Exhaust Gas Mixing Unit with Deflection Flow Path
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Solution Overview
Problem
In compact exhaust systems, there is a challenge in efficiently mixing exhaust gas with a reactant, such as a urea/water solution, due to potential condensation and deposition on housing surfaces and insufficient mixing, which can lead to reduced effectiveness of catalytic reactions in SCR catalytic converters.
Innovation Solution
An exhaust gas/reactant mixing arrangement with a mixing chamber and flow path design that includes multiple deflection regions and partition walls to create turbulences and guide the mixture stream, ensuring efficient mixing and minimizing contact with the housing wall, featuring a mixture flow path with a first and second flow deflection region and an exhaust gas flow space for thermal decoupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the distance between reactant injection location and SCR catalyst assembly is reduced for compact exhaust system design, then the exhaust system becomes more compact, but mixing efficiency between exhaust gas and reactant deteriorates
Solution Approach 1:
The mixing chamber is segmented into distinct functional regions: a reaction agent discharge region, a first flow deflection region, a second flow deflection region, and a mixture discharge region. This segmentation allows each region to perform its specific function optimally while maintaining a compact overall structure. The partition walls create separate zones that facilitate controlled flow paths and efficient mixing within limited space.
Solution Approach 2:
The patent introduces multiple flow deflection regions that redirect the mixture flow in different directions (first deflection direction and second deflection direction opposite to the first). This multi-dimensional flow management increases the effective mixing path length and improves turbulence without increasing the linear distance between injection and catalyst assembly, thus maintaining compactness while enhancing mixing efficiency.
2Reliability
If reactant is injected in liquid form to reduce nitrogen oxide content, then catalytic reduction effectiveness improves, but condensation and deposition on housing inner surface increases
Solution Approach 1:
The harmful contact between liquid reactant and housing inner surface is extracted and eliminated by introducing partition walls that create a separate reaction agent discharge region. The liquid reactant is confined to this enclosed region where it mixes with exhaust gas before being discharged through controlled openings, preventing direct contact with and deposition on the housing inner surface while maintaining catalytic reduction effectiveness.
Solution Approach 2:
The partition walls and controlled discharge openings act as intermediaries between the liquid reactant and the housing inner surface. These structural elements mediate the flow path, ensuring the liquid reactant remains confined to the mixing chamber and discharges only through designated openings, thereby preventing condensation and deposition on the housing while enabling effective catalytic reduction.
3Volume of moving object
If insufficient mixing occurs between exhaust gas and reactant, then compact design is maintained, but liquid reactant enters SCR catalyst assembly making it unavailable for catalytic reaction
Solution Approach 1:
The mixing chamber employs dynamic flow management through multiple flow deflection regions that actively redirect the mixture flow. The first and second flow deflection regions create turbulent flow patterns and extend the residence time of the mixture within the chamber, ensuring thorough mixing and complete evaporation of liquid reactant before discharge, thereby maintaining reactant availability for catalytic reaction while keeping the chamber compact.
Solution Approach 2:
The patent changes flow parameters by introducing multiple flow deflection directions and controlled discharge opening configurations. These parameter changes in flow path geometry and direction increase mixing efficiency and ensure complete reactant vaporization before the mixture exits the mixing chamber, preventing liquid reactant from reaching the SCR catalyst assembly while maintaining a compact volume.
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 design achieves efficient mixing of exhaust gas and reactant, reducing the risk of deposition and ensuring effective catalytic reactions, while maintaining a compact structure suitable for linear succession with other exhaust treatment units.
Implementation Method 1
The mixture flow path has two flow deflection regions following one another in a mixture flow direction, with mutually opposite flow deflection directions
Data Source
Figure 1~2
Figure 3~4
AI summary
An exhaust gas/reaction agent mixing arrangement for an exhaust system (10) of an internal combustion engine for mixing exhaust gas and reaction agent (R) comprises an exhaust gas guide housing (18) extending in the direction of a housing longitudinal axis (G) with a housing wall (20), wherein an exhaust gas channel (30) surrounded by the housing wall (20) and through which exhaust gas flows is formed in the exhaust gas guide housing (18), a mixing zone (36) with a mixing chamber (42) formed between an upstream end wall (38) and a downstream end wall (40) arranged with respect to the upstream end wall (38), and a reaction agent discharge arrangement (46) carried on the exhaust gas guide housing (18) for discharging reaction agent (R) into the mixing chamber (42) substantially along a reaction agent discharge line (L) in a main reaction agent discharge direction (H).wherein in the mixing chamber (42) a mixture flow path (62) is formed leading from the at least one first inlet opening (48) to the at least one first outlet opening (50, 52, 54), wherein the mixture flow path (62) has two successive flow deflection regions (64, 68) in a mixture flow direction (S) with flow deflection directions opposite to each other.