EGR Throttle Control Sequence for Spark-Ignition Engine Stability
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Solution Overview
Problem
Supercharged spark ignition engines with partial exhaust gas recirculation circuits face issues with engine stalling, catalyst reliability, and increased pollutant emissions when the driver lifts their foot off the accelerator, due to the longer transfer time of recycled exhaust gases leading to combustion instability and imbalance between fresh air and recycled gases.
Innovation Solution
A method that involves initially keeping the throttle body open while closing the EGR valve and cutting off fuel injection, followed by almost complete closure of the throttle body after a predetermined duration matching the transfer time of recycled gases, ensuring balanced gas evacuation and preventing sudden fuel cutoff in all cylinders.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the EGR valve and throttle body are closed simultaneously when the driver lifts off the accelerator, then the engine torque is reduced to zero quickly, but the recirculated gases remain in the cylinders causing combustion instability and engine stalling
Solution Approach 1:
The throttle body is closed before the EGR valve to preliminarily establish the pressure conditions necessary for stable combustion. This preliminary action ensures that when the EGR valve closes subsequently, the combustion chambers are already prepared to handle the recirculated gases without causing instability or stalling.
Solution Approach 2:
By closing the throttle body first, the system creates a cushioning effect that maintains positive pressure in the intake manifold during the transition phase. This cushioning prevents the pressure drop that would otherwise occur when the EGR valve closes, thereby preventing combustion instability and engine stalling.
2Productivity
If the throttle body is closed immediately when the EGR valve closes, then the gas flow is controlled quickly, but the imbalance between fresh air and recirculated gases increases causing abnormal combustion spikes
Solution Approach 1:
The throttle body is closed in advance before the EGR valve to preliminarily adjust the gas flow dynamics. This ensures that when the EGR valve closes, the intake manifold is already in a state that facilitates balanced gas composition, preventing abnormal combustion spikes.
Solution Approach 2:
Closing the throttle body first creates a cushioning effect that maintains pressure balance in the intake system. This cushioning prevents the sudden pressure drop that would disrupt the balance between fresh air and recirculated gases, thereby preventing combustion instability.
3Use of energy by moving object
If fuel injection is cut off immediately when the accelerator is released, then fuel consumption is reduced, but the engine may stall due to combustion instability
Solution Approach 1:
The throttle body is closed before fuel injection is cut off to preliminarily prepare the combustion chambers for zero-torque operation. This preliminary action ensures that when fuel injection stops, the combustion process remains stable and the engine does not stall.
Solution Approach 2:
Closing the throttle body first creates a cushioning effect that maintains the combustion process stable during the transition to zero torque. This cushioning allows fuel injection to be cut off without causing combustion instability or engine stalling.
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 stabilizes combustion, reduces the risk of engine stalling, maintains catalyst reliability, and minimizes pollutant emissions by managing the transition to zero-torque conditions effectively, addressing the imbalance in gas proportions and transfer times.
Implementation Method 1
supercharged spark-ignition engine
Implementation Method 2
downstream of the turbocharger turbine of the turbocharged engine
Implementation Method 3
downstream of a catalyst for aftertreatment of the engine's combustion gases
Data Source
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AI summary
The invention relates to a method for controlling a supercharged spark-ignition engine associated with a circuit for partial recirculation of exhaust gases to the intake, the engine being mounted on a motor vehicle. The main feature of this method is that, on raising the foot, first the EGR circuit valve closes without changing the position of the throttle valve housing of the engine or opening it further, and the injection of fuel into at least one cylinder of the engine is cut. The throttle valve housing is then almost completely closed after a predetermined period following the closure of the EGR valve, this period corresponding to the transfer time of recycled gases between the EGR valve and the engine.The injection of fuel is cut on the cylinders which, where appropriate, have not been cut before closing of the throttle valve housing. The use of the method is particularly advantageous in the case where the EGR circuit is of the low-pressure type.