SCR System NOx Setpoint Adjustment via CO2 Integration
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Solution Overview
Problem
Current selective catalytic reduction systems for nitrogen oxides in vehicle exhausts struggle to adapt to real driving conditions, leading to overconsumption of reducing agents and potential exceedance of emission limits under varying operating conditions, especially during real driving emissions tests.
Innovation Solution
A process that adjusts the setpoint of nitrogen oxides injection in the exhaust line based on cumulative carbon dioxide release and vehicle speed over specific distance intervals, allowing for real-time optimization of reducing agent injection to match real driving conditions, thereby reducing overconsumption and ensuring compliance with emission standards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the setpoint of nitrogen oxides is fixed based on nominal control, then the SCR system can operate with a simple control structure, but the system cannot adapt to real driving conditions leading to overconsumption of reducing agent and potential exceedance of emission limits
Solution Approach 1:
The patent implements feedback control by continuously monitoring the cumulative amount of nitrogen oxides at the outlet of the exhaust line and using this information to adjust the setpoint dynamically. The monitoring-control unit receives measurements from NOx sensors and compares them against target values, then adjusts the reducing agent injection rate accordingly. This closed-loop feedback mechanism enables the system to adapt to real driving conditions and prevents both overconsumption and emission exceedance.
Solution Approach 2:
The patent transforms the static, fixed setpoint approach into a dynamic control system where the setpoint is continuously adjusted based on real-time measurements of nitrogen oxide emissions. The system adapts its operating parameters dynamically according to actual driving conditions, exhaust flow rate, and measured emissions, rather than relying on pre-calibrated fixed values. This dynamic adjustment optimizes reducing agent consumption while ensuring compliance with emission limits.
2Reliability
If a fixed setpoint is used for nitrogen oxides removal, then the control system remains simple, but the system fails to account for variations in driving conditions and exhaust characteristics
Solution Approach 1:
The patent employs feedback control where the monitoring-control unit continuously receives measurements of nitrogen oxide emissions from sensors positioned at the outlet of the exhaust line. These measurements are fed back to adjust the setpoint and controlling parameters in real-time, ensuring reliable compliance with emission limits under varying driving conditions. The feedback loop includes comparison of measured values against target values and automatic adjustment of injection rates.
Solution Approach 2:
The patent changes the controlling parameters from fixed nominal values to dynamically adjusted parameters based on real-time measurements. The setpoint of nitrogen oxides mass flow rate is modified as a function of measured emissions, exhaust flow rate, and other operating conditions. This parameter adaptation allows the system to maintain reliability across different driving scenarios without requiring an overly complex control architecture.
3Reliability
If the SCR system uses a large catalyst size with safety margins, then emission compliance is ensured under all conditions, but the device size and cost increase
Solution Approach 1:
The patent replaces the static safety margin approach with dynamic control that adjusts the setpoint and injection rate based on real-time measurements. Instead of oversizing the catalyst to handle worst-case scenarios, the system dynamically adapts its operating parameters to match actual emissions and driving conditions. This allows for optimized catalyst sizing without compromising compliance reliability.
Solution Approach 2:
The patent modifies the controlling parameters of the SCR system, specifically the setpoint of nitrogen oxides mass flow rate and the reducing agent injection rate, as functions of measured emissions and operating conditions. This parameter adaptation enables the catalyst to operate at optimal efficiency across different conditions, reducing the need for excessive safety margins and allowing for more compact catalyst design.
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 optimizes reducing agent usage, reduces catalyst size requirements, and ensures effective nitrogen oxide reduction while meeting stringent emission standards by closely monitoring and adapting to real operating conditions, thereby minimizing the risk of exceeding emission limits.
Implementation Method 1
a selective catalytic reduction (SCR) system is therefore frequently used... The NH3 is stored in an SCR catalyst in order to reduce the NOx that are in the gases discharged by the exhaust line
Implementation Method 2
The liquid reducing agent decomposes to give gaseous ammonia, of chemical formula NH3
Data Source
AI summary
A process for optimizing a depollution of nitrogen oxides from the gases in an engine exhaust line carried out according to a selective catalytic reduction by injection of a quantity of reducing agent into the line makes it possible to monitor a setpoint of the amount of nitrogen oxides per second at the outlet of the line. A readjustment of the setpoint is made at each completion of successive running distance intervals determined by integration of the speed over a time interval that ends as soon as a predetermined target cumulative amount of carbon dioxide released is reached, an amount of nitrogen oxides at the outlet per kilometer traveled being calculated for each interval from a cumulative amount of nitrogen oxides measured at the outlet and compared with a target amount of nitrogen oxides per kilometer for the calculation of a deviation used for the readjustment of the setpoint.