Angled Exhaust Dosing Module for SCR Urea Decomposition
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Solution Overview
Problem
Existing methods for dosing urea-based reducing agents into combustion engine exhaust streams for SCR and SCRT systems suffer from incomplete decomposition and non-uniform mixing, leading to reduced catalyst efficiency and the formation of reactive deposits due to strong spray-wall interactions.
Innovation Solution
A method involving a dosing module with an annular inlet jet inclined to the longitudinal axis and a coaxial urea-based reducing agent spray, generating turbulence for complete decomposition and preventing spray droplets from hitting the sidewalls, thereby ensuring uniform mixing and avoiding deposits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the exhaust gas stream is axially introduced inside the dosing module housing with a centrally placed injector, then the structure is simple, but the spray droplets hit the sidewalls causing liquid deposits and incomplete decomposition
Solution Approach 1:
The patent introduces the exhaust gas stream at an angle relative to the longitudinal axis of the dosing module housing, creating an asymmetric flow pattern. This angled introduction causes the exhaust gas to flow along one side of the housing rather than axially down the center, preventing spray droplets from hitting the sidewalls and forming liquid deposits.
Solution Approach 2:
The patent changes the flow direction from a one-dimensional axial flow to a two-dimensional diagonal flow by introducing the exhaust gas at an angle. This dimensional change redirects the spray trajectory away from the sidewalls while maintaining complete decomposition of urea through increased turbulence and mixing path length.
2Stability of the object's composition
If the injector is placed on the centerline of the dosing module housing, then the spray distribution is symmetric, but the mixing of ammonia with exhaust gas is non-uniform reducing catalyst efficiency
Solution Approach 1:
The patent positions the injector off-center and introduces exhaust gas at an angle, creating an asymmetric spray pattern. This asymmetry ensures that the spray cloud is carried by the exhaust flow along the housing wall, improving contact between ammonia and exhaust gas for more uniform mixing and higher catalyst efficiency.
Solution Approach 2:
The patent creates different flow conditions in different regions of the dosing module. The angled exhaust introduction creates high-velocity turbulent flow in the region where spray is introduced, enhancing local mixing quality. The spray cloud is concentrated in specific zones where it can decompose completely and mix uniformly before reaching the catalyst.
3Speed
If the exhaust gas stream velocity is high, then the spray is carried away from sidewalls preventing deposits, but the decomposition of urea becomes incomplete
Solution Approach 1:
The patent introduces exhaust gas at an angle rather than axially, creating a diagonal flow path. This dimensional change extends the residence time of spray droplets in the hot exhaust gas by increasing the path length, allowing complete decomposition even at high velocities. The angled introduction also creates rotational flow patterns that enhance mixing.
Solution Approach 2:
The patent creates dynamic turbulent flow conditions through angled exhaust introduction. The oblique flow generates eddies and recirculation zones that continuously mix the spray cloud with exhaust gas, maintaining decomposition efficiency even at high gas velocities. The turbulent flow ensures that spray droplets remain suspended in the reaction zone longer.
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 method achieves complete urea decomposition and uniform ammonia mixing with exhaust gases, enhancing catalyst efficiency while preventing liquid deposits on exhaust system surfaces.
Implementation Method 1
generating turbulence for complete decomposition and preventing spray droplets from hitting the sidewalls
Implementation Method 2
After the atomization of said solution by spraying, the evaporation of water starts according to the reaction
Implementation Method 3
After the evaporation of water the urea decomposition starts according to reactions
Data Source
AI summary
The present invention provides for a method for dosing an urea-based reducing agent into a exhaust gas stream generated from a combustion engine and addressed to an aftertreatment system, e.g. SCR or SCRT system. According to the method of the invention the gas exhaust stream is conveyed into a dosing housing which develops along a longitudinal axis. In particular the gas is conveyed by generating an annular inlet jet inclined with respect of said axis. The urea-based reducing agent is injected by generating, inside the housing, an urea-based reducing agent spray which is preferably coaxial to said axis of the housing.