Diesel Exhaust Fluid Buffer Tank Freeze Mitigation
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Solution Overview
Problem
Existing diesel exhaust fluid (DEF) systems face challenges in effectively mitigating freezing in buffer tanks, particularly during shutdowns or power outages, which can lead to increased thaw times and potential damage from fluid expansion.
Innovation Solution
The implementation of a DEF system that includes a buffer tank with a solenoid valve controlled by an electronic control module (ECM), which opens during shutdown to drain DEF from the buffer tank to a bulk tank, either partially or fully, based on the remaining DEF level, thereby preventing freezing and reducing thaw time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DEF is stored in a buffer tank during shutdown, then freezing protection is provided, but thaw time increases and fluid expansion damage risk increases
Solution Approach 1:
The system performs preliminary draining of the buffer tank before shutdown or cold weather conditions occur. The control module activates the drain valve to remove DEF from the buffer tank before freezing conditions are encountered, preventing freezing damage and reducing thaw time while maintaining system readiness.
2Reliability
If DEF is completely drained from the buffer tank, then freezing damage is prevented, but immediate use upon restarting is compromised
Solution Approach 1:
The system applies different quality states to different portions of the DEF system. The buffer tank is drained to a controlled level rather than completely emptied, leaving a small residual amount of DEF that prevents freezing damage while providing sufficient fluid for immediate operation upon restart. This localized quality control resolves the contradiction between freezing prevention and immediate usability.
3Ease of operation
If a solenoid valve is used to control DEF draining, then precise control is achieved, but device complexity increases
Solution Approach 1:
The control module autonomously manages the solenoid valve operation based on system conditions. It automatically activates the valve to drain the buffer tank when shutdown or cold weather conditions are detected, and deactivates it when appropriate, eliminating the need for manual intervention and simplifying overall system operation despite the added valve complexity.
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 solution reduces the time required to thaw the DEF, minimizes the risk of freezing and damage from fluid expansion, and ensures efficient operation by maintaining a sufficient DEF level for immediate use upon restarting, even in cold environments.
Implementation Method 1
The drain opening may be a gravity drain that relies on the force of gravity to draw the DEF through the drain opening
Implementation Method 2
The exhaust with the NOx heats the DEF and causes the DEF to break down into ammonia (NH3) and carbon dioxide (CO2)
Implementation Method 3
As the NOx and ammonia pass over the catalyst, the NOx and ammonia react to produce nitrogen (N2) and water
Data Source
AI summary
A diesel exhaust fluid (DEF) system and a method of controlling the DEF system are disclosed. The method may include determining that a shutdown condition of the DEF system is satisfied; providing a control signal to open a valve of a buffer tank of the DEF system based on determining that the shutdown condition of the DEF system is satisfied; determining that a level of DEF remaining in the buffer tank satisfies a threshold; and closing the valve of the buffer tank based on the level of DEF remaining in the buffer tank satisfying the threshold.