flow distortion for the gas turbine engine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the vent door is open to allow airflow to the gas turbine engine, then the engine can operate, but high levels of noise are emitted from the inlet duct
Solution Approach 1:
The inlet duct is divided into multiple flow paths using splitters, creating separate channels for airflow. This segmentation allows acoustic material to be positioned in specific regions where it can effectively reduce noise from the compression section while maintaining overall engine operation capability.
Solution Approach 2:
Acoustic material is introduced as an intermediary element within the inlet duct, positioned between the noise source (compression section) and the external environment. This material absorbs and attenuates noise while allowing airflow to pass through to the engine.
2Object-generated harmful factors
If acoustic material is added to reduce noise, then noise emission decreases, but the structural strength and pressure resistance may be compromised
Solution Approach 1:
The inlet duct employs a composite structure combining rigid structural elements (duct walls, splitters) with acoustic material. This composite design allows the structure to maintain strength and pressure resistance while incorporating noise-reducing acoustic material in strategic locations.
Solution Approach 2:
Acoustic material is positioned locally within the inlet duct at specific locations where noise reduction is most effective, rather than uniformly throughout. This localized approach minimizes the impact on overall structural strength while achieving noise reduction goals.
3Object-generated harmful factors
If splitters are added to sub-divide airflow paths, then noise is reduced and structural stiffening is provided, but device complexity increases
Solution Approach 1:
The inlet duct is segmented into multiple flow paths using splitters, which also serve to stiffen the duct structure. This segmentation approach simultaneously achieves noise reduction by directing airflow away from the compression section and provides structural reinforcement without requiring a completely separate stiffening system.
Solution Approach 2:
The splitters serve multiple functions: they divide airflow paths to reduce noise, provide structural stiffening to the duct walls, and maintain airflow integrity to the engine. 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 solution effectively reduces operational noise and structural pressure extremes, enhancing the performance and efficiency of the auxiliary power unit by minimizing noise emissions and maintaining airflow integrity.
Implementation Method 1
honeycomb acoustic material and metal housing to reduce noise
Data Source
AI summary
An inlet duct for an auxiliary power unit comprises an inlet end, and extends to an outlet end. At least one splitter is positioned within the duct and between the inlet and the outlet end to sub-divide an interior of the duct into plural flow paths.