Combustion System Knock Suppression via Multi-Stage Fuel Injection
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Solution Overview
Problem
Conventional lean burn combustion systems face challenges in precisely suppressing engine knock, especially during high engine revolutions, due to difficulties in controlling fuel distribution and flame propagation in the combustion chamber.
Innovation Solution
A combustion system with an injection apparatus and ignition plug that performs main and sub-injections in specific phases of the compression stroke to create a rich air-fuel ratio near the ignition plug, while maintaining a lean air-fuel ratio in the exhaust-side region, facilitating flame propagation to a delay region where self-ignition occurs, thereby suppressing knock.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If lean burn combustion is used to reduce emissions, then exhaust emission is improved, but engine knock occurs more easily during high engine revolutions
Solution Approach 1:
The patent applies local quality by creating different air-fuel ratio distributions in different regions of the combustion chamber. Specifically, a rich air-fuel ratio is formed in the ignition plug vicinity to prevent knock, while maintaining a lean air-fuel ratio in the exhaust-side region to reduce emissions. This spatial differentiation of mixture composition allows simultaneous achievement of knock suppression and emission reduction.
Solution Approach 2:
The patent segments the fuel injection process into multiple injection events (main injection and sub-injection) occurring at different timings. The main injection occurs in the intake stroke to establish the overall lean mixture, while the sub-injection occurs in the compression stroke to create a rich zone near the ignition plug. This temporal and spatial segmentation enables precise control of local mixture properties.
2Device complexity
If fuel distribution is not precisely controlled, then device complexity is reduced, but flame propagation control becomes difficult leading to knock
Solution Approach 1:
The patent applies preliminary action by performing sub-injection during the compression stroke before the main ignition event. This preliminary fuel injection creates a rich air-fuel ratio mixture in the ignition plug vicinity in advance, ensuring that when ignition occurs, the flame propagation is controlled and knock is suppressed. The preliminary action prepares the combustion chamber conditions needed for reliable knock prevention.
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 precise control of fuel distribution and effective suppression of engine knock, reducing torque reduction and emissions while maintaining a high torque output and within allowable exhaust emission thresholds.
Implementation Method 1
an injection apparatus configured to inject fuel into a combustion chamber of an engine
Implementation Method 2
an ignition plug configured to perform ignition on the fuel in the combustion chamber
Implementation Method 3
facilitating flame propagation to a delay region where self-ignition occurs
Data Source
AI summary
A normal control unit performs a normal control to cause an injection apparatus to perform predetermined normal injection and subsequently cause an ignition plug to perform ignition. In a delay region in a combustion chamber, propagation of flame is retarded further than in another region when the normal control is performed. In a knock state, self-ignition occurs in the delay region when the normal control is performed. When the knock state is established, an adjustment control unit performs, to suppress the self-ignition, an adjustment control to perform main injection and subsequently perform sub-injection in a second half of a compression stroke to adjust a fuel distribution in the combustion chamber to facilitate propagation of flame to the delay region further than in the normal control and subsequently cause the ignition plug to perform the ignition.