SCR Efficiency Isolation in Exhaust Aftertreatment Systems
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Solution Overview
Problem
Current on-road diagnostic procedures for exhaust aftertreatment systems are limited in detecting and correcting component failures due to operational constraints, which can hinder the effective reduction of emissions and may require multiple diagnostic tests, increasing time and resource usage.
Innovation Solution
A system and method that utilize a controller to analyze NOx data from a selective catalytic reduction (SCR) system across varying inlet temperatures, allowing for the determination of SCR efficiency and thereby isolating component failures in the SCR, diesel oxidation catalyst (DOC), and diesel particulate filter (DPF) systems, reducing the need for multiple diagnostic procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If on-road monitoring and testing are performed during normal vehicle operation, then convenience is improved, but diagnostic efficacy is worsened due to operational constraints and limited operating ranges
Solution Approach 1:
The system performs preliminary diagnostic actions by injecting a known amount of reductant into the exhaust stream before actual component failure occurs. This allows the system to establish baseline performance metrics and detect deviations that indicate component degradation, enabling early intervention while the system is still operational but before failure occurs.
Solution Approach 2:
The system changes operational parameters by introducing controlled amounts of reductant (ammonia or urea) into the exhaust stream during diagnosis. This chemical parameter change allows the system to test SCR catalyst performance under controlled conditions, overcoming the limitations of normal operating variability and enabling more reliable diagnostics during on-road operation.
2Measurement precision
If multiple diagnostic tests are performed to isolate component failures, then measurement precision is improved, but loss of time is worsened
Solution Approach 1:
The system merges multiple diagnostic functions into a single integrated test procedure. By combining reductant injection, NOx concentration measurement, and temperature monitoring into one coordinated diagnostic routine, the system achieves comprehensive component assessment (SCR catalyst efficiency, DOC performance, DPF status) without requiring sequential execution of separate tests, thereby reducing diagnostic time while maintaining precision.
Solution Approach 2:
The system uses feedback from NOx sensor measurements and temperature data to dynamically adjust diagnostic conclusions. By continuously monitoring the relationship between injected reductant amount, exhaust temperature, and downstream NOx concentrations, the system can isolate specific component failures with high precision through a single integrated test rather than multiple sequential tests.
3Productivity
If on-road diagnostic procedures are used, then operational continuity is improved, but diagnostic accuracy is worsened due to uncontrolled operating conditions
Solution Approach 1:
The system introduces an intermediary substance (known amount of reductant) into the exhaust stream to mediate the diagnostic process. This controlled chemical addition creates a standardized test condition that overrides the variability of normal operating conditions, allowing accurate measurement of SCR catalyst performance and downstream component status even during on-road operation with uncontrolled ambient conditions.
Solution Approach 2:
The system deliberately changes exhaust composition parameters by injecting precise amounts of reductant, transforming uncontrolled on-road operating conditions into a controlled diagnostic state. This parameter change enables accurate measurement of system component performance by creating a known input condition (reductant injection rate) that can be correlated with output measurements (downstream NOx levels).
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 enables quicker and more efficient diagnosis of exhaust aftertreatment system components, saving time and resources by identifying component failures through a single, intrusive diagnostic process, thus minimizing downtime and operational costs.
Implementation Method 1
a selective catalytic reduction (SCR) system
Implementation Method 2
determine a first SCR efficiency based on the second set of NOx data; determine a second SCR efficiency based on the third set of NOx data
Implementation Method 3
a diesel oxidation catalyst (DOC)
Implementation Method 4
a catalyzed diesel particulate filter (DPF)
Data Source
AI summary
An apparatus includes a dosing module structured to suspend dosing in an exhaust aftertreatment system; a selective catalytic reduction (SCR) inlet NOx module structured to interpret SCR inlet NOx data and an SCR inlet temperature; a SCR outlet NOx module structured to interpret SCR outlet NOx data; and a system diagnostic module structured to determine an efficiency of a SCR system based on the SCR inlet and outlet NOx data over a range of SCR temperatures, wherein the system diagnostic module is further structured to determine a state of at least one of a diesel oxidation catalyst (DOC), a diesel particulate filter (DPF), and the SCR system based on the SCR efficiency at an elevated SCR temperature range and the SCR efficiency at a relatively lower SCR temperature range relative to a high SCR efficiency threshold and a low SCR efficiency threshold.