Multi-Vane Mixer for SCR Reductant Mixing
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Solution Overview
Problem
Conventional exhaust aftertreatment systems face challenges in effectively mixing reductant with exhaust gas, leading to reductant deposits that reduce the efficiency of selective catalytic reduction (SCR) catalysts.
Innovation Solution
A multi-vane mixer with a central hub and a reductant injector that inserts reductant at a non-zero angle relative to the transverse axis, opposite the circumferential direction of exhaust gas rotation, is used to enhance mixing and reduce reductant deposits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a conventional reductant injector is used to insert reductant into exhaust gas, then the reductant can be delivered to the SCR system, but the reductant is not adequately mixed with the exhaust gas leading to reductant deposits forming on walls and components
Solution Approach 1:
The mixer divides the exhaust gas flow into multiple streams using vanes, creating separate flow paths that enhance mixing with injected reductant. The segmented flow structure ensures better distribution and prevents deposit formation on walls.
Solution Approach 2:
The mixer acts as an intermediary device between the reductant injector and the SCR catalyst. It facilitates thorough mixing of reductant with exhaust gas before the mixture reaches the SCR system, preventing direct contact of unmixed reductant with walls and components.
2Ease of operation
If mixers are used to facilitate mixing of reductant with exhaust gas, then mixing is improved, but reductant deposit formation remains a challenge due to insufficient mixing effectiveness
Solution Approach 1:
The mixer employs asymmetric vane angles and configurations that create controlled swirl patterns in the exhaust gas flow. This asymmetric design enhances mixing effectiveness by creating turbulent flow patterns that thoroughly distribute reductant throughout the exhaust stream.
Solution Approach 2:
The mixer changes the flow parameters of exhaust gas through swirl generation and flow direction alteration. By modifying velocity distribution and creating rotational flow, the mixer enhances mixing efficiency and prevents reductant deposits from forming on surfaces.
3Ease of operation
If the reductant injector is mounted offset from the flow axis to facilitate mixing, then some mixing is achieved, but reductant deposits still form on walls and various components of the aftertreatment system
Solution Approach 1:
The mixer introduces a rotational dimension to the exhaust gas flow by creating swirl patterns. This adds a third dimension of motion to the primarily axial flow, enhancing mixing through three-dimensional turbulent patterns that prevent reductant from settling on walls.
Solution Approach 2:
The mixer creates dynamic, time-varying flow patterns through swirl generation. The rotational and turbulent flow characteristics continuously change the distribution of reductant and exhaust gas, preventing static deposit formation on surfaces while maintaining effective mixing.
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 solution provides improved mixing of reductant with exhaust gas, reducing reductant deposits and maintaining the efficiency of the SCR catalytic conversion, while also minimizing flow recirculation and allowing for dynamic control of reductant distribution.
Implementation Method 1
a plurality of vanes extending from the hub to the tubular member such that openings are defined between adjacent vanes of the plurality of vanes to allow the exhaust gas to flow therethrough such that the plurality of vanes swirl the exhaust gas in a circumferential direction
Implementation Method 2
a reductant injector that inserts reductant at a non-zero angle with respect to the transverse axis of the aftertreatment system and opposite a circumferential direction of rotation of the exhaust gas
Data Source
AI summary
An aftertreatment system comprises: a housing, a SCR system disposed in the housing. A mixer is disposed upstream of the SCR system and includes: a hub, a tubular member disposed circumferentially around the hub and defining a reductant entry port, and plurality of vanes extending from the hub to the tubular member such that openings are defined between adjacent vanes. The plurality of vanes swirl the exhaust gas in a circumferential direction. A reductant injector is disposed on the housing upstream of the SCR system along a transverse axis and configured to insert a reductant into the exhaust gas flowing through the housing through the reductant entry port. The reductant is inserted at a non-zero angle with respect to the transverse axis opposite the circumferential direction to achieve virtual interception. A mixer central axis is radially offset with respect to a housing central axis of the housing.