Passive NOx Adsorption for SCR Cold Start Management
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Solution Overview
Problem
Selective catalytic reduction (SCR) catalysts face inefficiencies in low temperature conditions, leading to ineffective NOx reduction and reductant deposition, which degrades performance and increases fuel consumption due to the need for thermal management.
Innovation Solution
The implementation of a passive NOx adsorption system that stores NOx emissions at low temperatures and releases them when the SCR catalyst is within an effective temperature range, combined with a reductant injector system that delays reductant dosing until higher temperatures are reached, optimizing NOx conversion efficiency and reducing reductant deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reductant is dosed into the exhaust flow upstream of the SCR catalyst during cold start and low temperature conditions, then NOx reduction is attempted, but reductant deposits form on the catalyst which degrades performance and increases back pressure
Solution Approach 1:
The system performs preliminary thermal management of the exhaust flow to raise the temperature to a threshold level before reductant dosing is activated. This preliminary heating action prevents the harmful effect of reductant deposition by ensuring the catalyst is at an adequate temperature to process the reductant effectively, thereby maintaining NOx reduction performance without deposit formation.
2Reliability
If thermal management strategies are used to increase exhaust temperatures to effective operating range, then SCR catalyst performance is improved, but fuel economy deteriorates due to additional fuel consumption
Solution Approach 1:
The system applies thermal management partially, only to the extent necessary to reach the minimum threshold temperature required for effective SCR operation. Rather than continuously maintaining high temperatures, the system provides just enough thermal energy to enable catalyst functionality, thereby improving SCR effectiveness while minimizing the fuel economy penalty associated with excessive thermal management.
3Adaptability or versatility
If SCR catalyst operates at low temperatures, then the system can function during cold start conditions, but NOx conversion efficiency is insufficient to meet emissions standards
Solution Approach 1:
The system applies preliminary thermal management action to counteract the adverse effect of low temperature on SCR catalyst performance. By pre-heating the exhaust flow to a threshold temperature before SCR dosing begins, the system prevents the catalyst from operating in the inefficient low-temperature range, thereby ensuring adequate NOx conversion efficiency while maintaining the ability to function during cold start conditions.
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 enhances NOx conversion efficiency, reduces fuel consumption by eliminating the need for thermal management strategies, and ensures compliance with emissions standards by managing NOx emissions effectively across a wider temperature range.
Implementation Method 1
passive NOx adsorption device...stores NOx emissions at low temperatures and releases them when the SCR catalyst is within an effective temperature range
Implementation Method 2
passive NOx adsorption device...also function for hydrocarbon (HC) and carbon monoxide (CO) conversion, NO oxidation
Data Source
AI summary
Systems and methods for managing aftertreatment systems that include passive NOx adsorption devices and SCR catalyst elements are disclosed. Temperature generation devices upstream of the passive NOx adsorption devices facilitate control of the aftertreatment systems to improve fuel economy and NOx conversion efficiency.