Internal Box Flow Deflector for Vehicle Exhaust Mixer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The formation of urea deposits on internal surfaces of the mixer in exhaust systems can impede exhaust gas flow and reduce the performance of selective catalytic reduction (SCR) catalysts over time, as the reducing agent spray does not mix thoroughly with exhaust gases before reaching the catalyst.
Innovation Solution
A mixer assembly with a baffle and internal box configuration that includes a deflector wall to divert exhaust gases around the baffle outlet, ensuring thorough mixing of the reducing agent and exhaust gases before they enter the SCR catalyst, and an injector positioned to direct the reducing agent into the internal flow path for uniform mixing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the doser sprays the reducing agent into the exhaust stream, then the reducing agent is injected upstream of the SCR catalyst, but urea despots form on internal surfaces of the mixer which impede exhaust gas flow and reduce SCR catalyst performance
Solution Approach 1:
The mixer assembly is segmented into multiple flow paths including an internal flow path and an external flow path. The internal box with deflector walls creates separate mixing zones that allow the reducing agent to mix with exhaust gases in a controlled manner, preventing direct contact with catalyst surfaces and reducing deposit formation.
Solution Approach 2:
The internal box and deflector walls act as intermediary structures between the reducing agent injection point and the SCR catalyst. These components guide the flow and facilitate thorough mixing in the chamber, ensuring the reducing agent is properly distributed before reaching the catalyst, thereby preventing urea despots from forming on catalyst surfaces.
2Stability of the object's composition
If the spray contacts internal surfaces of the mixer, then urea despots form that impede flow, but without sufficient contact the mixing is inadequate
Solution Approach 1:
The internal box extends into the chamber to create a three-dimensional mixing structure with deflector walls that guide flow in multiple directions. This dimensional approach ensures thorough mixing by creating tortuous flow paths that increase contact between reducing agent and exhaust gases without requiring the spray to contact mixer surfaces.
Solution Approach 2:
The deflector walls are configured with curved surfaces that guide the exhaust gas and reducing agent mixture through smooth transitions. The curved geometry promotes thorough mixing by creating rotational flow patterns while minimizing direct contact between the spray and internal surfaces, reducing urea deposit formation.
3Reliability
If mixing elements are added to ensure thorough mixing, then SCR catalyst performance is maintained, but device complexity increases
Solution Approach 1:
The internal box is integrated with the baffle structure, combining multiple functions into a single component. The deflector walls are positioned within the internal box, merging the mixing function with the flow guidance function. This integration maintains SCR catalyst performance while avoiding the need for separate, additional mixing devices.
Solution Approach 2:
The internal box and deflector walls serve multiple functions: they guide exhaust gas flow, facilitate mixing of the reducing agent, prevent direct spray contact with catalyst surfaces, and maintain proper flow distribution. This multi-functionality achieves thorough mixing and protects SCR catalyst performance without adding excessive structural complexity.
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
The configuration ensures thorough mixing of the reducing agent with exhaust gases, reducing deposit formation and maintaining SCR catalyst performance by ensuring uniform distribution and effective mixing before entering the catalyst, thereby enhancing emission control and reducing noise.
Implementation Method 1
At least one deflector wall is positioned within the internal box to provide a wall surface that is spaced from the peripheral wall to define an internal flow path that diverts exhaust gas at least partially around the baffle outlet before exiting the baffle outlet
Implementation Method 2
A mixer is positioned upstream of the SCR catalyst and mixes engine exhaust gases and products of urea transformation
Data Source
AI summary
A mixer includes a baffle having a baffle inlet receiving exhaust gas from an upstream exhaust component and a baffle outlet directing exhaust gas to a downstream exhaust component. A cover provides a chamber between an internal surface of the cover and the baffle. An internal box is positioned within the chamber to cover the baffle outlet and includes a bottom wall with a peripheral wall extending about at least a portion of an outer periphery of the bottom wall. At least one deflector wall is positioned within the internal box to provide a wall surface that is spaced from the peripheral wall to define an internal flow path that diverts exhaust gas at least partially around the baffle outlet before exiting the baffle outlet. An opening is located in the peripheral wall to receive exhaust gas exiting the inlet and to direct exhaust gas into the internal flow path.