Combustion System Fuel Injection Timing for Knock Suppression
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Solution Overview
Problem
Conventional combustion systems face challenges in effectively suppressing engine knock due to inefficient fuel injection timing, which can weaken airflow and fail to adequately intensify turbulence, leading to inadequate flame propagation and auto-ignition suppression.
Innovation Solution
A combustion system that controls fuel injection to occur within a specific period before the first half of the compression stroke, reducing the specific heat ratio and utilizing vaporization heat to lower the temperature in the combustion chamber, thereby suppressing auto-ignition and knock without relying solely on mid-compression stroke fuel injection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If fuel injection is performed during the compression stroke to suppress knock, then auto-ignition suppression is improved, but airflow intensity and turbulence are weakened
Solution Approach 1:
The injection device performs fuel injection during the intake stroke or early compression stroke (before the first half of compression stroke ends) to preliminarily mix fuel with air and prepare the air-fuel mixture before the period when airflow intensity is critical. This preliminary action allows knock suppression through controlled fuel addition without compromising the main airflow intensity needed for combustion.
Solution Approach 2:
The fuel injection process is segmented into different phases: intake stroke injection for initial mixing, and early compression stroke injection for final mixture preparation. This segmentation allows different injection purposes to be fulfilled at different times, maintaining airflow intensity while achieving auto-ignition suppression.
2Speed
If fuel injection timing is delayed to maintain airflow, then turbulence intensification is improved, but flame propagation becomes inadequate
Solution Approach 1:
Fuel injection is performed preliminarily during the intake stroke or early compression stroke to establish the air-fuel mixture before the period when turbulence intensity is maximized. This ensures that when turbulence peaks, the fuel is already distributed and ready for efficient flame propagation, eliminating the need to delay injection to maintain turbulence.
Solution Approach 2:
The injection timing parameter is optimized to occur before the first half of the compression stroke ends, rather than during mid-compression. This parameter change allows the system to maintain both high turbulence intensity and adequate flame propagation by having fuel ready for combustion when turbulence peaks.
3Object-affected harmful factors
If mid-compression stroke fuel injection is used, then knock suppression is achieved, but heat transfer to air-fuel mixture increases
Solution Approach 1:
Fuel injection is performed preliminarily during the intake stroke or early compression stroke, allowing the fuel to mix with air and undergo vaporization before the period of maximum heat transfer to the combustion chamber walls. This preliminary mixing reduces the temperature of the air-fuel mixture during compression, suppressing knock without requiring mid-compression injection that would increase heat transfer losses.
Solution Approach 2:
The injection timing is optimized to allow fuel vaporization (phase transition from liquid to gas) to occur during the intake stroke or early compression stroke. This phase transition absorbs heat and lowers the temperature of the air-fuel mixture, reducing heat transfer to the combustion chamber walls and suppressing knock without the energy losses associated with mid-compression injection.
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 efficiently reduces the temperature near the compression top dead center, enhances turbulence intensity, and effectively suppresses auto-ignition and knock, improving engine performance by preventing heat transfer to the air-fuel mixture and optimizing fuel distribution.
Implementation Method 1
utilizing vaporization heat to lower the temperature in the combustion chamber, thereby suppressing auto-ignition and knock
Implementation Method 2
controls fuel injection to occur within a specific period before the first half of the compression stroke, reducing the specific heat ratio and utilizing vaporization heat to lower the temperature
Data Source
AI summary
A combustion system is applied to an engine. The combustion system includes an injection device that injects a fuel into a combustion chamber, a spark plug that ignites fuel in the combustion chamber, and a control device that controls the injection device and the spark plug. The control device includes a first control unit that executes predetermined first control. In the first control, control is performed such that, a total injection amount corresponding to all the fuel injected by the injection device in one combustion cycle of the engine is injected within a first period corresponding to a period from valve close timing which brings an intake valve into a closed state until a first half of a compression stroke of the engine ends.