Coordinated EGR and VGT Actuation for Engine Braking
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Solution Overview
Problem
Engine braking techniques often result in decreased catalyst temperature, leading to inefficient emission treatment during vehicle operation, as increased airflow cools the aftertreatment device, thereby increasing emissions upon resuming combustion.
Innovation Solution
Coordinating adjustments of the cross-sectional area of the exhaust turbine inlet and the EGR valve opening to maintain the exhaust system temperature above the light-off temperature during engine braking, by increasing airflow when low braking torque is demanded, minimizing airflow when medium torque is required, and reducing airflow further for high torque demands, using a variable geometry turbocharger and EGR system synergistically.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If airflow through the engine is increased during engine braking, then braking power is increased, but the aftertreatment device temperature decreases rapidly below the light-off temperature
Solution Approach 1:
The patent changes the geometric parameters of the exhaust system by adjusting the VGT vane position to modify the exhaust turbine inlet area, and adjusting the EGR valve opening position, to control exhaust flow and maintain aftertreatment device temperature during engine braking while achieving required braking power
Solution Approach 2:
The patent uses dynamic adjustment of variable geometry components (VGT vanes and EGR valve) during engine braking to continuously optimize the balance between braking power generation and aftertreatment device temperature maintenance
2Power
If the VGT is clamped to produce high engine back pressure for engine braking, then braking power is increased, but airflow through the engine increases leading to rapid cooling of the aftertreatment device
Solution Approach 1:
The patent introduces the EGR valve as an intermediary component to regulate exhaust gas flow and mix hot exhaust gases with incoming air, thereby maintaining aftertreatment device temperature and preventing harmful emissions when the VGT is clamped for engine braking
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 allows for effective emission treatment during engine braking while minimizing catalyst cooling, ensuring efficient emission reduction when combustion is resumed, thereby reducing vehicle emissions.
Implementation Method 1
a variable geometry turbocharger (VGT) may be clamped to produce high engine back pressure
Implementation Method 2
a variable geometry turbocharger (VGT) including a turbine coupled to an exhaust passage of the engine and a compressor coupled to an intake passage of the engine
Implementation Method 3
an exhaust gas recirculation (EGR) system that recirculates exhaust gas to an intake passage of the engine
Implementation Method 4
the catalyst may oxidize hydrocarbons and carbon monoxide and reduce particulate matter
Implementation Method 5
the catalyst may oxidize hydrocarbons and carbon monoxide
Data Source
AI summary
Methods and systems are provided for controlling an EGR valve and VGT vanes during engine braking. In one example, a method may include during an engine braking event in an engine, coordinating adjustments of both of a cross-sectional area of an inlet of a turbine and an opening of a valve of an exhaust gas recirculation (EGR) system to achieve a desired braking power and to maintain an exhaust system temperature above a threshold temperature during the engine braking event.