Diesel Particulate Filter Coating for Back Pressure Control
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Solution Overview
Problem
Diesel particulate filters with ceramic wall-flow substrates experience a sudden increase in dynamic pressure due to depth filtration, leading to reduced engine power and increased fuel consumption, as the pore diameter reduction causes filter cake formation and linear back pressure increase.
Innovation Solution
Applying a high-melting oxide coating in the inflow channels of the wall-flow filter substrate, with a particle size distribution matched to the pore sizes, to reduce depth filtration and minimize back pressure rise, using a process involving suspension, grinding, filling, drying, and calcination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ceramic wall-flow filter substrate is used for high filtration efficiency, then soot particles are effectively removed, but the pore diameter reduces rapidly during depth filtration causing sudden back pressure increase
Solution Approach 1:
The patent applies a coating layer to the inflow channels before the filtration process begins. This preliminary action creates a controlled filtration mechanism that prevents the rapid pore diameter reduction and sudden back pressure increase that occurs in uncoated substrates during depth filtration.
Solution Approach 2:
The patent uses a porous coating layer made of high-melting-point oxide particles with specific size distribution (d50 between 10-15 μm, d90 between 25-40 μm) that matches the substrate pore structure. This porous structure allows gradual soot particle capture while maintaining stable gas flow and preventing rapid back pressure increase.
2Reliability
If the pore radius narrows rapidly during depth filtration to improve soot particle capture, then filtration efficiency increases, but engine power is reduced due to higher back pressure
Solution Approach 1:
The coating layer is applied in advance to create a controlled filtration mechanism that prevents rapid pore narrowing. This preliminary structure allows soot particles to be captured gradually without causing sudden back pressure increases that would reduce engine power.
Solution Approach 2:
The patent changes the particle size parameters of the coating material (d50: 10-15 μm, d90: 25-40 μm) to match the substrate pore size distribution. This parameter optimization ensures gradual pore filling that maintains stable pressure characteristics while achieving effective soot filtration.
3Power
If a coating is applied to reduce back pressure increase, then engine power utilization improves, but the initial back pressure in soot-free state increases
Solution Approach 1:
The patent optimizes the particle size distribution parameters of the coating material (d50 between 10-15 μm, d90 between 25-40 μm) to balance the initial back pressure increase with the reduction in back pressure increase rate during operation. This parameter optimization ensures the coating provides the desired back pressure stabilization while minimizing initial resistance.
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
Significantly reduces the increase in back pressure during the depth filtration phase, maintaining filtration efficiency and catalytic properties, thereby optimizing engine power utilization and reducing fuel consumption.
Implementation Method 1
the coating being designed to seal the pores in the wall connecting the inflow and outflow channels on the upstream side for soot particles without preventing the passage of gaseous exhaust gas components
Implementation Method 2
Milling the aqueous suspension obtained in step a. until the oxide has a particle size distribution adapted to the pore size distribution in the wall of the wall-flow filter substrate
Implementation Method 3
Drying the wall-flow filter substrate resulting from step d. in a hot air stream at 80 to 180°C
Implementation Method 4
Calcining the wall-flow filter substrate resulting from step e. at 250 to 600°C
Data Source
Figure 1a~1b
Figure 2a~2c
Figure 3~4
AI summary
The filter has flow channels (1) provided with a coating (6) made of high-melting material. The coating closes pores (5) for soot particles (7) in a wall (4) of a ceramic wall flow filter substrate without penetration of gaseous exhaust gas components. The pores connect flow channels and disperse channels (2) with each other. Particle sizes of the material are adapted to sizes of the pores such that a value of particle sizes distribution of the material is equal to or larger than a value of pores sizes distribution of the substrate. The coating includes a thickness of 10 to 150 micrometers.