Air passage type silencer
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Solution Overview
Problem
Air passage type silencers experience significant pressure loss at high flow rates due to the level difference between ventilation pipes and expansion portions, especially when using porous sound absorbing materials with high surface roughness, which exacerbates the issue.
Innovation Solution
The air passage type silencer design incorporates a level difference that satisfies specific equations (d≥100 μm, d≤25×Sa+193 μm for Sa≤50 μm, and d≤1450 μm for Sa>50 μm) between the ventilation pipe interior wall and the surface of the porous sound absorbing material, optimizing the connection portions to reduce pressure loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a porous sound absorbing material is disposed in the expansion portion, then sound attenuation performance is improved, but pressure loss increases due to high surface roughness at high flow rates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the level difference parameter (d) between the ventilation pipe interior wall and the porous sound absorbing material surface. By setting d within a specific range (100 μm ≤ d ≤ 25×Sa+193 μm), the patent optimizes the balance between sound attenuation and pressure loss characteristics, reducing pressure loss while maintaining acoustic performance at high flow rates.
2Loss of energy
If the diameter of the porous sound absorbing material is made equal to the ventilation pipe diameter to eliminate level difference, then pressure loss is reduced, but pressure loss increases due to high surface roughness of the porous material
Solution Approach 1:
The patent introduces a controlled level difference parameter (d) that satisfies the equation 100 μm ≤ d ≤ 25×Sa+193 μm, where Sa is the arithmetic average height of the porous sound absorbing material surface. This parameter change transforms the problem by showing that an optimal level difference exists that minimizes pressure loss while accounting for surface roughness effects.
Solution Approach 2:
The patent uses the level difference (d) as an intermediary parameter that mediates between the ventilation pipe and the porous sound absorbing material. By controlling this intermediate dimension, the patent resolves the conflict between eliminating level difference and accounting for surface roughness, achieving optimal pressure loss 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 effectively reduces pressure loss at high flow rates by managing the level difference and surface roughness, resulting in improved airflow efficiency and noise attenuation.
Implementation Method 1
a porous sound absorbing material is disposed in an expansion portion so that the sound attenuation performance is improved
Data Source
AI summary
Provided is an air passage type silencer that can reduce pressure loss even in a case where the flow rate of a gas flowing in the air passage type silencer is high. An air passage type silencer includes an inlet-side ventilation pipe, an expansion portion that communicates with the inlet-side ventilation pipe and of which a cross-sectional area is larger than a cross-sectional area of the inlet-side ventilation pipe, and an outlet-side ventilation pipe that communicates with the expansion portion and of which a cross-sectional area is smaller than the cross-sectional area of the expansion portion. A level difference d satisfies Equation (1): d≥100 μm, satisfies Equation (2): d≤25×Sa+193 μm in a case where an arithmetic average height Sa is equal to or smaller than 50 μm, and satisfies Equation (3): d≤1450 μm in a case where the arithmetic average height Sa exceeds 50 μm, where Sa (μm) is an arithmetic average height of a surface on a central side in the expansion portion and d (μm) is an average value of level differences between a ventilation pipe interior wall and the surface on the central side at at least one of a connection portion between the expansion portion and the inlet-side ventilation pipe or a connection portion between the expansion portion and the outlet-side ventilation pipe.