Air-Assist Reductant Dosing System Priming Detection
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Solution Overview
Problem
Conventional reductant dosing systems face challenges with trapped air affecting precision and contamination issues, leading to unpredictable reductant injection and potential clogging, which existing priming and purging methods do not adequately address.
Innovation Solution
A reductant dosing system with a controller that calculates average pressures and initiates priming and purging based on specific pressure drops and elapsed times, ensuring accurate priming and complete purging by regulating air and return valves, and using sensors to determine system functionality and diagnose issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional reductant dosing systems operate without specialized priming and purging control, then the system structure remains simple, but trapped air and contaminants cause dosing precision to deteriorate
Solution Approach 1:
The system performs preliminary priming and purging operations before normal dosing begins. The controller executes a priming sequence that fills passages with reductant and a purging sequence that removes trapped air and contaminants, ensuring the system is ready for precise dosing without requiring complex real-time adjustments during operation
Solution Approach 2:
The system uses pressure sensors to monitor pressure changes in the reductant tank and passages during priming and purging operations. The controller analyzes these pressure feedback signals to determine when priming is complete (when pressure stabilizes at expected levels) and when purging is complete (when pressure drops indicate air removal), automatically controlling the timing of valve operations
2Manufacturing precision
If the return valve is opened for a fixed time period to release trapped air, then the control logic remains simple, but dosing precision deteriorates due to excessive or insufficient priming
Solution Approach 1:
The controller monitors pressure sensor feedback during the priming operation and dynamically adjusts the duration that the return valve remains open. When pressure changes indicate that trapped air has been sufficiently removed and reductant has filled the passages, the controller closes the return valve early, preventing excessive priming. This feedback-based timing ensures optimal priming duration without requiring complex manual control
Solution Approach 2:
The system transitions from static, fixed-time valve control to dynamic, pressure-based valve control. The return valve timing is adjusted in real-time based on pressure feedback, allowing the system to adapt to varying operating conditions and ensure consistent dosing precision across different scenarios
3Reliability
If purging is based on detecting pressure drop, then the detection method remains simple, but reliability deteriorates due to false positives from partially stuck valves or obstructed passages
Solution Approach 1:
The system uses pressure sensor feedback to monitor pressure changes during purging operations. The controller analyzes the pressure drop pattern over time and compares it against expected characteristics to determine when purging is complete. This feedback mechanism allows the system to distinguish between complete purging (expected pressure drop pattern) and partial purging or valve sticking (atypical pressure patterns), improving reliability without complex measurement systems
Solution Approach 2:
The controller performs multiple periodic pressure measurements during the purging sequence and analyzes the pressure drop trend over several measurement cycles. By comparing pressure changes across multiple time points, the system can determine whether the pressure drop indicates complete purging or is due to partial obstruction, reducing false positives while maintaining simple measurement hardware
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
The system ensures precise reductant dosing by effectively removing trapped air and contaminants, improving dosing precision and preventing clogging, while minimizing wasteful or insufficient priming and ensuring thorough purging.
Implementation Method 1
a pressure pump tank (PPT) is filled with compressed air via a first air valve, establishing a certain pressure Pc therein. A return valve is then opened, allowing the compressed air to push reductant out of the PPT and back into a reductant tank
Implementation Method 2
The first air valve is then closed, and a second air valve is then opened to establish the pressure Pc inside a liquid, supply tank (LST). The pressure gradient between the LST and the PPT causes reductant liquid to flow from the LST into the PPT
Implementation Method 3
pumped from the tank into the machine's exhaust system
Implementation Method 4
an air-assist injector. Specifically, the air-assist injector uses pressurized air to atomize and disperse the reductant within outlet passage 18
Data Source
AI summary
A reductant dosing system is disclosed as having a pump, and suction, discharge, and return passages. The system may also have a return valve, an air passage, and an air valve. The system may additionally have an air passage pressure sensor, a discharge passage pressure sensor, and a controller. The controller may be configured to calculate a first average pressure inside the discharge passage while the pump is off, the air valve is open, and the return valve is closed; and calculate a second average pressure inside the discharge passage while the pump is off, the air valve is open, and the return valve is open. The controller may also be configured to determine a pressure drop inside the discharge passage based on the first and second average pressures, and to determine that priming is successful based on the pressure drop and pressures of the discharge and air passages.