NOx Sensor Cross-Sensitivity for Reagent Leakage Detection
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Solution Overview
Problem
Existing methods for operating internal combustion engines with catalytic converters and NOx sensors face challenges in minimizing reagent leakage, leading to unnecessary reagent consumption and odor issues due to the toxicity of ammonia and cross-sensitivity of NOx sensors.
Innovation Solution
The method utilizes the cross-sensitivity of NOx sensors to measure reagent leakage by identifying specific operating states like idling and overrun, where sensor signals primarily reflect reagent leakage, allowing for accurate reagent metering without additional sensors, using a control unit to analyze sensor signals and adjust reagent supply accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the amount of reagent metered is increased to ensure complete reduction of nitrogen oxides, then NOx elimination efficiency is improved, but reagent leakage increases causing unnecessary consumption and odor problems
Solution Approach 1:
The patent employs a feedback mechanism where the NOx sensor continuously monitors nitrogen oxide levels in the exhaust gas and feeds this information back to the control unit. The control unit adjusts the reagent metering rate dynamically based on the sensor signals, ensuring optimal reagent dosage that prevents both insufficient NOx reduction and excessive reagent leakage.
Solution Approach 2:
The system utilizes the cross-sensitivity of the NOx sensor to reagent as a beneficial feature rather than a drawback. The sensor's response to reagent presence serves as an indirect measurement mechanism, allowing the system to self-regulate reagent metering without requiring additional sensors or complex measurement systems.
2Measurement precision
If an additional reagent sensor is installed to directly measure reagent leakage, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent makes the existing NOx sensor perform multiple functions: detecting actual NOx concentrations and simultaneously indicating reagent leakage through its cross-sensitivity response. This multi-functionality eliminates the need for separate reagent sensors, maintaining measurement capability while reducing system complexity.
Solution Approach 2:
The patent converts the harmful cross-sensitivity of the NOx sensor to reagent into a beneficial measurement feature. By utilizing the sensor's unintended response to reagent presence, the system achieves reagent leakage detection without requiring additional hardware, turning a design flaw into a functional advantage.
3Loss of substance
If reagent metering is reduced to minimize leakage and consumption, then reagent cost is reduced, but NOx reduction completeness deteriorates
Solution Approach 1:
The patent implements dynamic reagent metering that continuously adapts to changing engine operating conditions and exhaust gas composition. The control unit adjusts the metering rate in real-time based on sensor feedback, ensuring the system operates at optimal efficiency across varying loads and temperatures, preventing both waste and insufficient treatment.
Solution Approach 2:
The system changes operational parameters dynamically, adjusting reagent metering rate based on engine load, exhaust temperature, and sensor readings. This parameter adaptation allows the system to maintain effective NOx reduction across different operating conditions while minimizing reagent consumption by avoiding excessive metering during low-demand periods.
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 minimizes reagent leakage, optimizing reagent consumption and reducing operational costs while ensuring effective NOx emission reduction, even at varying engine conditions.
Implementation Method 1
The NOx sensors described here have multiple chambers interconnected through the diffusion barriers. The O2 concentration is reduced to a predetermined value in the first chamber by a first electrolytic oxygen pumping cell.
Implementation Method 2
an SCR (selective catalytic reduction) catalytic converter is provided which uses a reagent to reduce nitrogen oxides in the exhaust gas of an internal combustion engine to nitrogen
Implementation Method 3
The O2 concentration is reduced to a predetermined value in the first chamber by a first electrolytic oxygen pumping cell
Data Source
AI summary
A method for operating an internal combustion engine; in the exhaust area of this engine there is at least one catalytic converter and downstream from the catalytic converter there is an NOx sensor. A device for carrying out this method is also provided. The NOx sensor has a cross-sensitivity to a reagent needed in the catalytic converter. In predefined operating states of the internal combustion engine, e.g., idling and/or overrun, a selection signal is supplied; when this selection signal occurs, the sensor signal supplied by the NOx sensor is interpreted as at least a measure of the reagent leakage.