Reagent Doser Pressure Diagnostic System
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Solution Overview
Problem
Existing SCR systems face issues with urea crystal growth and deposits, leading to blockages and insufficient reagent injection, which current monitoring techniques fail to reliably diagnose, resulting in false failures and increased costs.
Innovation Solution
A diagnostic system that includes a controller and pressure sensor to monitor reagent dosing pressure drops during a modified dosing cycle, allowing for real-time detection of blockages and faults by suspending pressure feedback control and extending the diagnostic dosing period to ensure accurate reagent delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing monitoring techniques (comparing commanded volume to consumed volume) are used to diagnose dosing system failures, then the system can detect potential faults, but the technique produces false failures and unreliable diagnostics due to operator re-fill behavior, reagent tank geometry, sensor resolution, and overfill volume
Solution Approach 1:
The patent replaces mechanical/volumetric measurement methods with pressure-based sensing. Instead of measuring reagent volume directly (which is affected by tank geometry, overfill, and sensor resolution), the system uses pressure sensors to detect flow restrictions and dosing failures. The pressure differential across the dosing system provides a reliable indicator of system health independent of volumetric measurement errors.
Solution Approach 2:
The patent introduces pressure as an intermediary parameter to indirectly measure dosing system performance. Rather than directly measuring reagent volume delivery (which suffers from multiple error sources), the system measures pressure changes that result from dosing failures. This intermediary measurement approach isolates the diagnostic system from the sources of volumetric measurement error.
2Measurement precision
If a flow meter and associated sensing hardware are placed in the dosing system to provide real-time measurement of flow rate, then accurate flow monitoring is achieved, but the hardware cost and maintenance costs increase significantly
Solution Approach 1:
The patent extracts the diagnostic function from the main dosing system and implements it using existing pressure sensing infrastructure. Instead of adding flow meters to the dosing line, the system uses pressure sensors at strategic locations to infer flow conditions. This separates the measurement function from the dosing function, avoiding the need for complex flow measurement hardware in the reagent path.
Solution Approach 2:
The patent creates a virtual model of dosing system performance using pressure data rather than direct flow measurement. By monitoring pressure differentials and comparing them to expected values, the system replicates the diagnostic capability that would require physical flow meters, but using simpler and less expensive pressure sensing technology.
3Manufacturing precision
If pressure feedback control is maintained during dosing to ensure stable reagent delivery, then dosing accuracy is improved, but the ability to perform diagnostic pressure drop measurements is reduced
Solution Approach 1:
The patent implements periodic diagnostic measurements during the dosing cycle. Pressure feedback control operates continuously for dosing accuracy, but the system periodically suspends it to perform diagnostic pressure drop measurements. This periodic interruption allows the system to gather diagnostic data without compromising overall dosing performance, as the interruptions are brief and occur during normal operation cycles.
Solution Approach 2:
The patent performs diagnostic measurements at specific predetermined points in the dosing cycle where pressure feedback suspension has minimal impact on overall dosing accuracy. By selecting optimal timing for diagnostic interruptions, the system ensures that fault detection capability is maintained while preserving dosing precision during the majority of the dosing period.
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 method effectively identifies dosing system failures, ensuring consistent reagent supply to the SCR catalyst, reducing false alarms and maintenance costs while maintaining NOx emission treatment performance.
Implementation Method 1
measuring a pressure drop of the dosing system downstream of the pump during the doser on-time
Data Source
AI summary
Systems and methods are disclosed for determining or diagnosing a reagent dosing system failure to provide sufficient reagent to an exhaust aftertreatment system that includes an SCR catalyst to satisfy a reagent dosing command.