Pipe-in-Pipe Rear Silencer for Compact Exhaust Noise Damping
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Solution Overview
Problem
Conventional rear silencers for combustion engine exhaust systems require significant space to achieve effective low-frequency noise damping, which is a challenge for smaller vehicles with limited space and weight constraints.
Innovation Solution
A pipe-in-pipe arrangement is used for the outlet pipe, featuring a deflection pipe within the silencer housing and an outlet pipe, allowing for a long flow path with shorter overall length through 180° deflections, reducing space requirements while maintaining effective noise damping across frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a long outlet pipe is used to achieve effective low-frequency noise damping, then the noise damping performance is improved, but the construction volume and space requirements increase
Solution Approach 1:
The outlet pipe is designed as a pipe-in-pipe arrangement where an inner pipe is nested within an outer pipe. This allows the exhaust flow to travel a long path through multiple deflections while maintaining a compact overall structure. The inner pipe can be positioned concentrically or eccentrically within the outer pipe, creating a space-efficient configuration that achieves long flow path length without proportionally increasing the silencer volume.
Solution Approach 2:
Instead of extending the outlet pipe in a single linear direction, the design introduces multiple spatial dimensions through deflection sections. The exhaust flow is directed through 180° deflections using deflectors or bends, transforming a one-dimensional linear path into a multi-dimensional folded path. This allows the flow to traverse a long distance within a compact three-dimensional space envelope.
2Object-affected harmful factors
If a long outlet pipe is used for noise damping, then the damping effect is improved, but the weight of the silencer increases
Solution Approach 1:
The nested pipe-in-pipe configuration allows the system to achieve the required flow path length for noise damping without using a single long pipe that would weigh more. By folding the path through nested structures, the total material volume and consequently the weight are reduced while maintaining the acoustic damping performance.
3Volume of moving object
If the outlet pipe is shortened to reduce space requirements, then the construction volume is reduced, but the low-frequency noise damping performance deteriorates
Solution Approach 1:
The invention resolves this contradiction by introducing multiple deflection sections that fold the flow path in three-dimensional space. The outlet pipe includes 180° deflections achieved through deflectors or bent sections, allowing the flow to travel a long effective path while the physical pipe length remains short. This multi-dimensional path folding maintains noise damping performance without requiring extended pipe length.
Solution Approach 2:
The outlet pipe is segmented into multiple sections including straight sections and deflection sections. Each segment contributes to the overall flow path length, and the segmented structure allows compact arrangement while maintaining the cumulative path length necessary for effective low-frequency noise damping.
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 design achieves equivalent low-frequency noise damping to traditional long pipes while being more compact, with additional benefits of reduced flow resistance and noise reduction at higher frequencies.
Implementation Method 1
Through the pipe-in-pipe arrangement, a comparatively long flow path can be realized with short length, which is carried out with the help of suitable deflections. The pipe-in-pipe arrangement can be constructed substantially shorter than a comparable pipe with identical flow length. Investigations have shown that the pipe-in-pipe arrangement achieves damping equivalent to that of a continuous pipe with respect to the low frequencies.
Implementation Method 2
At higher frequencies, an even better damping effect is achieved which is attributed to the cross-sectional jumps in the region of the flow deflections.
Implementation Method 3
the deflection pipe on its closed side comprises a bottom that is concavely curved towards the outlet pipe. Because of this, the through-flow resistance of the silencer can be reduced.
Data Source
AI summary
A silencer, particularly rear silencer, for an exhaust system of a combustion engine, particularly of a motor vehicle, has a housing in which an outlet chamber is located. An outlet pipe arrangement leads out of the housing which on the inlet side is fluidically connected to the outlet chamber. A particularly compact design can be realized if the outlet pipe arrangement is configured as pipe-in-pipe arrangement including at least one deflection pipe closed on one side and arranged in the housing and an outlet pipe led out of the housing.