Reductant Delivery Flow Offset Diagnosis
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Solution Overview
Problem
Current selective catalytic reduction (SCR) systems for diesel engines face challenges in diagnosing reductant delivery system blockages, which can lead to inadequate NOx conversion due to insufficient reductant flow, as existing systems fail to accurately detect and report malfunctions in the reductant delivery system.
Innovation Solution
A system comprising a reductant delivery system with a controller that determines a flow rate offset value and calculates a reductant flow rate error, allowing for the output of a performance status indicative of the system's performance based on the error and a predetermined threshold, enabling more accurate diagnosis of blockages and performance issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If SCR systems use reductant delivery systems to introduce reductant into the exhaust stream, then NOx conversion rates are improved, but the system becomes vulnerable to blockages and flow restrictions that reduce reductant delivery
Solution Approach 1:
The system continuously monitors reductant flow rate and compares it against expected values to detect blockages. The controller receives feedback from flow rate measurements and adjusts pump operation accordingly, enabling real-time detection and response to delivery system deterioration.
Solution Approach 2:
The system performs preliminary diagnostics by measuring flow rate offset values and comparing them against threshold criteria before actual NOx conversion occurs. This early detection prevents severe blockages from developing and allows proactive maintenance.
2Productivity
If the reductant pump operates at high flow rates to ensure adequate reductant delivery, then NOx conversion is improved, but the system becomes more sensitive to blockages and flow restrictions
Solution Approach 1:
The system monitors the relationship between pump command values and actual flow rates, detecting deviations that indicate blockages. This feedback mechanism allows the system to identify when high flow rates are compromised by restrictions, enabling corrective action before NOx conversion is affected.
Solution Approach 2:
The system changes operational parameters by adjusting pump command values based on detected flow rate offset values. When blockages are detected, the controller modifies pump operation to maintain adequate flow despite restrictions, optimizing performance under varying system conditions.
3Reliability
If existing diagnostic systems monitor NOx conversion performance, then system effectiveness is improved, but the ability to diagnose specific reductant delivery blockages is insufficient
Solution Approach 1:
The system introduces flow rate offset value as an intermediary parameter that mediates between pump command values and actual reductant delivery. This intermediate measurement enables indirect detection of blockages without directly observing the exhaust stream, simplifying the diagnostic process.
Solution Approach 2:
The system replaces direct mechanical inspection of the reductant delivery system with electronic sensing and computational analysis. By substituting physical blockage detection with flow rate measurement and offset value calculation, the system achieves more reliable and easier-to-implement diagnostics.
Data Source
AI summary
A system for diagnosing and/or determining the performance of a reductant delivery system may include determining a flow rate offset value for the reductant delivery system. A reduced reductant flow rate may be determined for a reductant dosing command value based, at least in part, on the determined flow rate offset when reductant dosing command is non-zero. A reductant flow rate error can be determined based, at least in part, on a difference between an expected reductant flow rate value corresponding to the reductant dosing command value and the determined reduced reductant flow rate. A performance status value indicative of a performance status of the reductant delivery system may be outputted based, at least in part, on the determined first reductant flow rate error and a predetermined threshold.