SiC-Si Filter with Graded Pores for Heat Stress Resistance
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Solution Overview
Problem
Current diesel engine particulate filters face challenges in withstanding heat stress during recovery treatments, leading to potential damage such as cracks, while maintaining high PM collecting efficiency and low pressure loss, due to limitations in thermal expansion, porosity, and pore size.
Innovation Solution
A fine particle collecting filter with a honeycomb structure where SiC aggregate is bound by Si, featuring specific pore diameters, thermal conductivity, porosity, and cell density ranges to alleviate heat stress without increasing pressure loss or deteriorating PM collecting efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the filter uses a honeycomb structure with high porosity to maintain low pressure loss, then the PM collecting efficiency is preserved, but the heat stress resistance during recovery treatment deteriorates
Solution Approach 1:
The invention optimizes specific parameters of the honeycomb structure including porosity (40-50%), cell density (200-400 cells/inch²), and wall thickness (0.5-1.5mm) to achieve a balance between pressure loss and heat stress resistance. By precisely controlling these parameters, the filter maintains adequate porosity for low pressure loss while ensuring sufficient structural integrity to withstand thermal expansion during recovery treatment.
Solution Approach 2:
The invention employs composite material composition for the honeycomb walls, utilizing materials with appropriate thermal conductivity (1-5 W/mK) and mechanical strength. The composite structure combines materials that provide both thermal insulation to reduce heat stress and sufficient strength to prevent cracking during thermal cycling, while maintaining the porous structure needed for gas flow.
2Reliability
If the filter structure is made more robust to withstand heat stress during recovery, then the heat stress resistance is improved, but the pressure loss increases and PM collecting efficiency deteriorates
Solution Approach 1:
The invention establishes optimal parameter ranges where wall thickness is controlled at 0.5-1.5mm (not excessively thick), porosity at 40-50% (maintaining adequate open space), and cell density at 200-400 cells/inch². These parameter optimizations ensure the structure is robust enough for heat stress resistance while maintaining sufficient porosity to prevent excessive pressure loss and preserve PM collecting efficiency.
3Reliability
If the pore size is reduced to improve PM collecting efficiency, then the PM collection capability increases, but the pressure loss increases
Solution Approach 1:
The invention optimizes the pore size distribution and porosity to fall within the 40-50% range, with cell density controlled at 200-400 cells/inch². This parameter optimization creates a balance where pores are sufficiently small to capture fine PM particles effectively, while the overall porosity remains high enough to allow adequate gas flow and 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 prevents damage from heat stress during recovery treatments while maintaining high PM collecting efficiency and low pressure loss, as demonstrated by the specified parameters of pore diameters, thermal conductivity, and cell density.
Implementation Method 1
When the exhaust gas passes the partition walls, the partition walls function as filter layers, so that the PM included in the exhaust gas is collected
Implementation Method 2
it is necessary to remove the PM deposited in the filter by burning the PM with a high temperature gas
Implementation Method 3
a thermal conductivity of the partition walls at room temperature is from 50 to 80 W/mK
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. In the partition walls 8, SiC which is an aggregate is bound by Si which is a binding agent, at least one of an average open diameter of the 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 50 to 80 W/mK.