SCR System Control via NOx Sensor Deviation Feedback
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Solution Overview
Problem
Conventional methods for controlling SCR catalytic converters in internal combustion engines face efficiency decreases due to environmental influences, deposits, sulfur poisoning, and sensor inaccuracies, leading to deviations in operating medium injection quantities, which affect NOx conversion rates and reducing agent consumption.
Innovation Solution
A method that adjusts the metering quantity of the operating medium in the SCR system by determining control values through NOx sensor measurements, calculating deviations, and adapting the injection quantity based on predefined ranges, using a urea-containing mixture that converts into ammonia to store reducing agents temporarily in the SCR catalytic converter, thereby optimizing NOx conversion and reducing agent usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional physical models are used to control operating medium injection quantity, then the system can achieve basic emission control, but the SCR efficiency decreases over time due to environmental influences, deposits, and sensor inaccuracies
Solution Approach 1:
The patent implements a feedback mechanism where the actual NOx emissions are continuously measured by an NOx sensor and compared with the modeled NOx emissions. Based on this comparison, the operating medium injection quantity is dynamically adjusted to compensate for efficiency degradation over time. This closed-loop control ensures that the SCR system maintains optimal performance despite aging, environmental influences, and sensor inaccuracies.
2Reliability
If the metering quantity of operating medium is increased to compensate for efficiency loss, then NOx conversion rates can be maintained, but operating medium consumption increases
Solution Approach 1:
The system uses the NOx sensor measurements and mathematical models to automatically determine the optimal injection quantity without requiring external intervention or excessive operating medium addition. The control unit continuously calculates the required adjustment based on the difference between actual and modeled emissions, enabling the system to self-regulate and maintain high conversion efficiency while minimizing operating medium consumption.
3Manufacturing precision
If the metering quantity is adjusted frequently to maintain optimal performance, then emission compliance can be ensured, but the complexity of the control system increases
Solution Approach 1:
The patent adjusts the injection quantity parameter based on changes in the difference between actual and modeled NOx emissions. By monitoring emission parameters over time and calculating the deviation, the system dynamically modifies the operating medium injection rate. This approach maintains precise emission control through parameter adaptation while keeping the control logic relatively simple and transparent.
4Productivity
If sensor measurements are used to determine injection quantity, then real-time control is achieved, but sensor cross-sensitivity to NH3 and environmental influences reduce measurement precision
Solution Approach 1:
The patent introduces a mathematical model as an intermediary between the sensor measurements and the control decision. The model calculates expected NOx emissions based on operating parameters, and this modeled value serves as a reference to interpret the sensor measurements. By comparing actual sensor readings with modeled predictions, the system can distinguish between real emission changes and sensor measurement errors due to cross-sensitivity or environmental influences, thereby improving the accuracy of injection quantity control.
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 method improves the efficiency of the SCR system by stabilizing NOx conversion rates, reducing operating medium consumption, and ensuring compliance with legal emission requirements by accurately adjusting the metering quantity based on real-time emissions data, minimizing inaccuracies from sensor cross-sensitivity and environmental factors.
Implementation Method 1
SCR system for selective catalytic reduction
Implementation Method 2
the reducing agent is stored at least temporarily in an SCR catalytic converter
Implementation Method 3
converted into the reducing agent, in particular NH3, by way of the reactions represented below: Thermolysis: (NH2)2CO→NH3+HNCO
Implementation Method 4
Hydrolysis: HNCO+H2O→NH3+CO2
Implementation Method 5
the reducing agent is stored at least temporarily in an SCR catalytic converter
Data Source
AI summary
The invention relates to a method for improving the efficiency of an SCR system of an exhaust gas aftertreatment system (5) of an internal combustion engine (1), and to an internal combustion engine (1), wherein an operating medium is metered in upstream of the SCR catalytic converter (2) of the SCR system in a normal operating mode, wherein the operating medium comprises a reducing agent or can be converted into a reducing agent, wherein the reducing agent is stored at least temporarily in an SCR catalytic converter (2) of the SCR system, wherein the method comprises the following steps: operating of the internal combustion engine (1) in the normal operating mode, defining of a determined control value (6) by way of determining of the mass of an exhaust gas component which is measured overall at a point in the course of the exhaust gas aftertreatment system (5) during a first measurement window, determining of a calculated control value (7) by way of calculating of the mass of the exhaust gas component which occurs overall at the point in the course of the exhaust gas aftertreatment system (5) during the first measurement window, determining of the deviation (8) between the determined control value and the calculated control value, checking whether the determined deviation lies within a predefined deviation range, adapting of the metering quantity of the operating medium if the determined deviation lies outside the deviation range.