SiC Honeycomb Filter Managing Heat Stress
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Solution Overview
Problem
Current diesel engine filters face challenges in preventing damage from heat stress during recovery treatments without increasing pressure loss or deteriorating particulate matter (PM) collecting efficiency, as existing methods either fail to adequately manage thermal expansion or lead to clogged pores and reduced efficiency.
Innovation Solution
A fine particle collecting filter with a honeycomb structure made from silicon carbide, featuring specific pore diameters, thermal conductivity, porosity, and cell density to effectively manage heat stress and maintain PM collecting efficiency, using a joining material with inorganic particles and colloidal oxide for integration of honeycomb segments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the honeycomb structure is manufactured as one piece, then the structure is simple and strong, but the heat stress during recovery causes damage to the filter
Solution Approach 1:
The honeycomb structure is divided into multiple segments that are joined together using a joining material. This segmentation allows the structure to flex and accommodate thermal expansion during recovery, preventing damage while maintaining overall structural integrity. The joining material acts as a buffer that absorbs thermal stress between segments.
2Temperature
If a material with large heat capacity is used to suppress temperature rise, then the heat stress is reduced, but the thermal expansion coefficient is excessively large causing heat stress cracks
Solution Approach 1:
The invention optimizes the pore size parameters of the partition walls to balance heat capacity and thermal expansion. By controlling the pore diameter within a specific range, the material achieves sufficient heat capacity to suppress temperature rise while maintaining an appropriate thermal expansion coefficient to prevent cracks.
3Temperature
If the porosity of the material is lowered to increase heat capacity, then the temperature rise is suppressed, but the pores are easily clogged with PM and pressure loss increases
Solution Approach 1:
The invention precisely controls the pore diameter parameter within the range of 0.03 to 10 μm to achieve optimal balance. This parameter optimization ensures sufficient porosity to prevent PM clogging and maintain low pressure loss, while simultaneously providing adequate heat capacity to suppress temperature rise during recovery.
4Productivity
If the pore diameter is reduced to improve PM collecting efficiency, then the PM collection is enhanced, but the pressure loss increases
Solution Approach 1:
The invention optimizes the pore diameter parameter within the specific range of 0.03 to 10 μm to achieve the best balance between PM collecting efficiency and pressure loss. This parameter control ensures that pores are small enough to capture fine PM particles while remaining large enough to prevent excessive pressure loss.
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
The filter effectively alleviates heat stress damage, maintains PM collecting efficiency, and prevents excessive pressure loss by optimizing thermal conductivity and porosity within the honeycomb structure, ensuring durability and performance.
Implementation Method 1
a thermal conductivity of the partition walls at room temperature is from 80 to 110 W/mK
Implementation Method 2
a low temperature portion is pulled due to thermal expansion of a high temperature portion in which the excessively large temperature rise has occurred
Data Source
Figure 1~2
Figure 3~4
AI summary
There is disclosed a fine particle collecting filter which enables effectively preventing damage due to a heat stress generated during recovery, without incurring increase of a pressure loss or deterioration of a PM collecting efficiency. A fine particle collecting filter 1 includes a honeycomb structure 2 in which a plurality of honeycomb segments 3 are integrally joined by a joining material 12, and has a constitution where an exhaust gas allowed to flow from an inlet end surface into cells 7 passes partition walls 8, and then flows out from an outlet end surface to the outsides of the cells 7. The partition walls 8 are made of a material containing SiC as a main component, at least one of an average open diameter of pores which are open in a surface of each of the partition walls 8 that becomes an inlet side of the exhaust gas passing the partition wall 8 and an average open diameter of the pores which are open in a surface of the partition wall 8 that becomes an outlet side of the exhaust gas passing the partition wall 8 is from 0.1 to 5 µm, an average pore diameter of the whole partition wall 8 is from 10 to 30 µm, and a thermal conductivity of the partition walls 8 at room temperature is from 80 to 110 W/mK.