Compression Ignition Engine Mode Transition via Swirl Control
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Solution Overview
Problem
The challenge lies in maintaining stable combustion and maximizing thermal efficiency in compression ignition engines, particularly when transitioning between different engine modes, as existing technologies face difficulties in ensuring fuel efficiency and reducing NOx emissions due to unstable flame propagation and excessive cooling losses associated with varying swirl flow strengths.
Innovation Solution
The solution involves adjusting the swirl flow strength before mode changes in a compression-ignition engine by using a swirl control valve to stabilize SI combustion, ensuring the swirl flow reaches a predetermined strength before initiating the second mode, thereby maximizing thermal efficiency and fuel efficiency while maintaining NOx emission control through precise air-fuel ratio management and torque adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the flame propagation speed of SI combustion is increased to maximize thermal efficiency, then the in-cylinder temperature can reach the ignition temperature, but the stability of combustion deteriorates when the engine water temperature is low or the intake air temperature is low
Solution Approach 1:
The patent changes the air-fuel ratio parameter from stoichiometric (14.7:1) to lean mixture (25:1 or higher) to enable CI combustion. This parameter change allows the system to achieve high thermal efficiency while reducing NOx emissions, as the lean mixture promotes compressed self-ignition rather than flame propagation
Solution Approach 2:
The patent introduces dynamic control of combustion mode by switching between SI and CI combustion based on operating conditions. The system dynamically adjusts ignition timing, fuel injection timing, and air-fuel ratio to maintain stable combustion across varying engine water temperatures and intake air temperatures, resolving the stability issue at low temperatures
2Loss of energy
If the air-fuel ratio is made leaner than stoichiometric to reduce NOx emissions and improve thermal efficiency, then fuel efficiency is maximized, but the flame propagation of SI combustion becomes unstable when engine water temperature is low or intake air temperature is low
Solution Approach 1:
The patent changes the air-fuel ratio parameter from stoichiometric (14.7:1) to lean mixture (25:1 or higher) to enable CI combustion. This parameter change allows the system to achieve high thermal efficiency while reducing NOx emissions, as the lean mixture promotes compressed self-ignition rather than flame propagation
Solution Approach 2:
The patent introduces dynamic control of combustion mode by switching between SI and CI combustion based on operating conditions. The system dynamically adjusts ignition timing, fuel injection timing, and air-fuel ratio to maintain stable combustion across varying engine water temperatures and intake air temperatures, resolving the stability issue at low temperatures
3Reliability
If the swirl flow strength is increased to stabilize SI combustion, then combustion stability is improved, but cooling losses increase excessively
Solution Approach 1:
The patent changes the combustion mode from SI to CI by adjusting the air-fuel ratio to lean mixture (25:1 or higher). This fundamental parameter change eliminates the need for strong swirl flow, as CI combustion relies on compressed self-ignition rather than flame propagation, thereby reducing cooling losses while maintaining combustion stability
Solution Approach 2:
The patent introduces dynamic control of combustion mode by switching between SI and CI combustion based on operating conditions. The system dynamically adjusts ignition timing, fuel injection timing, and air-fuel ratio to maintain stable combustion across varying engine water temperatures and intake air temperatures, resolving the stability issue at low temperatures
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 seamless mode transitions in compression-ignition engines, enhancing fuel efficiency and thermal efficiency by stabilizing SI combustion and reducing NOx emissions, while minimizing cooling losses and torque shocks.
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 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 a piston during a compression stroke
Implementation Method 3
adjusting the swirl flow strength before mode changes in a compression-ignition engine by using a swirl control valve to stabilize SI combustion
Implementation Method 4
the pressure buildup caused by the generation of heat and flame propagation of SI combustion
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, a swirl control valve, a sensor and a controller. The controller is configured to execute a first mode module, a second mode module, and a changing module to change an engine mode from a first mode to a second mode in response to a change demand. The changing module outputs signals to the throttle valve and the injector in response to the demand so that an air-fuel ratio of mixture gas becomes a stoichiometric air-fuel ratio or a substantially stoichiometric air-fuel ratio, and outputs a signal to the swirl control valve so that an EGR gas amount decreases more than before the demand, and when the EGR gas amount is determined to be decreased to a given amount, the changing module causes the second mode module to start the second mode.