SCR Catalyst Temperature Control via Wastegate and Filter Placement
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Solution Overview
Problem
Vehicle emission control systems face challenges in maintaining SCR catalyst temperature and coordinating emission control devices, particularly due to temperature variations and filter regeneration requirements, which can lead to inefficiencies and performance degradation.
Innovation Solution
The system positions the particulate filter upstream of the turbocharger turbine and the SCR catalyst downstream, with a controller adjusting the turbine wastegate and reductant injection to maintain catalyst temperature and coordinate emission control devices, including EGR and reductant injection, to optimize temperature control and filter regeneration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the filter is positioned upstream of the turbine and regenerated by passing heated exhaust gas through it, then particulate matter is effectively removed, but the SCR catalyst temperature may become uncontrolled and exceed operative ranges
Solution Approach 1:
The exhaust flow is segmented into two paths: one path directs heated exhaust gas through the filter for regeneration, while the other path directs cooler exhaust gas through the turbine to the SCR catalyst. This segmentation allows independent temperature control for each component, enabling effective filter regeneration while maintaining SCR catalyst temperature within operative ranges.
Solution Approach 2:
A control valve is introduced as an intermediary device between the exhaust manifold and the SCR catalyst. This valve regulates the flow of exhaust gas to the SCR catalyst, acting as a mediator that balances the thermal requirements of both the filter regeneration process and the SCR catalyst operation, preventing overheating while ensuring effective regeneration.
2Temperature
If the wastegate flow is increased to maintain catalyst temperature during filter storage, then catalyst temperature control is improved, but turbo lag increases
Solution Approach 1:
The system dynamically adjusts the wastegate position based on real-time operating conditions, including filter regeneration status and SCR catalyst temperature requirements. During filter storage, the wastegate is positioned to maintain optimal catalyst temperature, while during normal operation, it is adjusted to minimize turbo lag and maximize response speed, providing adaptive optimization of both temperature control and performance.
Solution Approach 2:
The control system changes the wastegate opening parameter dynamically based on operational mode. When filter regeneration is not active, the wastegate is opened more to reduce backpressure and improve turbo response. When filter storage is detected or catalyst temperature needs maintenance, the wastegate positioning is adjusted to prioritize temperature control, thereby adapting the parameter to current system needs.
3Reliability
If multiple emission control devices are coordinated through complex control systems, then emission control effectiveness is improved, but system complexity increases
Solution Approach 1:
The control valve serves multiple functions: it regulates exhaust flow to the SCR catalyst for temperature control, manages the balance between filter regeneration and catalyst operation, and compensates for turbo lag. By designing a single multi-functional control component, the system achieves effective coordination of multiple emission control devices without requiring a complex array of separate control systems.
Solution Approach 2:
The control functions for temperature management, filter regeneration coordination, and turbo performance optimization are merged into a unified control strategy centered around the control valve and wastegate system. This integration reduces the number of independent control systems needed, simplifying the overall system architecture while maintaining effective coordination of emission control devices.
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 configuration ensures consistent SCR catalyst temperature during filter regeneration, improves reductant mixing, and reduces turbo lag, while coordinating emission control devices to enhance overall engine performance and reduce emissions.
Implementation Method 1
selective catalytic reduction (SCR) systems to reduce NOx emissions. SCR systems involve injection of a reductant upstream of an SCR catalyst. The reductant, or reductant products, then reacts with exhaust NOx species to create byproducts such as nitrogen and water
Implementation Method 2
particulate filters for removing particulates from exhaust gas
Implementation Method 3
During filter regeneration, heated exhaust gas may be passed through the filter to raise the filter temperature above the normal operating temperature and burn off particulate matter previously stored
Implementation Method 4
an SCR catalyst downstream of an exhaust turbine
Data Source
AI summary
Methods and systems are provided for operating an engine including an SCR catalyst downstream of an exhaust turbine and a particulate filter upstream of the turbine. In one example, the method comprises, adjusting a turbine wastegate to adjust a catalyst temperature to a desired catalyst temperature.