SPCCI Engine Control via Intake Valve Timing
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Solution Overview
Problem
Current engines face challenges in achieving stable partial compression-ignition combustion, particularly under air-fuel lean environments, where combustion start timing is sensitive to external factors and load changes, leading to inefficiencies in thermal efficiency and fuel efficiency.
Innovation Solution
A control system that adjusts the intake valve timing and air-fuel ratio to stabilize spark ignition combustion, allowing for partial compression-ignition combustion across a wide engine speed range by retarding intake valve close timing at low speeds and advancing it at high speeds, while maintaining a lean air-fuel ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the air-fuel ratio is increased to improve fuel efficiency and reduce emissions, then fuel efficiency improves and NOx generation decreases, but flame propagation stability deteriorates and combustion control becomes difficult
Solution Approach 1:
The combustion process is segmented into two distinct phases: SI combustion for a portion of the mixture gas to ensure stable flame propagation, and CI combustion for the remaining mixture gas to achieve high fuel efficiency and low emissions. This segmentation allows each combustion mode to perform its optimal function without the constraints of the other.
Solution Approach 2:
Different regions of the combustion chamber are assigned different combustion modes. The region near the spark plug undergoes SI combustion with stable flame propagation, while other regions undergo CI combustion with self-ignition. This local differentiation allows the system to simultaneously achieve combustion stability and high efficiency.
2Loss of energy
If the in-cylinder temperature is increased to promote CI combustion, then fuel efficiency improves, but the risk of premature combustion and combustion instability increases
Solution Approach 1:
SI combustion is performed as a preliminary action before CI combustion. The spark ignition creates a controlled flame propagation that heats the remaining mixture gas to the appropriate temperature for self-ignition, ensuring that CI combustion occurs at the optimal moment without premature combustion.
Solution Approach 2:
The control device monitors combustion conditions and adjusts the injection timing and amount of fuel for both SI and CI combustion phases. This feedback control ensures that the in-cylinder temperature remains within the optimal range for CI combustion while preventing premature ignition and maintaining combustion stability.
3Loss of energy
If the engine operates in a lean air-fuel environment to improve fuel efficiency, then fuel efficiency improves and NOx emission decreases, but combustion control during transition operations becomes difficult
Solution Approach 1:
The combustion system dynamically switches between SI and CI combustion modes based on operating conditions. During transition operations, the control device adjusts the proportion of SI to CI combustion and modifies injection timing and fuel amounts to maintain stable combustion across varying loads and speeds, enabling excellent adaptability.
4Power
If spark ignition timing is advanced to improve combustion efficiency, then power output increases, but the risk of knock and combustion instability increases
Solution Approach 1:
The ignition process is segmented into spark ignition for controlled flame propagation and self-ignition for the remaining fuel. This segmentation allows the spark timing to be optimized for power output without causing knock, as the CI portion completes the combustion process smoothly without the risk of uncontrolled knock.
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 configuration ensures stable partial compression-ignition combustion, improving fuel efficiency and torque performance by optimizing in-cylinder conditions, reducing NOx generation, and maintaining combustion stability across varying engine loads and speeds.
Implementation Method 1
a spark plug configured to ignite a mixture gas containing the fuel injected by the injector and air
Implementation Method 2
The in-cylinder temperature increases with an increase in an in-cylinder pressure (pressure inside the cylinder). The in-cylinder pressure on the compression stroke when the SPCCI combustion is carried out is increased by compression work of a piston
Implementation Method 3
the remaining mixture gas is combusted by self-ignition (CI combustion)
Data Source
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AI summary
A control system for a compression-ignition engine which performs SPCCI combustion in which mixture gas is ignited with a spark plug to be partially combusted by SI combustion and the rest of mixture gas self-ignites to be combusted by CI combustion, is provided. When the engine is operated at least in a given first operating range, a controller of the device controls an intake variable mechanism so that an A/F lean environment where an air-fuel ratio in a cylinder becomes higher than a stoichiometric air-fuel ratio is formed, while causing the spark plug to perform spark ignition at a given timing so that the mixture gas combusts by SPCCI combustion, and controls so that, under the same engine load condition, an intake valve close timing is more retarded as the engine speed decreases, within a range where an amount of air inside the cylinder decreases by retarding the close timing.