Diesel Exhaust Fluid Volume Estimation During Freezing
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Solution Overview
Problem
Existing methods for estimating the volume of diesel exhaust fluid (DEF) in a tank are inaccurate during cold ambient conditions, leading to potential over-servicing and ineffective operation of the SCR catalyst, due to the reliance on tank geometry-specific transfer functions and the freezing of DEF, which complicates the estimation process.
Innovation Solution
A method using distinct transfer functions for estimating the volume of liquid DEF, where a first function is based on tank geometry during warm conditions and a second function, independent of tank geometry, is used during cold conditions, utilizing a heater to thaw frozen DEF and estimate its volume based on the thawing pattern, allowing for accurate estimation regardless of tank shape and size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a tank geometry-specific transfer function is used to estimate DEF volume during warm conditions, then the estimation is accurate for that specific tank type, but the method becomes inaccurate during cold conditions when DEF freezes
Solution Approach 1:
The patent divides the volume estimation method into two distinct segments: one for warm conditions using tank geometry-specific transfer functions, and another for cold conditions using heater-based thawing patterns. This segmentation allows each method to be optimized for its specific temperature range, resolving the accuracy issue across different conditions.
Solution Approach 2:
The patent implements a dynamic switching mechanism that selects between different estimation methods based on temperature conditions. When DEF freezes, the system transitions from using tank geometry-based functions to using heater-based thawing pattern functions, making the system adaptable to changing environmental conditions.
2Quantity of substance
If a heater is activated to thaw frozen DEF in the tank, then more liquid DEF becomes available for SCR operation, but the volume estimation becomes more complex due to the changing thawing patterns
Solution Approach 1:
The patent changes the estimation parameters from tank geometry dimensions to heater-based thawing patterns. By monitoring how the DEF thaws around the heater over time, the system can estimate volume without needing complex models of the entire tank geometry, simplifying the estimation process while heater is active.
Solution Approach 2:
The heater acts as an intermediary tool that both thaws the frozen DEF and serves as a reference point for volume estimation. By using the heater's known position and thawing characteristics as a mediator, the system can infer the volume of liquid DEF without directly measuring the entire tank contents.
3Productivity
If the tank design is modified to include a depression at the bottom for housing the heater, then thawing efficiency is improved, but the overall tank capacity is reduced and manufacturing costs increase
Solution Approach 1:
The patent prepares the tank bottom in advance with a depression or recess specifically designed to house the heater. This preliminary structural preparation ensures optimal heater placement and contact with the tank bottom for maximum thawing efficiency, while the depression is designed to minimize impact on overall capacity.
Solution Approach 2:
The patent applies a localized structural modification (depression) only at the specific location where the heater needs to be housed, rather than changing the entire tank design. This localized approach improves thawing efficiency at the critical bottom region while minimizing the impact on overall tank capacity and maintaining manufacturing simplicity.
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 estimation of usable DEF volume during freezing conditions, simplifies tank design, reduces unnecessary servicing, and maintains optimal SCR catalyst operation by using a consistent transfer function for DEF thawing across different tank configurations, thereby improving emission reduction.
Implementation Method 1
A heater coupled to the tank may be used to thaw a portion of the frozen DEF into a liquid state
Implementation Method 2
a heater coupled to the tank may be used to thaw a portion of the frozen DEF into a liquid state
Data Source
AI summary
Methods and systems are provided for estimation of a volume of liquid diesel exhaust fluid (DEF) contained within a DEF tank. In one example, a method for the estimation of the volume of liquid DEF in a DEF tank during DEF freezing conditions may include activating a heater contained within the DEF tank, and then switching estimation of the volume of liquid DEF via a first transfer function to estimation of the volume of liquid DEF via a second transfer function.