Angled Injection Mixer for SCR Reductant Deposit Control
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Solution Overview
Problem
Conventional exhaust aftertreatment systems for IC engines face issues with exhaust reductant deposits on sidewalls, leading to increased backpressure and potential system failure due to unwanted turbulence and reduced fuel efficiency.
Innovation Solution
A mixing assembly with a mixer comprising a plurality of plates positioned to direct exhaust reductant away from sidewalls, utilizing an injection port angled to ensure the reductant impacts only the mixer, thereby preventing deposits on the sidewalls and maintaining flow path integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If exhaust reductant is injected into the SCR system to reduce NOx gases, then NOx reduction is improved, but reductant deposits form on sidewalls causing increased backpressure and potential system failure
Solution Approach 1:
A mixer is introduced as an intermediary component between the injection port and the SCR catalyst. The mixer intercepts the exhaust reductant spray before it can reach the sidewalls, directing it toward the catalyst while preventing direct contact with the housing sidewalls. This mediator component solves the contradiction by enabling reductant delivery for NOx reduction while blocking the harmful deposition path.
Solution Approach 2:
The mixing assembly is segmented into multiple functional zones: an injection port for reductant introduction, a mixer with multiple plates for spray distribution, and a flow path guiding the mixture to the catalyst. This segmentation allows the system to control reductant flow precisely, directing it to where it is needed (catalyst) while preventing it from reaching harmful locations (sidewalls).
2Productivity
If exhaust reductant is injected at high flow rate to ensure sufficient ammonia supply, then NOx reduction performance is improved, but deposits on sidewalls increase leading to increased backpressure
Solution Approach 1:
The mixer acts as a mediator that handles high flow rates of exhaust reductant without allowing direct impact on sidewalls. By intercepting and redistributing the spray through multiple plates, the mixer enables high productivity ammonia supply while preventing the backpressure increase that would result from sidewall deposits.
Solution Approach 2:
The mixer plates are positioned to create localized flow patterns that concentrate reductant delivery in specific areas (toward the catalyst) while creating low-impact zones near the sidewalls. This local quality control allows high flow rates to be maintained without proportionally increasing harmful deposits and backpressure.
3Device complexity
If conventional mixing assembly is used without specialized mixer, then device complexity is low, but reductant deposits cause unwanted turbulence and reduced fuel efficiency
Solution Approach 1:
The mixing assembly is segmented into functional components (injection port, mixer with multiple plates, flow path) that work together to prevent turbulence. This segmentation, while increasing structural complexity, eliminates the energy loss from turbulence by ensuring smooth, directed flow of the exhaust gas-reductant mixture through the SCR system.
4Quantity of substance
If exhaust reductant is directed toward the center of the mixing assembly, then mixer impact is maximized, but precise angle control is required to prevent sidewall impact
Solution Approach 1:
The mixer plates are arranged asymmetrically in terms of their positioning and spacing to create a flow pattern that naturally directs reductant toward the center while providing a safety margin against sidewall impact. This asymmetric arrangement reduces the sensitivity to precise injection angles, allowing effective reductant delivery with more tolerant manufacturing tolerances.
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 effectively reduces reductant deposits on sidewalls, preventing backpressure increases and system failure, while ensuring compatibility with existing exhaust assemblies and SCR systems, thereby enhancing fuel efficiency and system longevity.
Implementation Method 1
A mixer is positioned within the flow path of the housing downstream of the injection port. The mixer includes a plurality of plates positioned in the flow path of the exhaust gas. A first plate of the plurality of plates is positioned distal to the injection port and adjacent to a second sidewall of the housing opposite to the first sidewall.
Implementation Method 2
An injection port is defined on a first sidewall of the housing. The injection port is oriented at a predetermined angle relative to a longitudinal axis of the flow path.
Implementation Method 3
certain exhaust aftertreatment systems for diesel-powered IC engines include a selective catalytic reduction (SCR) catalyst to convert NOx (NO and NO2 in some fraction) into harmless nitrogen gas (N2) and water vapor (H2O) in the presence of ammonia (NH3)
Implementation Method 4
an exhaust reductant, (e.g., a diesel exhaust fluid such as urea) is injected into the aftertreatment system to provide a source of ammonia, and mixed with the exhaust gas to partially reduce the NOx gases
Data Source
AI summary
An aftertreatment system comprises a SCR system. A mixing assembly is positioned upstream of the SCR system and includes a housing defining a flow path for an exhaust gas. An injection port is defined on a first sidewall of the housing and oriented at a predetermined angle relative to a longitudinal axis of the flow path. A mixer is positioned within the flow path downstream of the injection port and includes a plurality of plates each positioned in the flow path. A first plate is positioned distal to the injection port and adjacent to a second sidewall of the housing opposite to the first sidewall. The first plate has a first length substantially longer than a length of the other plates and extends in a direction upstream of the mixer. An exhaust reductant injector is positioned on the first sidewall of the housing proximal to the injection port.