Coordinated HP and LP EGR Control for Engine Transients
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Solution Overview
Problem
Boosted engine systems face challenges with high NOX emissions, poor combustion stability, compressor surge, and delayed catalyst light-off due to the trade-offs between high-pressure (HP) and low-pressure (LP) exhaust gas recirculation (EGR) strategies, which affect engine performance and emissions control, especially during transient conditions.
Innovation Solution
A method to dynamically adjust LP EGR and uncooled HP EGR flow rates within specific limits to maintain target dilution levels in the intake manifold, both at steady-state and transient conditions, allowing for coordinated control of HP and LP EGR to improve engine longevity, fuel economy, and emissions control while enabling rapid response to transients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If high EGR flow rates are used to control NOX emissions, then NOX emissions are reduced, but combustion stability deteriorates and HC/CO emissions increase
Solution Approach 1:
The EGR system is segmented into two separate loops: a high-pressure EGR loop for high-load conditions and a low-pressure EGR loop for low-load conditions. Each loop is optimized for its specific operating range, allowing the system to achieve high EGR flow rates for NOX control when needed while maintaining combustion stability through appropriate loop selection.
Solution Approach 2:
The system dynamically switches between HP EGR and LP EGR modes based on real-time engine operating conditions (load, speed, temperature). This dynamic adaptation allows the system to optimize EGR flow rates for NOX control while maintaining combustion stability by selecting the appropriate EGR mode for the current operating point.
2Object-generated harmful factors
If high EGR flow rates are used to control NOX emissions, then NOX emissions are reduced, but compressor surge becomes more likely
Solution Approach 1:
The EGR system is segmented into two separate loops: a high-pressure EGR loop for high-load conditions and a low-pressure EGR loop for low-load conditions. Each loop is optimized for its specific operating range, allowing the system to achieve high EGR flow rates for NOX control when needed while maintaining combustion stability through appropriate loop selection.
Solution Approach 2:
The system changes the pressure parameter of the EGR flow by selecting between HP and LP modes. This parameter change allows optimization of EGR flow rates for NOX control while maintaining compressor stability through appropriate pressure level selection based on operating conditions.
3Reliability
If LP EGR is used to increase flow through the compressor and prevent surge, then compressor stability is improved, but catalyst warm-up is delayed
Solution Approach 1:
The system dynamically switches between HP EGR and LP EGR modes based on real-time engine operating conditions (load, speed, temperature). This dynamic adaptation allows the system to optimize EGR flow rates for NOX control while maintaining combustion stability by selecting the appropriate EGR mode for the current operating point.
Solution Approach 2:
The system changes the temperature parameter of the EGR flow by selecting between cooled and uncooled modes. This parameter change allows optimization of compressor stability while accelerating catalyst warm-up through appropriate temperature selection based on operating conditions.
4Reliability
If uncooled HP EGR is used to increase manifold air temperature and prevent surge, then compressor stability is improved, but MAT becomes excessively high reducing engine power
Solution Approach 1:
The system changes the temperature parameter of the EGR flow by selecting between cooled and uncooled modes. This parameter change allows optimization of compressor stability while accelerating catalyst warm-up through appropriate temperature selection based on operating 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 engine performance by maintaining combustion stability, preventing compressor surge, and ensuring rapid catalyst warm-up, thereby improving fuel efficiency and reducing emissions.
Implementation Method 1
a charge-air cooler configured to cool the compressed air charge
Implementation Method 2
exhaust-gas recirculation (EGR) is one approach for combating these effects. EGR strategies reduce the oxygen content of the intake air charge by diluting it with exhaust
Data Source
AI summary
A method for charging an intake manifold of an engine comprises adjusting an LP EGR flow rate and an uncooled HP EGR flow rate within first limits to maintain a target dilution level in the intake manifold at steady state. The method further comprises adjusting the LP EGR and uncooled HP EGR rates within second limits, different from the first, to maintain the target dilution level in the intake manifold during transient conditions.