Segmented Honeycomb Structure for DPF Thermal Stress Reduction
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Solution Overview
Problem
Honeycomb structures used in diesel particulate filters (DPFs) face issues with thermal shock fractures and melting of partition walls due to uneven temperature distribution, particularly on the exhaust gas outlet side, leading to increased pressure loss and reduced exhaust gas purification efficiency.
Innovation Solution
A honeycomb structure design where cells have the same overall length in the fluid flow direction with displacement in the fluid flow direction, resulting in unevenness on the end faces, allowing for improved heat transfer and reduced super temperature rises by ensuring all cells have the same length and uniform pressure loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a honeycomb structure is used as a DPF with length of 250 mm or more, then the filtration capacity is improved, but thermal stress increases remarkably causing defects such as cracks
Solution Approach 1:
The honeycomb structure is divided into multiple segments along the fluid flow direction, with each segment having partition walls that may have different lengths. This segmentation allows the structure to handle thermal expansion differently in various regions, reducing overall thermal stress while maintaining the required filtration capacity of 250 mm or more.
Solution Approach 2:
Different partition walls within the same honeycomb structure have different lengths, creating local variations in thermal mass and heat transfer characteristics. This local quality variation helps distribute thermal stress more evenly throughout the structure, preventing concentration of stress at specific locations while maintaining adequate filtration capacity.
2Quantity of substance
If the length of honeycomb structure is increased to 150 mm or more, then the filtration performance is improved, but heat concentrates on the exhaust gas outlet side causing super temperature rise
Solution Approach 1:
By segmenting the honeycomb structure into multiple sections with varying partition wall lengths, the heat generation and heat dissipation are distributed more evenly along the fluid flow path. This prevents the concentration of heat at the outlet side while maintaining the required filtration performance through adequate length.
Solution Approach 2:
The partition walls are designed with asymmetric lengths, where some partition walls extend further than others in the fluid flow direction. This asymmetric design creates variations in cell volume and flow paths, preventing uniform heat concentration and reducing super temperature rise at the outlet while preserving filtration performance.
3Reliability
If a depression is provided from the end face in the central portion to remove high temperature region, then thermal stress is reduced, but pressure loss decreases causing more gas flow and increased PM deposition in central portion leading to super temperature rise
Solution Approach 1:
Instead of creating a depression that alters overall flow distribution, the invention applies local quality variation through partition walls of different lengths in specific regions. This approach reduces thermal stress locally without creating the flow redistribution effect that would cause increased PM deposition and temperature rise in the central portion.
Solution Approach 2:
The invention extracts or removes the problematic depression structure from the design and replaces it with a different approach using varied partition wall lengths. This eliminates the unintended consequence of flow concentration in the central region while still addressing thermal stress reduction through localized structural variations.
4Quantity of substance
If a protrusion is provided from the end face in the central portion, then PM deposition region is extended, but heat from anterior increases causing super temperature rise on exhaust gas outlet side
Solution Approach 1:
The invention uses local quality variation through different partition wall lengths to extend PM deposition regions without creating the heat concentration problem. By strategically varying partition wall lengths in different areas, adequate PM deposition surface area is provided while preventing excessive heat generation that would lead to super temperature rise at the outlet.
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 effectively prevents thermal shock fractures and melting, maintains uniform pressure loss, and enhances exhaust gas purification performance by ensuring consistent heat transfer and distribution across the cells.
Implementation Method 1
since the bonding material layer functions as a cushion material for suppressing thermal expansion, the thermal stress is reduced
Implementation Method 2
the distance between a position having high temperature and a position having low temperature becomes short, and temperature gradient is small
Implementation Method 3
thermal shock fracture or melting of partition walls when it is used as a DPF. The thermal shock fracture or melting of partition walls is considered to be caused because temperature easily rises more on the exhaust gas outlet side
Data Source
Figure 1~3
Figure 4~7A
Figure 7B~8B
AI summary
There is provided a honeycomb structure having a plurality of honeycomb segments 2 having almost the same entire length and mutually having displacement in a fluid flow direction. The honeycomb structure is useful as a DPF, and it hardly has super temperature rise upon use or upon regeneration, thereby hardly causing melting or thermal shock fracture of partition walls.