Catalyst Support Offset Structure Wind Erosion Protection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Catalyst carriers with an offset structure suffer from wind erosion on all end surfaces when used in exhaust gas purification systems, leading to premature deterioration, whereas those without an offset structure experience wind erosion only at the inlet side, resulting in reduced catalyst effectiveness and durability issues.
Innovation Solution
A metal substrate for catalytic converters is developed with a honeycomb structure featuring a corrugated and flat stainless foil configuration, where an oxide film containing 30% or more α-alumina is formed on the end surfaces of the fins to protect against wind erosion, enhancing the catalyst carrier's durability and purification performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a catalyst carrier with an offset structure is used to increase catalyst surface area, then purification performance is improved, but wind erosion occurs on all fin end surfaces leading to premature deterioration
Solution Approach 1:
The invention applies a protective oxide film containing 30% or more α-alumina specifically to the end surfaces of fins that are exposed to the gas inlet side. This local treatment provides erosion resistance precisely where wind erosion occurs most severely, while maintaining the offset structure's purification performance benefits throughout the catalyst carrier.
2Productivity
If the offset structure is used to enhance catalyst effectiveness, then purification efficiency increases, but catalyst peeling and wind erosion expand from lost parts
Solution Approach 1:
The protective oxide film is formed on the fin end surfaces before the catalyst carrier is put into service. This preliminary protective layer prevents catalyst peeling and wind erosion from initiating at the vulnerable fin ends, thereby preventing the expansion of erosion regions that would otherwise occur during operation.
Solution Approach 2:
The invention creates a composite structure where a protective oxide film containing α-alumina is formed on the metal substrate surface. This composite material combination provides both the structural integrity of the metal substrate and the erosion resistance of the alumina oxide film, preventing catalyst peeling while maintaining purification efficiency.
3Temperature
If stainless foil is used as metal substrate for high-temperature oxidation resistance, then thermal stability is improved, but wind erosion still occurs on fin end surfaces
Solution Approach 1:
The invention applies a specialized protective oxide film containing 30% or more α-alumina specifically to the fin end surfaces exposed to gas inlet, while the bulk stainless foil maintains its high-temperature oxidation resistance. This local enhancement addresses wind erosion at vulnerable points without compromising the overall thermal stability of the substrate.
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 oxide film effectively protects the end surfaces of the catalyst carrier from wind erosion, maintaining the catalyst's effectiveness and extending its lifespan, while ensuring high-temperature oxidation resistance and improved mechanical strength.
Implementation Method 1
an end surface on a gas inlet side of each fin was lost. Exhaust gas flowing into DOC contains PM. Therefore, it is considered that when the exhaust gas containing the PM collides with the end surface on the gas inlet side of each fin, the catalyst is decreased or peeled
Implementation Method 2
a catalyst layer is formed on a metal honeycomb metal substrate that is obtained by working a stainless foil... excellent high-temperature oxidation resistance
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
[Problem] To protect the gas-inlet-side edge surfaces of a catalyst support having an offset structure from wind erosion. [Solution] A base for supporting a catalyst for exhaust gas purification, the base including a honeycomb structure obtained by superposing a metallic flat foil and a metallic wavy foil, characterized in that the wavy foil has offset portions where any adjoining two of the wave phases arranged in the axial direction of the honeycomb structure are offset from each other. The base is further characterized in that an oxide coating film has been formed in a given range of these offset portions which includes exposed edge surfaces that are exposed on the gas-inlet side, that the oxide coating film includes 30-99.9 mass% first alumina, with the remainder comprising at least one of second aluminas, Fe oxides, and Cr oxides, that the first alumina comprises α-alumina, that the second aluminas comprise one or more of γ-, θ-, χ-, δ-, η-, and κ-aluminas, and that the given range extends from the exposed edge surfaces to a distance of at least 2 mm therefrom along the gas flow direction.