Gradient Ceramic Substrate for Fast Catalyst Light Off
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Solution Overview
Problem
Ceramic honeycomb substrates used in vehicular exhaust systems face challenges with long light off times, mechanical weakness, and erosion resistance, particularly with thin-walled or high-porosity designs, which compromise their effectiveness and durability.
Innovation Solution
A catalytic flow-through ceramic substrate with varying wall thickness and porosity along its axis, featuring a thinner, more porous region near the inlet end and a thicker, less porous region elsewhere, along with radial thickening, to reduce light off time without sacrificing mechanical strength and enhance erosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If thin-walled ceramic substrates are used to reduce light off time, then light off time is reduced, but mechanical strength deteriorates
Solution Approach 1:
The patent applies local quality by creating a gradient in wall thickness along the axial direction of the ceramic substrate. The inlet end features thinner walls to reduce thermal mass and light off time, while the outlet end maintains thicker walls to preserve mechanical strength and erosion resistance. This spatial variation in geometric properties allows simultaneous optimization of both light off time and mechanical strength.
2Loss of time
If thin-walled ceramic substrates are used to reduce light off time, then light off time is reduced, but erosion resistance deteriorates
Solution Approach 1:
The patent implements local quality through axial variation in wall thickness, making the inlet end thinner for reduced light off time while maintaining thicker walls at the outlet end that are more resistant to erosion from exhaust gas particulates. This spatial differentiation allows the substrate to achieve both fast light off characteristics and adequate erosion resistance.
3Loss of time
If high-porosity substrates are used to reduce light off time, then light off time is reduced, but mechanical strength deteriorates
Solution Approach 1:
The patent applies local quality by varying wall thickness along the axial direction rather than uniformly increasing porosity throughout the entire substrate. The inlet end has thinner walls that effectively reduce thermal mass and light off time, while the outlet end maintains sufficient wall thickness to preserve mechanical strength, avoiding the weaknesses of uniformly high-porosity designs.
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 solution achieves a 10-25% reduction in light off time while maintaining or improving mechanical strength and durability, and reducing thermal stresses that can lead to cracking, with minimal impact on manufacturing complexity or cost.
Implementation Method 1
the time it takes before the webs reach the required 250° C. before the catalyst impregnated over the walls begins to oxidize CO to CO2
Implementation Method 2
the catalyst impregnated over the walls begins to oxidize CO to CO2
Implementation Method 3
to effectively disassociate NOx into N2 and O2
Data Source
AI summary
A fast light off flow-through ceramic substrate is provided that is particularly adapted for use as a catalytic converter. The substrate is formed from a body of ceramic material having axially opposing inlet and outlet ends for receiving and expelling the flow of automotive exhaust gas, respectively. The body contains a network of walls coated with a catalyst that define axially-oriented flow-through cell channels. The average thermal mass (ATM1) of a first axial region of the walls adjacent to the inlet end is at least 20% less than the average thermal mass (ATMTOT) of all of the walls. The lower average thermal mass of the walls in the first region advantageously shortens the light off time for the catalyst within the substrate to effectively neutralize automotive pollutants. The reduction of the average thermal mass in only the first axial region of the walls advantageously maintains the strength of the resulting body of ceramic material, and further increases the cool down time of the body.