Exhaust Aftertreatment System with Parallel DOC and SCR Streams
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Solution Overview
Problem
Existing exhaust aftertreatment systems face challenges in achieving optimal NO to NO2 ratios for effective SCR operations, particularly in engines producing a 95:5 NO to NO2 ratio, and may not be suitable for all applications due to size and backpressure constraints.
Innovation Solution
The system includes a housing with multiple inlets and redirecting flow passages to combine and split exhaust streams through DOC and SCR catalysts in a specific configuration, with a reductant introduction system, to achieve a 50:50 NO to NO2 ratio while maintaining compact size and low backpressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional single-stream exhaust aftertreatment system is used, then the system structure is simple, but the NO to NO2 ratio cannot be optimized to 50:50 for effective SCR operations
Solution Approach 1:
The exhaust stream is divided into multiple parallel streams, each processed through separate DOC and SCR catalyst beds. This segmentation allows independent optimization of each stream's chemical reactions, enabling precise control over the overall NO to NO2 ratio while maintaining manageable system complexity through modular architecture
Solution Approach 2:
Multiple exhaust streams are merged after individual treatment to achieve the target 50:50 NO to NO2 ratio. The merging combines the effects of parallel DOC and SCR processing, where one stream converts NO to NO2 while another maintains NO, achieving the desired balance for optimal SCR operation
2Ease of operation
If a preassembled common housing system is used to facilitate easier installation, then the ease of installation is improved, but the system size and backpressure may not be suitable for all applications
Solution Approach 1:
The system is divided into modular parallel streams with separate DOC and SCR catalyst beds that can be independently sized and configured. This modular segmentation allows the system to be adapted to different application requirements while maintaining the benefit of preassembled housing for ease of installation
Solution Approach 2:
The system incorporates adjustable flow distribution between parallel streams, allowing dynamic optimization of exhaust flow paths. This enables the same preassembled housing to adapt to different backpressure requirements and application-specific performance needs
3Reliability
If multiple DOC and SCR catalyst beds are used in parallel to achieve optimal NO to NO2 ratio, then the emissions treatment effectiveness is improved, but the system volume increases
Solution Approach 1:
The parallel DOC and SCR catalyst beds are arranged in a compact nested configuration within the preassembled housing. One catalyst bed is positioned to utilize the space efficiently alongside the other, reducing overall system volume while maintaining the effectiveness of multiple treatment streams
Solution Approach 2:
The system transitions from a single linear exhaust path to a multi-dimensional parallel stream architecture. By processing exhaust through multiple spatial pathways simultaneously, the system achieves enhanced treatment effectiveness without proportionally increasing the footprint or volume of the housing
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 effectively treats exhaust emissions by achieving the desired NO to NO2 ratio, reducing emissions, and ensuring low backpressure and compact design suitable for various applications, including locomotives.
Implementation Method 1
a diesel oxidation catalyst (DOC) may be located upstream of the SCR catalyst to convert NO to NO2
Implementation Method 2
a catalyst facilitates a reaction between a reductant, such as ammonia, and NOx to produce water and nitrogen gas
Implementation Method 3
a catalyst facilitates a reaction between a reductant, such as ammonia, and NOx to produce water and nitrogen gas, thereby removing NOx from the exhaust gas
Data Source
AI summary
An exhaust aftertreatment system including a housing with two or more inlets configured to receive separate entering exhaust streams from an engine. The system may include two or more first exhaust treatment devices, each configured to receive one of the separate entering exhaust streams in a first direction. The system may further include two or more redirecting flow passages configured to combine the separate exhaust streams into a merged exhaust stream that flows in a second direction about 180 degrees from the first direction and an intermediate flow region configured to divide the merged exhaust stream into two or more separate exiting exhaust streams. The system also may also includes two or more second exhaust treatment devices, each configured to receive one of the separate exiting exhaust streams in a third direction about 90 degrees from the second direction.