Exhaust Flow Device with Bent Tubes for Reactant Mixing
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Solution Overview
Problem
Existing exhaust treatment systems for diesel engines face inefficiencies in mixing exhaust gases and reactants, such as urea or ammonia, which affects the performance of aftertreatment devices like selective catalytic reduction (SCR) catalysts, leading to incomplete vaporization and decomposition of reactants at low temperatures, resulting in reduced NOx reduction efficiency.
Innovation Solution
A flow device with bent tubes and a baffle is integrated into the exhaust conduit to redirect exhaust flow, creating a swirl angle of 45 to 135 degrees, ensuring uniform mixing of reactants with exhaust gases and enhancing vaporization and decomposition, while a hydrolysis catalyst is used to facilitate complete reactant conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If reactants are injected into exhaust gas without flow redirection, then the injection process is simple, but the mixing of reactants with exhaust gases is non-uniform
Solution Approach 1:
The patent employs bent tubes with curved geometries to redirect exhaust flow. The curvature of these tubes creates swirl motion in the exhaust gas, which enhances the mixing of injected reactants with exhaust gases, achieving uniform distribution without complicating the injection process
2Device complexity
If straight tubes are used for exhaust flow, then the device structure is simple, but the vaporization and decomposition of reactants is incomplete especially at low temperatures
Solution Approach 1:
The bent tube configuration with specific curvature radii creates turbulent flow patterns and extends the residence time of reactants in the hot exhaust environment. This curvature-induced turbulence enhances heat transfer and promotes complete vaporization and decomposition of reactants even at lower exhaust temperatures
Solution Approach 2:
The patent designs the bent tubes to dynamically adapt to varying exhaust flow conditions. The curved geometry creates flow separation and reattachment zones that generate turbulence, which dynamically enhances mixing and vaporization processes under different operating conditions
3Productivity
If conventional mixing methods are used, then the axial distance required for mixing is long, but the aftertreatment device length increases
Solution Approach 1:
The bent tubes with optimized curvature radii create immediate swirl motion upon exhaust entry, which rapidly distributes injected reactants throughout the exhaust stream. This curvature-induced mixing action significantly reduces the axial distance required to achieve uniform mixing, allowing compact aftertreatment device design
4Device complexity
If reactants are not properly mixed with exhaust gases, then the injection system is simple, but the NOx reduction efficiency decreases
Solution Approach 1:
The bent tube configuration creates turbulent flow patterns that thoroughly mix injected reactants with exhaust gases, ensuring uniform distribution across the catalyst surface. This curvature-induced turbulence maintains high NOx reduction efficiency without requiring complex multi-point injection systems
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 achieves a uniform mixture of exhaust gases and reactants over a shorter axial distance, improves reactant vaporization and decomposition, and increases the efficiency of NOx reduction in aftertreatment devices, even at low temperatures, by utilizing centrifugal force to retain unvaporized reactants and ensuring effective distribution of catalysts for enhanced performance.
Implementation Method 1
utilizing centrifugal force to retain unvaporized reactants
Implementation Method 2
improves reactant vaporization and decomposition
Implementation Method 3
a hydrolysis catalyst is used to facilitate complete reactant conversion
Data Source
Figure 1
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AI summary
A flow device (23) for an exhaust treatment system includes a base (39) and a least one flow deflector tube (41) secured to the base. The flow deflector tube includes a flow inlet, a flow outlet, and a passage that extends through the flow deflector tube from the flow inlet to the flow outlet. The flow outlet is at an angled orientation to the flow inlet A method of mixing reactants and exhaust in an exhaust treatment system includes the steps of injecting reactants into exhaust gases flowing through an exhaust conduit use to convey the exhaust gases from an engine. Bent tubes are disposed in the exhaust conduit and used to mix the exhaust gases and the reactants.