Diesel Exhaust Fluid Stratification Management
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Solution Overview
Problem
Diesel Exhaust Fluid (DEF) stratification due to freezing and thawing in storage tanks leads to inaccurate concentration sensor readings, causing inefficiencies in reductant injection and emission reduction in diesel vehicles.
Innovation Solution
A method that adjusts reductant injection based on concentration sensor readings and vehicle motion to ensure accurate measurement of DEF concentration, using a controller to retrieve valid measurements, determine mixing thresholds, and adjust injection profiles accordingly, thereby ensuring accurate quantification of DEF post-freeze-thaw events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the DEF is stored in a storage tank without mixing mechanisms, then the storage is simple and cost-effective, but the concentration becomes non-uniform due to stratification after freeze-thaw events, leading to inaccurate sensor readings
Solution Approach 1:
The system performs preliminary actions by detecting freeze-thaw events through temperature monitoring and proactively initiating mixing operations before concentration measurements are taken. The controller monitors tank temperature and vehicle motion to determine when mixing is needed, ensuring uniform concentration distribution before the sensor reads the DEF concentration, thereby preventing stratification errors without requiring continuous mixing mechanisms
Solution Approach 2:
The system utilizes vehicle motion itself as the mixing mechanism. When the vehicle moves, the tank experiences sufficient agitation to mix the DEF naturally without requiring separate external mixing devices. The controller detects vehicle motion and determines that the existing vehicle operation provides adequate mixing, eliminating the need for additional mixing hardware in normal operating conditions
2Measurement precision
If the concentration sensor is positioned at a fixed location in the tank, then the installation is simple, but the reading accuracy deteriorates when the tank orientation changes or stratification occurs
Solution Approach 1:
The system performs preliminary mixing actions based on detected freeze-thaw events and vehicle motion before concentration measurements are taken. By ensuring the DEF is uniformly mixed prior to sensing, the fixed-position sensor can accurately measure bulk concentration regardless of tank orientation or previous stratification, maintaining measurement precision without requiring multiple sensor positions or complex positioning mechanisms
3Measurement precision
If the system continuously mixes the DEF in the tank, then the concentration remains uniform and sensor readings are accurate, but the energy consumption and system complexity increase
Solution Approach 1:
Instead of continuous mixing, the system implements periodic mixing actions triggered by detected freeze-thaw events. The controller monitors temperature changes and vehicle motion, initiating mixing only when stratification is likely to have occurred. This periodic approach maintains concentration uniformity and sensor reading accuracy while minimizing energy consumption by activating mixing only when necessary rather than continuously
Solution Approach 2:
The system leverages vehicle motion as a free mixing resource. When the vehicle is in motion, the tank naturally agitates and mixes the DEF without requiring additional energy input. The controller detects vehicle motion and determines that the existing kinetic energy from vehicle operation provides sufficient mixing, eliminating the need for powered mixing mechanisms during normal driving conditions
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 ensures accurate DEF concentration measurement and efficient reductant injection, reducing vehicle emissions by ensuring the DEF is thoroughly mixed before injection, aligning with bulk fluid concentrations.
Implementation Method 1
Vehicle motion may mix the reductant, thereby ensuring an accurate concentration measurement
Implementation Method 2
a urea concentration and level sensor (UCLS) 240...indicate properties of diesel exhaust fluid (DEF) 250 stored within DEF tank 212
Data Source
AI summary
A method for an exhaust system is provided, comprising adjusting reductant injection responsive to a reductant concentration, the reductant concentration based on concentration sensor readings and vehicle motion. If the reductant freezes, the reductant may stratify, leading to inaccurate concentration sensor readings. Vehicle motion may mix the reductant, thereby ensuring an accurate concentration measurement which may then be used to adjust reductant injection.