SCR Catalyst NO/NO2 Ratio Measurement for Reductant Dosing
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Solution Overview
Problem
Existing exhaust aftertreatment systems struggle to accurately distinguish between nitric oxide (NO) and nitrogen dioxide (NO2) in exhaust gas, leading to inefficient management of reductant dosing, which can result in increased NOx emissions or unreacted reductant slip.
Innovation Solution
A system and method that utilizes a dynamic model of the SCR catalyst to determine the concentrations of NO and NO2 individually, allowing precise control of reductant dosing based on these concentrations and the amount of reductant stored in the SCR catalyst, using sensors and a controller to adjust reductant delivery accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If reductant dosing is increased to ensure complete NOx conversion, then NOx emissions are reduced, but unreacted reductant slip increases
Solution Approach 1:
The system implements feedback control by continuously measuring outlet NOx concentration and using it to adjust reductant dosing rates. The controller monitors the actual NOx conversion efficiency and dynamically modifies the reductant injection amount to maintain optimal conversion while minimizing excess reductant slip.
Solution Approach 2:
The system changes the dosing parameter (reductant injection rate) based on real-time operating conditions and measured NOx concentrations. By dynamically adjusting this parameter rather than using fixed dosing rates, the system optimizes the balance between achieving complete NOx conversion and minimizing reductant slip under varying engine operating conditions.
2Loss of energy
If reductant dosing is decreased to minimize reductant slip, then reductant utilization efficiency improves, but NOx conversion completeness deteriorates
Solution Approach 1:
The feedback control system ensures that reductant dosing is precisely adjusted to match the actual NOx conversion requirements. By monitoring outlet NOx concentrations and comparing them against target values, the controller automatically optimizes the reductant injection rate to achieve complete conversion while minimizing waste, thereby improving reductant utilization efficiency.
Solution Approach 2:
The system transitions from static, pre-programmed dosing strategies to dynamic, real-time dosing control. The reductant injection rate continuously adapts to changing engine operating conditions and actual conversion efficiency, ensuring optimal reductant utilization across the entire operating range while preventing both excess slip and incomplete conversion.
3Ease of operation
If outlet NOx concentration is used as the sole control parameter, then control simplicity is maintained, but inability to distinguish between NO and NO2 leads to suboptimal reductant dosing
Solution Approach 1:
The system introduces a dynamic model of the SCR catalyst as an intermediary between the simple outlet NOx measurement and the reductant dosing control. This model uses the measured outlet NOx concentration along with engine operating parameters to estimate the inlet NOx composition (NO and NO2 ratios), enabling more precise dosing decisions while maintaining relative control simplicity.
Solution Approach 2:
The patent replaces the need for complex multi-sensor measurement systems with a computational approach. Instead of using multiple physical sensors to directly measure inlet NO and NO2 concentrations, the system uses a dynamic model that computationally derives this information from outlet measurements and operating conditions, substituting mechanical measurement complexity with algorithmic processing.
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
Enhances the efficiency of reductant utilization, reducing NOx emissions and minimizing reductant slip by optimizing the amount of reductant injected into the exhaust gas, thereby complying with stringent emission standards.
Implementation Method 1
a selective catalytic reduction (SCR) catalyst in exhaust gas-receiving communication with an engine and at least one reductant dosing system structured to provide reductant to the exhaust gas
Data Source
AI summary
A system includes a controller for an exhaust aftertreatment system including a SCR catalyst in exhaust gas-receiving communication with an engine and at least one reductant dosing system structured to provide reductant to the exhaust gas. The controller is structured to determine a ratio of NO to NO2 at or proximate an inlet of the SCR catalyst. The controller is further structured to command the at least one reductant dosing system to increase, decrease, or maintain an amount of reductant provided to the exhaust gas based on comparing the ratio of NO to NO2 to a previous NO to NO2 ratio.