Ammonia Diffuser Grid for SCR Catalyst Uniform Distribution
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Solution Overview
Problem
Current SCR catalyst systems for reducing nitrogen oxides in internal combustion engine exhaust gases face inefficiencies due to the lack of compactness, optimized diffusion of reducing agents, and significant pressure drops, leading to increased fuel consumption and delayed catalyst temperature reaching the optimal operating temperature.
Innovation Solution
A diffuser assembly integrated into the exhaust line, comprising a grid with a main distribution channel and secondary diffusion channels with orifices for ammonia distribution and heating elements, which combines the functions of a mixer and injector, ensuring uniform diffusion and heating of ammonia over the SCR catalyst surface, reducing pressure drops and facilitating compact installation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mixer is introduced to mix reducing agent with exhaust gases, then diffusion of reducing agent is improved, but pressure drop increases significantly
Solution Approach 1:
The diffuser is segmented into multiple secondary diffusion channels with orifices distributed across its surface, allowing the reducing agent to be introduced at multiple locations simultaneously. This segmentation enables effective diffusion without requiring a large-volume mixer, thereby reducing pressure drop while maintaining mixing effectiveness.
Solution Approach 2:
The diffuser utilizes a porous grid structure with numerous orifices that allow the reducing agent to diffuse through the exhaust gas flow. This porous approach enables efficient mass transfer without creating significant flow resistance, solving the contradiction between diffusion effectiveness and pressure drop.
2Reliability
If mixer thickness is increased to include impactors, then diffusion of reducing agent is improved, but compactness is reduced
Solution Approach 1:
Instead of increasing thickness in the axial direction, the diffuser distributes orifices across the radial surface area of the exhaust line. This dimensional shift from axial to radial distribution allows effective diffusion within a compact thickness, maintaining compactness while improving diffusion.
Solution Approach 2:
The diffuser grid is nested within the exhaust line geometry, conforming to the inner wall profile. This nesting allows the diffuser to be integrated into the existing exhaust line volume without requiring additional axial space, maintaining compactness while providing effective diffusion through the distributed orifices.
3Temperature
If heating grid is separated from mixer, then heating function is improved, but axial size increases
Solution Approach 1:
The heating function is merged with the diffuser structure by integrating heating elements directly into the secondary diffusion channels. This combination eliminates the need for a separate heating grid, reducing axial size while maintaining effective heating of the reducing agent and exhaust gas mixture.
Solution Approach 2:
The diffuser structure serves multiple functions simultaneously: it distributes the reducing agent through distributed orifices, heats the mixture through integrated heating elements, and maintains compact geometry. This multi-functionality eliminates the need for separate components, reducing overall axial size while improving heating efficiency.
4Reliability
If reducing agent is introduced well upstream to homogenize mixture, then diffusion is improved, but system complexity increases
Solution Approach 1:
The diffuser performs preliminary mixing action at the point of injection by distributing the reducing agent through multiple orifices across the exhaust line cross-section. This preliminary homogenization occurs immediately upon introduction, eliminating the need for extended mixing sections or complex downstream mixing 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 diffuser assembly enhances the efficiency of nitrogen oxide treatment by ensuring uniform ammonia distribution and reduced pressure drops, leading to lower fuel consumption and faster catalyst temperature achievement, thus improving the overall SCR catalyst performance.
Implementation Method 1
one or more heating means arranged inside the secondary diffusion channels adapted to heat an exhaust gas flowing in said pipe
Implementation Method 2
a diffuser for diffusing a gas to be diffused in a pipe, for example ammonia, said diffuser being in the form of a grid adapted to conform to the inner wall of the pipe
Data Source
Figure 1~2
Figure 3
AI summary
The present invention relates to a diffuser (220) for diffusing a gas in a pipe, the diffuser (220) being in the form of a grid adapted to conform to the inner wall of the pipe, which may, for example, be an exhaust line (30) connected to an internal combustion engine through which exhaust gases flow. The present invention also relates to an assembly (20) for reducing nitrogen oxides flowing in the exhaust line (30) of an internal combustion engine, comprising the diffuser (220) and a catalyst (10) for the selective reduction of nitrogen oxides contained in the exhaust gases, the catalyst (10) being disposed downstream of the diffuser (220).