Dry Powder Coating Filter Diffuser Divergent Inlet Passage
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Solution Overview
Problem
Ceramic wall-flow filters used in emissions control for internal combustion engines face challenges in maintaining filtration efficiency, especially during the early life of the filter, regeneration, and when loaded with soot, due to particulate matter accumulation, which leads to decreased performance and increased back pressure.
Innovation Solution
A dry powder coating method using a filter holder with an inlet passage featuring a diffuser and divergent portion to improve powder distribution across the filter's porous structure, ensuring even adhesion and resistance to de-adhesion without the need for binders or high-temperature sintering, utilizing refractory powders or metal compounds that decompose into oxides for enhanced durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If dry powder is sprayed onto the filter without a diffuser and divergent portion, then the coating process is simpler, but the powder distribution across the filter surface is uneven
Solution Approach 1:
A diffuser is introduced as an intermediary component in the inlet passage to mediate between the powder spray source and the filter surface. The diffuser disperses the powder-gas mixture uniformly across the inlet face of the filter, ensuring even powder distribution without requiring complex multi-nozzle systems
Solution Approach 2:
The inlet passage is segmented into distinct functional zones: a convergent portion that directs the flow, a diffuser section that disperses the powder-gas mixture, and a divergent portion that expands the flow area. This segmentation allows each section to optimize its function for achieving uniform powder distribution
2Reliability
If binder materials are used to enhance powder adhesion, then coating durability improves, but contamination of exhaust gas increases and filtration performance deteriorates
Solution Approach 1:
The filter structure itself provides the adhesion mechanism through its porous surface characteristics. The dry powder penetrates and adheres to the porous structure through physical interlocking and surface forces, eliminating the need for external binder materials that would contaminate exhaust gas
Solution Approach 2:
The porous nature of the filter substrate is utilized to enhance powder adhesion. The powder particles penetrate into the porous structure and anchor themselves through capillary forces and physical interlocking, achieving durable adhesion without requiring additional binder materials
3Strength
If high-temperature sintering is applied to bond the powder coating, then coating strength improves, but the filter structure may be damaged and manufacturing complexity increases
Solution Approach 1:
The mechanical/thermal bonding process (sintering) is replaced with a chemical/adhesive bonding mechanism. Powder particles containing reactive metal compounds form strong bonds with the ceramic filter surface through chemical reactions at lower temperatures, eliminating the need for high-temperature sintering equipment and complex manufacturing processes
4Reliability
If the filter operates without powder coating, then back pressure remains low initially, but filtration efficiency decreases during early life and regeneration periods
Solution Approach 1:
The filter surface is pre-coated with dry powder before the filter enters service. This preliminary action ensures that the filter maintains consistent high filtration efficiency from the beginning of its operational life, during regeneration cycles, and under various loading conditions, eliminating the need for complex real-time adjustment systems
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 method achieves improved filtration efficiency and durability by ensuring uniform powder distribution and adhesion to the filter, maintaining performance across various operational conditions and reducing back pressure.
Implementation Method 1
establishing a primary gas flow through the porous structure of the filter by applying a pressure reduction to the outlet face of the filter
Implementation Method 2
transferring the dry powder from the reservoir to a spray device located upstream of the inlet face of the filter; spraying the dry powder, using the spray device, towards the inlet face of the filter such that the dry powder is entrained in the primary gas flow
Implementation Method 3
The inlet passage may comprise a diffuser and a divergent portion, downstream of the diffuser, that is outwardly tapered, or otherwise increases in its area for flow, towards the inlet face of the filter
Implementation Method 4
the dry powder comprises or consists of a metal compound for forming by thermal decomposition a metal oxide
Data Source
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AI summary
An apparatus (1) for dry powder coating a filter (2), comprising: i) a filter holder for holding a filter; ii) an inlet passage (5) for receiving a mixture of dry powder and gas, the inlet passage (5) communicating in use with an inlet face (3) of the filter (2) held by the filter holder; and iii) an outlet passage (6) comprising a first end (31) communicating in use with an outlet face (4) of the filter (2) held by the filter holder and a second end (32) communicating with a vacuum generator (9). The inlet passage (5) comprises a diffuser (21), and a divergent portion (22), downstream of the diffuser (21), that is outwardly tapered, or otherwise increases in its area for flow, towards the inlet face (3) of the filter (2).