Honeycomb Structure with Curved Intersections for Diesel Exhaust
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Solution Overview
Problem
Honeycomb structures face a challenge in simultaneously achieving high temperature rise performance and high thermal capacity, which is essential for efficient particulate matter regeneration and exhaust gas purification in diesel engines, as they often require a catalyst activation temperature that is difficult to maintain due to low exhaust temperatures.
Innovation Solution
The honeycomb structure is designed with partition walls made of ceramics like cordierite, alumina, or lithium aluminosilicate, featuring a curved intersection shape and a specific diagonal-to-thickness ratio (L/T ≥ 1.6) to enhance temperature rise performance while maintaining sufficient thermal capacity, and is optionally coated with catalysts like oxidation or NOx reduction catalysts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the thermal capacity of the substrate is reduced to improve temperature rise characteristic, then the catalyst activation temperature is quickly reached, but when exhaust gas temperature drops, the temperature rapidly drops below the catalyst activation temperature
Solution Approach 1:
The partition walls are designed with non-uniform thickness, featuring a first thickness in a first region and a second thickness in a second region. This local variation in thickness allows different regions to serve different functions: thinner regions facilitate faster temperature rise, while thicker regions provide thermal capacity to maintain temperature stability, thereby resolving the contradiction between quick catalyst activation and temperature maintenance.
2Temperature
If the partition wall thickness is increased to increase thermal capacity, then temperature stability is improved, but the temperature rise characteristic deteriorates and catalyst activation is delayed
Solution Approach 1:
The partition walls are designed with non-uniform thickness, featuring a first thickness in a first region and a second thickness in a second region. This local variation in thickness allows different regions to serve different functions: thinner regions facilitate faster temperature rise, while thicker regions provide thermal capacity to maintain temperature stability, thereby resolving the contradiction between quick catalyst activation and temperature maintenance.
3Speed
If the porosity is increased to reduce thermal capacity, then temperature rise characteristic is improved, but thermal capacity is insufficient to maintain catalyst activation temperature
Solution Approach 1:
The partition walls are designed with non-uniform thickness, featuring a first thickness in a first region and a second thickness in a second region. This local variation in thickness allows different regions to serve different functions: thinner regions facilitate faster temperature rise, while thicker regions provide thermal capacity to maintain temperature stability, thereby resolving the contradiction between quick catalyst activation and temperature maintenance.
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
This design allows for improved temperature rise performance and prolonged catalyst activation time, ensuring efficient particulate matter regeneration and exhaust gas purification, even at low exhaust temperatures, while minimizing pressure losses and maintaining uniform temperature distribution.
Implementation Method 1
the thermal capacity of the substrate is increased. In this case, the temperature rise characteristic deteriorates, and there is an antinomic relation between the thermal capacity and the temperature rise characteristic
Implementation Method 2
a method is adopted in which the DPF is coated with a catalyst that oxidizes the PM
Implementation Method 3
the temperature of the honeycomb structure rapidly drops below the catalyst activation temperature
Data Source
Figure 1~3
AI summary
There is disclosed a honeycomb structure which solves a problem of antinomy that it is difficult to satisfy both of a high temperature rise performance and a high thermal capacity at the same time and which is disposed at a previous stage of a filter for trapping particulate matters (PM) discharged from a diesel engine so that regeneration of the PM trapped by the filter can smoothly be completed and an exhaust gas can efficiently be purified. In a honeycomb structure in which a plurality of cells arranged in parallel with one another to communicate between two end surfaces of the honeycomb structure are formed by a plurality of partition walls, the plurality of partition walls are made of a ceramic, each cell is formed into a substantially square shape, an intersection between the partition walls is formed into an R-shape or a C-shape, a value (L/T) of a ratio of a diagonal distance L between the intersections to an average thickness T of the partition walls is set to 1.6 or more, and an open area ratio of the cells is set to 55% or more.