SCR Catalyst Modeling for NO and NO2-Based 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) concentrations in exhaust gas, leading to inefficiencies in reductant delivery and potential reductant slip due to the inability of NOx sensors to differentiate between these gases.
Innovation Solution
A system and method for determining individual concentrations of NO and NO2 using a dynamic model of the SCR catalyst, combined with sensor data, to optimize reductant dosing based on these concentrations and the amount of stored reductant in the catalyst.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If NOx sensors are used to measure exhaust gas composition, then NOx concentration can be detected, but the sensors cannot differentiate between NO and NO2 leading to imprecise measurement
Solution Approach 1:
The patent introduces a dynamic model of the SCR catalyst as an intermediary computational tool that processes the combined NOx measurement along with other sensor data (oxygen sensors, temperature sensors, flow meters) to mathematically differentiate and estimate individual NO and NO2 concentrations. This mediator translates the limited sensor data into precise gas species differentiation through catalytic reaction modeling.
Solution Approach 2:
The patent replaces the need for complex physical measurement systems (such as multiple specialized gas sensors or mass spectrometers) with a computational approach using a dynamic mathematical model. This model substitution uses readily available sensor data combined with catalytic reaction kinetics to achieve precise gas species differentiation that would be difficult and expensive to obtain through purely mechanical sensing means.
2Reliability
If reductant dosing is increased to ensure complete NOx conversion, then NOx emission reduction is improved, but reductant slip increases causing waste and potential harmful emissions
Solution Approach 1:
The patent implements a feedback control system where the dynamic model continuously estimates actual NO and NO2 concentrations based on sensor measurements and catalyst state. This estimated information feeds back to the reductant dosing system, allowing real-time adjustment of reductant injection rates to match the actual NOx conversion needs, thereby preventing both insufficient dosing (which would compromise NOx reduction) and excessive dosing (which would cause reductant slip).
Solution Approach 2:
The patent dynamically changes reductant dosing parameters (injection rate, timing, and distribution) based on real-time estimates of NO and NO2 concentrations from the dynamic model. By adjusting these parameters according to the actual gas composition and catalyst state, the system optimizes reductant utilization to achieve complete NOx conversion while minimizing reductant slip and waste.
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 precision of reductant delivery, reducing reductant slip and improving the effectiveness of NOx conversion in exhaust aftertreatment systems by ensuring optimal reductant usage.
Implementation Method 1
a selective catalytic reduction (SCR) catalyst in exhaust gas-receiving communication with an engine
Data Source
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AI summary
Systems, apparatuses, and methods include 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 concentration of one or more of NO and NO2 at or proximate an inlet of the exhaust aftertreatment system and based on a dynamic model of the SCR catalyst, information indicative of a concentration of NOx at or proximate an outlet of the exhaust aftertreatment system, and information indicative of an amount of stored reductant in the SCR catalyst. The controller is further structured to command the at least one reductant doser to increase, decrease, or maintain an amount of reductant provided to the exhaust gas based on the determined concentration of one or more of NO and NO2 in the exhaust gas.