Acoustic Liners in Electrically Driven Ducted Fan Engine
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Solution Overview
Problem
Electrically driven ducted fan engines face challenges in reducing noise emissions while minimizing aerodynamic drag and weight, as conventional noise reduction strategies for jet engines are not optimal due to differences in thermal profiles and noise sources.
Innovation Solution
The engine incorporates acoustic liners in specific regions such as the interstage, guide vane, and exhaust sections, tuned to specific wavelengths and frequencies, to effectively reduce noise emissions, particularly downstream noise, by targeting dominant noise sources like fan and interaction tones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If acoustic lining is provided throughout the entire housing to maximize noise reduction, then noise emissions are reduced, but aerodynamic drag increases and mass increases
Solution Approach 1:
The patent applies acoustic lining selectively to specific regions where noise generation is most prominent - namely the interstage region between rotor and stator, and the exhaust region downstream of the stator assembly. This localized approach targets the dominant noise sources while avoiding the need for comprehensive lining throughout the entire housing, thereby reducing unnecessary mass and material usage.
Solution Approach 2:
The housing is divided into distinct functional regions: an inlet section upstream of the rotor, an interstage region between the rotor and stator assembly, a guide vane region where guide vanes extend to the inner wall, and an exhaust section downstream of the stator assembly. Acoustic lining is applied to specific segments (interstage and exhaust regions) rather than uniformly across all sections, allowing optimized noise reduction with minimized material usage.
2Object-affected harmful factors
If acoustic lining is provided throughout the entire housing to maximize noise reduction, then noise emissions are reduced, but aerodynamic drag increases
Solution Approach 1:
Acoustic lining is strategically positioned in the interstage region and exhaust region, where noise generation is most intense. This localized placement ensures that noise reduction is achieved where it matters most, while avoiding the installation of lining in regions where it would create unnecessary aerodynamic drag, such as the inlet section and areas critical for airflow efficiency.
Solution Approach 2:
By segmenting the housing into distinct regions and applying acoustic lining only to specific segments (interstage and exhaust), the design achieves effective noise reduction without uniformly increasing drag across the entire engine. The segmentation allows for optimized placement that balances acoustic performance with aerodynamic efficiency.
3Object-affected harmful factors
If conventional jet engine noise reduction strategies are applied to electrically driven ducted fan engines, then fan buzzsaw noise is reduced, but other noise sources become prominent and thermal profiles differ
Solution Approach 1:
The patent adapts noise reduction strategies to the specific characteristics of electrically driven ducted fan engines by changing the approach from conventional jet engine methods. Instead of focusing solely on fan buzzsaw noise, the design addresses the different noise spectrum of electrically driven fans, including higher order modes and interaction tones, by positioning acoustic lining in the interstage and exhaust regions where these noise sources propagate.
Solution Approach 2:
The patent identifies and targets specific local noise sources unique to electrically driven ducted fan engines - particularly interaction tones from rotor-stator interactions and higher order modes in the exhaust region. By placing acoustic lining in these specific regions, the design addresses the adapted noise characteristics of electric propulsion systems rather than relying on conventional jet engine noise reduction approaches.
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 approach achieves significant noise reduction with minimal increase in drag and weight, allowing for more flights and improved economic and community acceptance, while maintaining aircraft efficiency and range.
Implementation Method 1
acoustic liners are provided to the housing in at least one of the interstage region, the guide vane region and the exhaust region
Data Source
AI summary
Disclosed is an electrically driven ducted fan engine, comprising a housing with an inner housing wall, defining a substantially cylindrical inner space and a longitudinal axis, an inlet opening, a rotor with a multitude of rotor blades positioned in the inner space of the housing downstream of the inlet opening, a stator assembly with a multitude of guide vanes extending from a radially central region of the inner space to the inner wall of the housing, and an exhaust opening provided in the housing downstream of the stator assembly, an interstage region defined between the rotor and the stator assembly, a guide vane region defined in which guide vanes extend to the inner wall of the housing and an exhaust section, wherein in at least one of the interstage region, the guide vane region and the exhaust region, acoustic liners are provided to the housing.