Decomposition Pipe Mixing Member Reductant Deposit Reduction
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Solution Overview
Problem
Current aftertreatment systems for internal combustion engines face issues with reductant material deposits in decomposition pipes, leading to reduced SCR efficiency, increased exhaust restriction, and excess ammonia concentration due to incomplete urea decomposition at specific temperature ranges.
Innovation Solution
The system incorporates a decomposition pipe with a flow restriction portion and a mixing member, where the reductant injector provides a spray that impinges on the mixing member, increasing exhaust velocity and turbulence, thereby preventing deposits by ensuring complete decomposition of urea before the exhaust reaches the NOx reduction catalyst.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If urea is injected into the exhaust stream for SCR, then NOx removal is achieved, but reductant material deposits form on decomposition pipe surfaces
Solution Approach 1:
The patent applies preliminary action by ensuring complete urea decomposition occurs in the decomposition pipe before the exhaust reaches the NOx reduction catalyst. The flow restriction portion creates conditions (increased velocity, turbulence, extended residence time) that guarantee full decomposition of urea into ammonia and gaseous products, preventing any undecomposed urea from depositing on downstream surfaces.
Solution Approach 2:
The patent changes key parameters in the decomposition pipe: introducing a flow restriction portion that increases exhaust gas velocity, creating turbulence to enhance heat and mass transfer, and extending the residence time. These parameter changes ensure complete urea decomposition while preventing deposit formation on pipe surfaces.
2Reliability
If decomposition pipe length is increased to provide residence time, then urea decomposition is improved, but exhaust restriction increases
Solution Approach 1:
The patent applies local quality by placing a flow restriction portion at a specific location within the decomposition pipe. This localized restriction creates high velocity and turbulence only in the critical decomposition zone, providing sufficient residence time for complete urea decomposition without requiring the entire pipe to be lengthy, thus minimizing overall exhaust restriction.
Solution Approach 2:
The flow restriction portion is positioned upstream of the NOx reduction catalyst to ensure complete urea decomposition occurs before the exhaust enters the catalyst. This preliminary action prevents undecomposed urea from reaching the catalyst, eliminating the need for excessively long pipe lengths.
3Reliability
If reductant spray is injected to improve dispersion, then SCR efficiency is enhanced, but deposit formation on mixing member surfaces increases
Solution Approach 1:
The patent ensures complete urea decomposition occurs in the decomposition pipe before the exhaust reaches the NOx reduction catalyst. The flow restriction portion creates conditions (high velocity, turbulence, extended residence time) that guarantee full decomposition of urea into ammonia and gaseous products, preventing any undecomposed urea from depositing on downstream surfaces including the mixing member.
Solution Approach 2:
The flow restriction portion changes the flow parameters by increasing velocity and creating turbulence, which enhances heat and mass transfer. These parameter changes ensure complete urea decomposition while preventing deposit formation on the mixing member and other pipe surfaces.
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 reduces the likelihood of reductant deposits on internal surfaces, enhances reductant dispersion, and maintains efficient SCR operation by ensuring complete urea decomposition, thus preventing exhaust restriction and ammonia excess.
Implementation Method 1
heat from the exhaust gas evaporates water from the urea and provides the activation energy needed to chemically decompose the urea
Implementation Method 2
heat from the exhaust gas evaporates water from the urea and provides the activation energy needed to chemically decompose the urea
Implementation Method 3
a mixing device to improve the uniformity of the reductant dispersion in the exhaust gas
Data Source
AI summary
In one non-limiting embodiment, an apparatus for treating exhaust includes a reductant injector, an aftertreatment component including a NOx reduction catalyst, and a pathway for directing exhaust to the aftertreatment component. The pathway includes a constriction zone within which is positioned a mixing member. The constriction zone begins downstream of the reductant injector and upstream from the aftertreatment component. However, other embodiments, forms and applications are also envisioned.