Compression-Molded Fiber Inlet Duct for Intake Noise Reduction
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Solution Overview
Problem
Existing inlet ducts for internal combustion engines are inadequate in reducing intake noise across a wide frequency range, as they primarily focus on specific frequencies rather than a broader spectrum.
Innovation Solution
The inlet duct incorporates a duct member made of compression-molded fiber material with a main body featuring high-compression and low-compression portions, where the low-compression portions extend throughout the axial direction, providing air permeability at positions corresponding to antinodes of sound waves to suppress standing wave generation, while high-compression portions restrict air passage and minimize airflow resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the inlet duct uses soft portions with air permeability to reduce standing wave noise, then noise reduction at specific frequencies is improved, but the noise reduction effectiveness is limited to specific frequencies rather than a wide frequency range
Solution Approach 1:
The inlet duct wall is segmented into alternating high-compression portions and low-compression portions along the axial direction. The low-compression portions (with air permeability 1-100 cm³/cm²·s) are positioned to correspond to antinodes of standing waves at multiple frequencies, while high-compression portions (with air permeability 0 cm³/cm²·s) are positioned at nodes. This segmentation allows the duct to suppress standing waves across a wide frequency range by targeting multiple frequency components simultaneously.
Solution Approach 2:
Different portions of the inlet duct wall are given different compression ratios to create localized properties. The low-compression portions have higher air permeability to allow sound wave passage and suppress standing waves, while the high-compression portions have lower air permeability to maintain structural integrity and minimize airflow resistance. This local differentiation enables the duct to address multiple frequency components effectively.
2Object-affected harmful factors
If low-compression portions are added to reduce standing wave noise, then noise reduction capability is improved, but airflow resistance and pressure loss may increase
Solution Approach 1:
The duct wall is divided into alternating high-compression and low-compression portions, ensuring that low-compression portions (which provide noise reduction) occupy only a portion of the circumferential area rather than the entire circumference. This segmentation allows sound wave suppression while maintaining adequate airflow paths through the high-compression portions, thus limiting the increase in airflow resistance and pressure loss.
3Object-affected harmful factors
If the inlet duct wall is made entirely of soft material with air permeability, then standing wave suppression is improved, but structural strength and rigidity are reduced
Solution Approach 1:
The duct wall is segmented into high-compression portions with compression ratio of 80-100% ( providing structural strength) and low-compression portions with compression ratio of 20-70% (providing air permeability for noise reduction). By distributing these portions alternately along the axial direction, the duct maintains overall structural integrity while achieving effective standing wave suppression at multiple frequencies.
Solution Approach 2:
Different compression ratios are applied to different portions of the duct wall to create localized properties matching functional requirements. High-compression portions provide the structural strength and rigidity needed for duct integrity, while low-compression portions provide the air permeability necessary for sound wave passage and standing wave suppression.
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 effectively reduces intake noise across a wide frequency range while limiting airflow resistance and pressure loss, enhancing the overall noise reduction and structural strength of the duct.
Implementation Method 1
the at least one low-compression portion extends throughout a length in the axial direction of the main body
Implementation Method 2
some of the sound wave of the intake air passes through the soft portion. This suppresses the generation of a standing wave of the sound wave of the intake air, thereby reducing the intake noise
Data Source
AI summary
An inlet duct for an internal combustion engine includes a duct member made of a compression molded fiber material. The duct member includes a main body and end portions provided on opposite sides in an axial direction of the main body. The main body includes at least one high-compression portion and at least one low-compression portion, which is made through compression molding at a compression ratio lower than that of the at least one high-compression portion. The at least one low-compression portion extends throughout a length in the axial direction of the main body.