DEF Decomposition Tube Regeneration Controller
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Solution Overview
Problem
Conventional exhaust aftertreatment systems for internal combustion engines face issues with inadequate decomposition and mixing of diesel exhaust fluid (DEF) leading to solid deposits in the decomposition tube, resulting in uneven ammonia distribution, reduced NOx conversion efficiency, and diagnostic faults, which can cause false engine and exhaust system performance issues.
Innovation Solution
A system and method that includes an on-board diagnostic (OBD) system to monitor diagnostic signals and request regeneration of the DEF decomposition tube before faults occur, ensuring proper decomposition of DEF deposits and maintaining NOx reduction capability, thereby reducing unnecessary diagnostic faults and improving engine and aftertreatment system performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DEF is injected into the exhaust gas stream for SCR catalyst operation, then NOx reduction capability is improved, but solid DEF deposits form on the decomposition tube walls leading to diagnostic faults
Solution Approach 1:
The system performs preliminary action by monitoring diagnostic signals and requesting regeneration of the decomposition tube before actual faults occur. The controller detects early signs of deposit formation through diagnostic signal analysis and initiates regeneration events proactively, preventing the harmful effect of solid DEF deposits from developing into actual diagnostic faults that would compromise system reliability.
Solution Approach 2:
The system implements feedback by continuously monitoring diagnostic signals related to decomposition tube conditions and using this information to trigger regeneration events. The controller receives feedback from the monitoring system about deposit formation trends and adjusts regeneration timing accordingly, creating a closed-loop control system that maintains optimal operation while preventing harmful deposit accumulation.
2Reliability
If regeneration events are performed frequently to remove DEF deposits, then deposit formation is controlled, but system complexity and operational interruptions increase
Solution Approach 1:
The monitoring system performs preliminary analysis of diagnostic signals to predict when deposit levels will reach problematic thresholds. By calculating future deposit accumulation trends based on current operational parameters and historical data, the system can schedule regeneration events optimally in advance, balancing deposit control requirements with operational continuity needs without requiring complex real-time control during regeneration.
3Stability of the object's composition
If DEF decomposition and mixing is enhanced to prevent deposits, then ammonia distribution uniformity is improved, but decomposition tube temperature requirements increase
Solution Approach 1:
The system applies parameter changes by adjusting operational parameters such as DEF injection rate, exhaust gas flow rate, and decomposition tube residence time to optimize the balance between decomposition completeness and temperature requirements. By dynamically modifying these parameters based on monitored conditions, the system achieves adequate ammonia distribution uniformity while preventing excessive temperature increases that would be required for more aggressive decomposition enhancement.
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 approach effectively mitigates the adverse effects of DEF deposits by preventing diagnostic faults and enhancing NOx reduction efficiency, improving the overall performance and reducing maintenance costs of the engine and exhaust aftertreatment systems.
Implementation Method 1
the temperature of the exhaust causes a thermolysis-induced phase change in the DEF and decomposition of the DEF into isocyanic acid (HNCO) and NH3
Implementation Method 2
the isocyanic acid reacts with water in a hydrolysis process under specific pressure and temperature concentrations to decompose into ammonia and carbon dioxide (CO2)
Implementation Method 3
Upon injection into the exhaust gas stream, the injected DEF spray is heated by the exhaust gas stream to trigger the decomposition of DEF into ammonia
Data Source
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AI summary
According to one embodiment, described herein is an apparatus for mitigating on-board diagnostic (OBD) faults generated by an OBD system of an internal combustion engine (ICE) system (10) having a selective catalytic reduction system (230) with a diesel exhaust fluid (DEF) decomposition tube (239). The apparatus includes a fault mitigation module (320) that is configured to monitor at least one OBD signal of the OBD system and issue a request (325) for regenerating the DEF decomposition tube when a value of the at least one OBD signal reaches a predetermined regeneration threshold corresponding with the at least one OBD signal. The regeneration threshold is reachable prior to an OBD fault threshold corresponding with the at least one OBD signal. The apparatus also includes a regeneration module (340) that is configured to regenerate the DEF decomposition tube according to the issued request.