Flow Reversal Decomposition Chamber for SCR Residence Time
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Solution Overview
Problem
Existing catalytic reduction systems for internal combustion engine exhausts face challenges in ensuring adequate residence time for reducing agents like urea to decompose into ammonia, which is crucial for effective NOx reduction, as improper decomposition leads to inefficient SCR system operation.
Innovation Solution
The design of a decomposition chamber with annulated flow reversal chambers that increase the residence time of the reducing agent by folding the exhaust flow back on itself, allowing a longer effective path length without increasing the overall chamber length, and utilizing a helical flow pattern with fins to enhance decomposition and reduce backpressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If the chamber length is increased to provide adequate residence time for urea decomposition, then the decomposition efficiency is improved, but the overall system size and complexity increase
Solution Approach 1:
The chamber is divided into multiple flow reversal sections with internal partitions that create alternating flow directions. This segmentation allows the exhaust gas to traverse a longer effective path within a compact physical footprint, increasing residence time without proportionally increasing chamber length.
Solution Approach 2:
The patent introduces flow reversal in the axial dimension by creating alternating forward and backward flow sections. This dimensional approach to flow management enables the gas to cover a longer distance (increasing residence time) while maintaining a compact chamber length by utilizing back-and-forth motion rather than simple linear extension.
2Reliability
If the chamber length is increased to ensure complete urea decomposition, then the SCR system efficiency is improved, but the device complexity and space requirements increase
Solution Approach 1:
The chamber is divided into multiple flow reversal sections with internal partitions that create alternating flow directions. This segmentation allows the exhaust gas to traverse a longer effective path within a compact physical footprint, increasing residence time without proportionally increasing chamber length.
Solution Approach 2:
Instead of allowing continuous forward flow, the patent inverts the flow direction periodically through internal partitions. This inversion creates multiple passes through the chamber, ensuring complete decomposition of urea while maintaining a compact structure that does not require simple linear length extension.
3Length of stationary object
If a straight through flow path is used, then the chamber length can be reduced, but the residence time is insufficient for complete decomposition
Solution Approach 1:
The patent introduces flow reversal in the axial dimension by creating alternating forward and backward flow sections. This dimensional approach to flow management enables the gas to cover a longer distance (increasing residence time) while maintaining a compact chamber length by utilizing back-and-forth motion rather than simple linear extension.
Solution Approach 2:
The chamber is divided into multiple flow reversal sections with internal partitions that create alternating flow directions. This segmentation allows the exhaust gas to traverse a longer effective path within a compact physical footprint, increasing residence time without proportionally increasing chamber length.
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 configuration ensures complete decomposition of urea into ammonia, enhancing the efficiency of the SCR system by increasing the residence time of the reducing agent, reducing the need for insulation due to retained heat, and minimizing the overall length of the decomposition chamber.
Implementation Method 1
decomposition chamber with annulated flow reversal chambers for increased residence time... folding the exhaust flow back on itself
Implementation Method 2
urea behind, which decomposes and hydrolyzes into ammonia. Ammonia is thus produced through the evaporation of the water droplets and urea decomposition
Implementation Method 3
Water in the droplets from the injection solution evaporates, leaving urea behind
Implementation Method 4
utilizing a helical flow pattern with fins to enhance decomposition and reduce backpressure
Implementation Method 5
NOx reacts with the ammonia and is catalytically reduced in the presence of ammonia
Data Source
AI summary
An apparatus is disclosed for increasing the residency time of a reducing agent in an exhaust gas cleaning system. The apparatus includes a first double-walled element in communication with a flow of exhaust having a first inner wall and a first outer wall. A second double-walled element is included having a second inner wall and a second outer wall. The second double-walled element is arranged in relation to the first double-walled element such that the second inner wall is positioned between the first inner wall and the first outer wall and the first outer wall is positioned between the second inner wall and the second outer wall. This arrangement defines a plurality of flow paths that reverses the flow of exhaust back on itself and then reverses the flow of exhaust once again.