Engine EGR Control Combustion Stability
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Solution Overview
Problem
The existing engine systems face instability in combustion due to excessive exhaust gas recirculation when the swirl control valve switches from fully closed to fully open, leading to an increase in the total amount of exhaust gas introduced into the cylinder, which degrades combustion stability.
Innovation Solution
The controller adjusts the EGR gas amount by increasing it in the low load range and keeping it constant near the load threshold, and reducing it in the high load range, while also controlling fuel injection strategies to maintain combustion stability and improve engine output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the SCV is controlled to fully open in the high load range, then the engine output is improved, but the total amount of exhaust gas introduced into the cylinder increases excessively, degrading combustion stability
Solution Approach 1:
The controller preliminarily adjusts the EGR valve opening before the SCV switches from closed to open state. By detecting the switchable state of the SCV, the system proactively reduces the EGR valve opening in advance, preventing excessive exhaust gas accumulation that would occur if the EGR valve remained fully open during the transition period.
Solution Approach 2:
The system dynamically adjusts the EGR valve opening based on the real-time state of the SCV. When the SCV is in the process of switching from closed to open, the controller continuously monitors and adjusts the EGR valve position, transitioning it from a high opening (for reduced pumping loss) to a lower opening (to prevent excessive EGR gas) as needed.
2Loss of energy
If the EGR gas amount is increased in the low load range, then the pumping loss is reduced, but the total amount of exhaust gas introduced into the cylinder becomes excessive during SCV switching, degrading combustion stability
Solution Approach 1:
The controller preliminarily adjusts the EGR valve opening before the SCV switches from closed to open state. By detecting the switchable state of the SCV, the system proactively reduces the EGR valve opening in advance, preventing excessive exhaust gas accumulation that would occur if the EGR valve remained fully open during the transition period.
Solution Approach 2:
The system dynamically adjusts the EGR valve opening based on the real-time state of the SCV. When the SCV is in the process of switching from closed to open, the controller continuously monitors and adjusts the EGR valve position, transitioning it from a high opening (for reduced pumping loss) to a lower opening (to prevent excessive EGR gas) as needed.
3Productivity
If the SCV is switched from fully closed to fully opened, then the intake air flow is improved, but the blown back amount of exhaust gas increases, increasing the amount of exhaust gas introduced into the cylinder
Solution Approach 1:
The controller preliminarily adjusts the EGR valve opening before the SCV switches from closed to open state. By detecting the switchable state of the SCV, the system proactively reduces the EGR valve opening in advance, preventing excessive exhaust gas accumulation that would occur if the EGR valve remained fully open during the transition period.
Solution Approach 2:
The system dynamically adjusts the EGR valve opening based on the real-time state of the SCV. When the SCV is in the process of switching from closed to open, the controller continuously monitors and adjusts the EGR valve position, transitioning it from a high opening (for reduced pumping loss) to a lower opening (to prevent excessive EGR gas) as needed.
Data Source
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AI summary
An engine system is provided, which includes an engine, a swirl control valve, an EGR passage, an EGR gas adjusting mechanism, and a controller. The engine includes a cylinder, a piston, and a fuel injection valve. The swirl control valve is provided inside an intake passage and generates a swirl flow inside the cylinder when it closes. When an engine load is at or below a given threshold, the controller controls the swirl control valve to close. While the engine load is the threshold or below, the controller controls the EGR gas adjusting mechanism such that, at a fixed engine speed, an increase rate of an EGR gas amount with respect to an increase in the engine load is lower in a first load range than in a second load range, the first load range being on a higher load side of the second load range and including the threshold.