Exhaust NOx Sensor Correction for Precise Reducing Agent Dosage
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Solution Overview
Problem
Current methods for controlling the dosage of reducing agents in exhaust streams to reduce nitrogen oxides in combustion engines are not precise due to inaccurate nitrogen oxides sensors, leading to suboptimal performance, increased fuel consumption, and potential residues that affect the efficiency of the exhaust treatment system.
Innovation Solution
A method that determines a sensor correction value by assuming the exhaust stream is free from nitrogen oxides, allowing for an adjusted sensor signal to be used for closed-loop control, reducing sensor offset errors and improving the accuracy of reducing agent dosage, thereby optimizing nitrogen oxides reduction and reducing fuel consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional nitrogen oxides sensors are used for closed-loop control of reducing agent injection, then the system can operate with simple sensor hardware, but the measurement precision is insufficient leading to inaccurate dosage control
Solution Approach 1:
The patent introduces an intermediary correction mechanism that mediates between the imperfect sensor measurement and the required control accuracy. A correction value is calculated based on the difference between measured nitrogen oxides levels and expected levels from a reference map, and this correction value adjusts the sensor signal to compensate for measurement errors without requiring hardware changes.
Solution Approach 2:
The patent replaces the need for high-precision physical sensor hardware with a computational correction system. Instead of improving the physical sensor's measurement capability, the system uses software-based correction algorithms to substitute for the missing measurement precision, achieving accurate control through information processing rather than mechanical improvement.
2Reliability
If higher dosage of reducing agent is injected to compensate for sensor inaccuracies, then nitrogen oxides reduction effectiveness improves, but fuel consumption increases and residues form in the exhaust system
Solution Approach 1:
The patent implements a feedback mechanism where the measured nitrogen oxides levels are continuously compared against expected values from a reference map. The correction value is calculated based on this feedback loop, allowing the system to adjust the reducing agent dosage precisely to match actual needs rather than using excessive amounts, thereby maintaining effectiveness while reducing energy loss.
Solution Approach 2:
The patent changes the parameter used for control from raw sensor signal to corrected sensor signal. By transforming the control parameter through the correction algorithm, the system achieves more accurate dosage control that prevents both under-dosing (ineffective reduction) and over-dosing (wasted fuel and residue formation).
3Manufacturing precision
If sensor correction values are calculated and applied to adjust sensor signals, then dosage control precision improves, but the control system complexity increases
Solution Approach 1:
The patent introduces an intermediary correction mechanism that mediates between the imperfect sensor measurement and the required control accuracy. A correction value is calculated based on the difference between measured nitrogen oxides levels and expected levels from a reference map, and this correction value adjusts the sensor signal to compensate for measurement errors without requiring hardware changes.
Solution Approach 2:
The system performs self-correction using its own measurement data and a reference map. The correction mechanism is self-contained, using the sensor's own output combined with pre-stored reference information to generate the correction value, eliminating the need for external calibration equipment or complex additional sensing systems.
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 precise control of reducing agent injection, enhancing the efficiency of nitrogen oxides reduction, improving the stability of the exhaust treatment system, and meeting stricter emission standards like Euro IV, Euro V, and Euro VI, while also optimizing fuel efficiency.
Implementation Method 1
a redox-reaction may occur between nitrogen oxides NOx in the exhausts and ammonia NH3 available via the additive/reducing agent
Data Source
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AI summary
A method, a system, a computer program and a computer-readable medium for control of dosage of a reducing agent into an exhaust stream from an engine are disclosed. The method method includes: - determining at least one sensor signal SNOx from at least one nitrogen oxides N0x sensor arranged downstream of at least one of the one or more reduction catalysts as at least one sensor correction value SNOx corr, respectively, if: - the engine revolves without fuel supply; - an exhaust mass flow Mexh is greater than an exhaust mass flow threshold Mexh th; Mexh>Mexh th; and - the at least one sensor signal SNOx has had a value smaller than a sensor signal threshold SNOx th; SNOx<SNOx th; during at least a predetermined time period Tcon; - determining at least one adjusted sensor signal SNOx adj based on the at least one sensor signal SNOx and the at least one sensor correction value SNOx corr, respectively; and - controlling the dosage of the reducing agent based on the at least one adjusted sensor signal SNOx adj .