Exhaust Gas Inlet Section with Flow Deflection for Urea Decomposition
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Solution Overview
Problem
Existing exhaust gas aftertreatment systems for internal combustion engines, particularly lean-running engines, face challenges in achieving complete decomposition of reducing agents like urea due to uneven distribution and low exhaust gas temperatures, leading to the formation of solid deposits and reduced nitrogen oxide conversion efficiency.
Innovation Solution
A device with a reducing agent decomposition catalytic converter, a dosing device for aqueous urea, and an inlet section with flow deflection areas that allow counterflow heating, combined with throttling and turbulence control, ensures uniform distribution and rapid heating of the reducing agent, preventing deposits and enhancing decomposition efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the reducing agent is supplied directly into the exhaust gas stream without flow deflection areas, then the device complexity is reduced, but the uniformity of reducing agent distribution deteriorates leading to local deposits
Solution Approach 1:
The inlet section is segmented into multiple flow deflection areas that divide the exhaust gas flow into different pathways. This segmentation ensures that the reducing agent is distributed more uniformly across the catalyst cross-section by preventing localized concentration and avoiding flow dead zones.
Solution Approach 2:
The inlet section extends in the longitudinal direction of the exhaust pipe, creating an elongated flow path. This dimensional extension allows for better mixing and distribution of the reducing agent across the catalyst inlet cross-section, transforming a potentially problematic 3D flow issue into a controlled sequential process.
2Stability of the object's composition
If the inlet section is extended to improve distribution, then the uniformity of reducing agent distribution is improved, but the length of the device increases
Solution Approach 1:
The flow deflection areas are positioned upstream in the inlet section to preemptively address distribution issues before the reducing agent reaches the catalyst. By cushioning and preparing the flow pattern in advance, the system achieves uniform distribution without requiring excessive length downstream.
Solution Approach 2:
The inlet section incorporates a porous structure with multiple flow deflection areas that create numerous small flow pathways. This porous-like configuration increases the effective surface area for mixing and distribution while maintaining a compact overall length, preventing both flow dead zones and cross-sectional jumps.
3Use of energy by moving object
If the exhaust gas temperature is low, then the energy consumption is reduced, but the decomposition efficiency of the reducing agent deteriorates leading to cyanuric acid formation
Solution Approach 1:
The flow deflection areas and turbulence promotion features are positioned upstream to preliminarily mix and distribute the reducing agent uniformly across the exhaust gas stream before it reaches the catalyst. This preliminary action ensures that even at lower temperatures, the reducing agent is evenly distributed and can decompose efficiently without forming local deposits of cyanuric acid.
4Productivity
If the reducing agent is concentrated in local areas, then the dosing efficiency is improved, but the formation of solid deposits increases due to insufficient heat distribution
Solution Approach 1:
The inlet section creates locally optimized flow conditions through multiple flow deflection areas, where each local region receives an appropriate amount of reducing agent distributed according to the local exhaust gas flow characteristics. This local quality approach prevents both over-concentration (which would cause deposits) and under-dosing (which would reduce efficiency).
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 allows for quantitative decomposition of reducing agents without impairing engine efficiency, ensuring effective nitrogen oxide reduction and minimizing unwanted deposits, even under low exhaust gas temperatures.
Implementation Method 1
the exhaust gas is fed radially outside of an inlet pipe connected to the reducing agent decomposition catalytic converter in a housing section surrounding the inlet pipe and is conducted in counterflow via an inlet opening on the front of the inlet pipe
Implementation Method 2
at least one reducing agent decomposition catalytic converter, in particular a hydrolysis catalytic converter, connected in the exhaust gas stream
Implementation Method 3
after HNCO +H 2 O → NH 3 + CO 2 , hydrolysis occurs, i.e. the catalytic decomposition of isocyanic acid (HNCO) into ammonia (NH 3 ) and carbon dioxide (CO 2 )
Implementation Method 4
After (NH 2 ) 2 CO → NH 3 + HNCO, the first step is thermolysis, i.e. the thermal decomposition of urea
Data Source
Figure 1
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AI summary
The invention relates to a device for the aftertreatment of exhaust gases in an exhaust system of internal combustion engines, in particular of lean-running internal combustion engines for motor vehicles, with at least one reducing agent decomposition catalyst, in particular a hydrolysis catalyst, connected in the exhaust gas stream, and a metering device arranged upstream in an exhaust gas line for supplying reducing agent, in particular for supplying an aqueous urea solution, wherein at least one further catalyst device, in particular at least one SCR catalyst, is preferably connected downstream of the reducing agent decomposition catalyst.According to the invention, an inlet section (10) for the exhaust gas, having at least one flow deflection region (15a, 15b), is connected upstream of the reducing agent decomposition catalyst (9), which is designed such that the exhaust gas is supplied radially outside an inlet pipe (14) adjoining the reducing agent decomposition catalyst (9) in a housing section (11a, 11b) surrounding the inlet pipe (14) and is guided in counterflow via an end-face inlet opening (15) of the inlet pipe (14) to the reducing agent decomposition catalyst (9), wherein the reducing agent is supplied in the flow deflection region (15a) of the exhaust gas stream associated with the inlet opening (15).