Liquid Reducing Agent Discrimination via Periodic Thermal Sensing
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Solution Overview
Problem
Conventional exhaust emission purifying apparatuses face challenges in accurately determining the condition of a storage tank containing a liquid reducing agent, particularly when the tank is empty or contains a dissimilar aqueous solution, due to vibration and temperature distribution issues affecting heat transfer characteristics, leading to reduced measurement accuracy.
Innovation Solution
A concentration sensor system with temperature sensors at two positions and a heater is used, where the control unit processes temperature data to discriminate between a filled tank with the correct reducing agent, an empty tank, or a dissimilar solution by setting thresholds and counting frequencies for accurate discrimination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a concentration sensor measuring heat transfer characteristics is used to determine storage tank condition, then measurement capability is provided, but measurement precision deteriorates due to convection caused by vehicle vibration and temperature distribution
Solution Approach 1:
The system performs concentration measurements at predetermined time intervals rather than continuously. The control unit is configured to measure concentration at specific periodic moments, allowing the liquid reducing agent to remain relatively stable between measurements and reducing the impact of convection caused by vehicle vibration and temperature distribution changes.
Solution Approach 2:
The system checks storage tank conditions periodically before actual concentration measurements are taken. By preliminarily determining whether the tank is empty, contains dissimilar solution, or contains normal liquid reducing agent through preliminary assessments, the system can avoid taking measurements when conditions are unfavorable for accurate heat transfer-based concentration determination.
2Reliability
If continuous concentration measurement is performed to ensure accurate NOx purification, then purification performance is maintained, but energy consumption increases due to continuous heater operation
Solution Approach 1:
The concentration sensor's heater operates periodically at predetermined time intervals rather than continuously. This periodic operation reduces energy consumption significantly while still providing sufficient concentration data to maintain accurate NOx purification performance, as the control unit can use these periodic measurements to adjust injection amounts appropriately.
Solution Approach 2:
The control unit uses the concentration measurement data to automatically adjust the liquid reducing agent injection amount, eliminating the need for continuous monitoring. The system serves itself by making injection decisions based on periodic concentration readings, thereby reducing energy consumption while maintaining purification effectiveness.
3Measurement precision
If temperature sensors are placed close together to improve concentration measurement, then measurement sensitivity increases, but temperature distribution uniformity becomes more difficult to maintain under vehicle operation
Solution Approach 1:
By measuring concentration at periodic time intervals rather than continuously, the system allows temperature distribution to stabilize between measurements. The predetermined time intervals are sufficient for temperature uniformity to recover after disturbances from vehicle vibration, enabling accurate measurements with closely spaced temperature sensors without requiring continuous temperature uniformity.
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 enables high-precision discrimination of the storage tank's condition, ensuring accurate NOx purification performance by differentiating between a filled tank with the correct reducing agent, an empty tank, and a tank with a dissimilar solution, even under vehicle vibrations and temperature variations.
Implementation Method 1
a heater incorporated in one of the temperature sensors
Implementation Method 2
indirectly measures the concentration of the liquid reducing agent based on heat transfer characteristics between two positions close to each other
Data Source
AI summary
A discriminating apparatus of liquid reducing agent is disclosed, in which, based on concentration of liquid reducing agent which is measured at each predetermined time after starting of engine, discrimination is processed whether the storage tank is filled with dissimilar aqueous solution, the storage tank is normally filled with the liquid reducing agent, or the storage tank is empty. When the empty discrimination or the dissimilar aqueous solution discrimination is performed, it is judged whether or not the discrimination is adequate according to the liquid condition in the storage tank. When the empty or the dissimilar aqueous solution discrimination is adequate, the empty discrimination frequency or the dissimilar aqueous solution discrimination frequency is counted up. When the empty discrimination frequency and the dissimilar aqueous solution discrimination frequency become equal to or larger than the first predetermined frequency, the discrimination is upheld.