Compression Ignition Engine Control System for Mode Transition
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Solution Overview
Problem
The challenge is to maintain exhaust emission performance and thermal efficiency in a compression ignition engine when switching between different air-fuel ratio modes, as existing methods face difficulties in stabilizing combustion and reducing NOx emissions during mode changes.
Innovation Solution
The solution involves a control system that adjusts the fuel amount and ignition timing during mode changes, maintaining a stoichiometric air-fuel ratio to stabilize combustion and reduce NOx emissions, while using a changing module to manage the air-fuel ratio and throttle valve to ensure constant engine torque and efficient combustion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the air-fuel ratio is changed during mode switching, then the combustion mode can be changed between stoichiometric and lean SPCCI combustion, but the exhaust emission performance deteriorates due to NOx generation during the transition period
Solution Approach 1:
The control system performs preliminary actions by adjusting the air-fuel ratio and ignition timing in advance before completing the mode switch. During the transition from stoichiometric to lean mode, the system maintains a stoichiometric air-fuel ratio for a predetermined period after mode change detection, ensuring the three-way catalyst remains within its purification window and preventing NOx emissions during the critical transition phase.
Solution Approach 2:
The system dynamically adjusts multiple parameters including air-fuel ratio, ignition timing, and throttle valve opening based on the engine operating conditions and mode change state. The control strategy transitions from static mode switching to dynamic parameter adjustment, where the air-fuel ratio is temporarily held at stoichiometric levels during mode change to maintain emission performance while the combustion mode transitions.
2Stability of the object's composition
If the fuel amount is increased to maintain stoichiometric air-fuel ratio during mode change, then combustion stability is improved, but the engine torque increases excessively
Solution Approach 1:
The control system changes multiple parameters simultaneously to achieve the desired outcome. When increasing fuel amount to maintain stoichiometric air-fuel ratio during mode change, the system concurrently adjusts ignition timing (retarding it appropriately) and throttle valve opening to control the engine torque output, preventing excessive torque increase while maintaining combustion stability.
Solution Approach 2:
The system uses feedback control by monitoring the actual engine torque and air-fuel ratio during mode change, and adjusting the fuel injection amount, ignition timing, and throttle valve opening accordingly. This closed-loop control ensures that combustion stability is maintained while preventing excessive torque increase through real-time parameter adjustments.
3Power
If the ignition timing is retarded to control torque during mode change, then engine torque is controlled, but the combustion efficiency decreases
Solution Approach 1:
The system dynamically adjusts ignition timing based on the engine operating conditions and mode change state. Rather than using a fixed retarded ignition timing, the control system optimizes the ignition timing in real-time, retarding it only to the extent necessary for torque control while minimizing the impact on combustion efficiency. The ignition timing is continuously adjusted as the mode change progresses and operating conditions evolve.
Solution Approach 2:
The control system compensates for the torque-reducing effect of retarded ignition timing by adjusting other parameters such as fuel injection amount and throttle valve opening. By coordinating changes in multiple parameters, the system achieves torque control while minimizing the negative impact on combustion efficiency through optimized parameter combinations.
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 prevents a reduction in exhaust emission performance and maintains thermal efficiency by stabilizing combustion and reducing NOx emissions during mode changes, ensuring the engine operates within a purification window for the three-way catalyst.
Implementation Method 1
combustion by compressed self-ignition in which a mixture gas combusts at once without flame propagation being intervened
Implementation Method 2
The CI combustion is combustion started by the mixture gas inside the combustion chamber carrying out compressed self-ignition
Implementation Method 3
The in-cylinder temperature increases according to an increase in the in-cylinder pressure. The in-cylinder pressure during SPCCI combustion is a result of two pressure buildups comprised of a pressure buildup by a compression work of the piston during a compression stroke
Implementation Method 4
NO x contained in exhaust gas can be purified using a three-way catalyst attached to the exhaust passage
Data Source
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AI summary
A control system for a compression ignition engine is provided, which includes a combustion chamber, a throttle valve, an injector, an ignition plug, a sensor, and a controller. A changing module of the controller outputs a signal to the throttle valve so that an air amount increases more than before a demand of changing from a first mode to a second mode, and outputs to the injector a signal to increase a fuel amount according to the air amount increase so that an air-fuel ratio of mixture gas becomes at or substantially at a stoichiometric air-fuel ratio, and outputs to the ignition plug a signal to retard an ignition timing so that an engine torque increase caused by the fuel amount increase is reduced. The changing module reduces the retarding of the ignition timing when the ignition timing is determined to have reached a retard limit.