Switchable Exhaust Gas Flow System for NOx Reduction
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Solution Overview
Problem
Current exhaust gas aftertreatment systems for combustion engines face inefficiencies in nitrogen oxide reduction across varying engine operating conditions, particularly due to the temperature-dependent performance of nitrogen oxide storage catalytic converters and selective catalytic reduction systems, which affects overall emission control effectiveness.
Innovation Solution
A switchable exhaust gas flow system with a rotatable plate and fixed plate arrangement, allowing exhaust gas to be directed through inner or outer regions of a catalytic converter device based on engine operating conditions, optimizing the use of nitrogen oxide storage catalytic converters and oxidation catalytic converters to enhance nitrogen oxide reduction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If exhaust gas is passed through nitrogen oxide storage catalytic converter (LNT), then nitrogen oxide reduction efficiency is improved at low temperatures, but the system cannot effectively handle high-temperature operating conditions
Solution Approach 1:
The patent implements a dynamic flow distribution system using a rotatable plate with selectively openable inner and outer circumferential flow channels. The system dynamically redirects exhaust gas flow between the LNT (inner channel) and oxidation catalytic converter (outer channel) based on real-time temperature conditions, allowing the LNT to operate efficiently within its optimal temperature range while bypassing it when temperatures exceed operational limits.
Solution Approach 2:
The control system monitors exhaust gas temperature and adjusts the flow distribution parameters by rotating the plate to different positions. When temperature is within the LNT's optimal range (150-500°C), the inner flow channel is opened to direct exhaust through the LNT. When temperature exceeds this range, the plate rotates to close the inner channel and open the outer channel, redirecting flow to the oxidation catalytic converter.
2Productivity
If exhaust gas flow is increased through the catalytic converter device, then emission treatment capacity is improved, but the temperature control precision deteriorates
Solution Approach 1:
The patent divides the exhaust gas flow into two separate circumferential channels (inner and outer) that can be independently controlled. This segmentation allows different portions of the exhaust flow to be directed through different catalytic converter regions, enabling precise temperature management while maintaining high overall treatment capacity. The rotatable plate with selective channel opening/closing provides granular control over flow distribution.
3Device complexity
If a single catalytic converter design is used, then device complexity is reduced, but the effectiveness across varying engine operating conditions deteriorates
Solution Approach 1:
The patent integrates two distinct catalytic converter functions (LNT and oxidation catalytic converter) into a single unified device with a common housing and shared exhaust flow path. The LNT handles nitrogen oxide storage and reduction at lower temperatures, while the oxidation catalytic converter manages hydrocarbon and carbon monoxide oxidation and provides thermal management at higher temperatures. This multi-functional design enables one device to effectively handle the full range of engine operating conditions.
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 solution improves exhaust gas treatment efficiency by adjusting exhaust gas flow according to temperature and velocity thresholds, ensuring optimal operation of nitrogen oxide storage and oxidation catalytic converters, thereby enhancing nitrogen oxide reduction and overall emission control.
Implementation Method 1
The LNT may oxidize the nitrogen monoxide (NO) contained in the lean exhaust gas to form nitrogen dioxide (NO2) and then stores it in the form of nitrates
Implementation Method 2
LNTs may be used for adsorption of oxides of nitrogen from the exhaust gas of combustion engines
Implementation Method 3
catalytic converters are used for selective catalytic reduction (SCR). For this, ammonia can be introduced into the exhaust system upstream of the SCR
Implementation Method 4
nitrogen oxide is reduced to gaseous nitrogen and water using a reducing agent, (e.g., ammonia)
Implementation Method 5
carbon monoxide is oxidized to carbon dioxide and hydrocarbons are oxidized to carbon dioxide and water
Data Source
AI summary
Methods and systems are provided for a flow device shaped to adjust flow to radial positions of an emission control device. In one example, a system may include where the flow device comprises a plurality of inner openings that align while a plurality of outer openings are misaligned to flow exhaust gas proximal to a central axis of an exhaust passage, and where the plurality of outer openings are aligned and the plurality of inner openings are misaligned to flow exhaust gas distal to the central axis.