SCR Catalyst EGR Adjustment for Fuel Economy
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Solution Overview
Problem
Engine adjustments that improve fuel economy often increase engine emissions, and increasing exhaust gas recirculation (EGR) to reduce NOx emissions can decrease fuel economy, making it challenging to balance emissions and fuel efficiency.
Innovation Solution
Adjusting the EGR amount supplied to the engine based on the efficiency of the selective catalyst reduction (SCR) catalyst, specifically by decreasing EGR when SCR efficiency is high and limiting urea injection to extend urea tank refill intervals, while maintaining desired emissions levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If EGR amount is increased to reduce NOx emissions, then tailpipe NOx emissions are reduced, but fuel economy decreases
Solution Approach 1:
The system dynamically adjusts EGR amount based on real-time SCR catalyst efficiency and NH3 storage levels. When SCR efficiency is high and NH3 storage is sufficient, EGR is reduced to improve fuel economy. When SCR efficiency drops or NH3 storage is low, EGR is increased to maintain emissions compliance. This dynamic adjustment resolves the contradiction by making EGR a variable parameter rather than a fixed value.
Solution Approach 2:
The control system uses feedback from NH3 storage level sensors and SCR efficiency measurements to continuously adjust EGR amount. The feedback loop monitors the state of the SCR catalyst and modifies engine operation accordingly, allowing the system to optimize the trade-off between emissions control and fuel economy based on actual catalyst performance.
2Object-generated harmful factors
If urea injection is increased to maintain emissions levels with reduced EGR, then tailpipe NOx emissions are controlled, but urea consumption increases and tank refill frequency increases
Solution Approach 1:
The system performs preliminary actions by building up NH3 storage in the SCR catalyst during periods of high SCR efficiency before reducing EGR. This advance preparation of NH3 storage allows the system to later reduce both EGR and urea injection while maintaining emissions control, thereby extending urea tank refill intervals.
Solution Approach 2:
The system changes operational parameters by adjusting EGR amount and urea injection rate based on SCR catalyst state. When SCR efficiency is high, the system transitions to a mode with lower EGR and reduced urea consumption. When SCR efficiency decreases, the system transitions back to higher EGR and normal urea injection, optimizing the balance between emissions control and urea usage.
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 improves fuel economy while maintaining low tailpipe emissions and extending urea tank refill intervals by optimizing engine operations during high SCR efficiency conditions.
Implementation Method 1
a SCR positioned in an engine exhaust system processing exhaust gas can reduce feedgas NOx
Implementation Method 2
process engine exhaust with a selective catalyst reduction system (SCR)
Implementation Method 3
an amount of NH3 stored within a SCR catalyst
Data Source
AI summary
Methods and systems for increasing fuel economy of a vehicle including a SCR catalyst are presented. In one example, an amount of EGR provided to an engine is decreased in response to performance of the SCR being within a predetermined range of performance. The methods and systems may increase vehicle fuel economy while vehicle tailpipe emissions are achieved.