Spark-Ignition Direct Injection Engine Fuel Injection Timing
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Solution Overview
Problem
Spark-ignition direct injection engines with high compression ratios face issues of knock and torque reduction due to low octane fuel, especially when operating within high engine load ranges, where existing solutions like retarding ignition timing compromise thermal efficiency and torque.
Innovation Solution
A spark-ignition direct injection engine system that adjusts fuel injection timing and pressure, and ignition timing based on engine speed and octane number, using high fuel pressure for late-stage injection near compression top dead center to enhance turbulence and mixing, and multi-point ignition for high-speed ranges, thereby avoiding abnormal combustion and maintaining torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If ignition timing is retarded to avoid knock in high compression ratio engines, then knock is suppressed, but torque decreases
Solution Approach 1:
The invention changes the fuel injection timing parameter from conventional early injection to late-stage injection (near or after top dead center), which fundamentally alters the combustion characteristics. This parameter change allows the engine to suppress knock through controlled late combustion rather than retarding ignition timing, thereby maintaining torque while preventing abnormal combustion
Solution Approach 2:
The invention dynamically adjusts the fuel injection timing based on engine operating conditions, specifically implementing different injection strategies for different engine speeds and loads. By making the injection timing adaptive rather than fixed, the system can optimize combustion phasing to prevent knock while maintaining power output across various operating conditions
2Loss of energy
If high compression ratio is used to improve thermal efficiency, then thermal efficiency increases, but knock occurs more easily in middle and high load ranges
Solution Approach 1:
The invention changes the fundamental parameter of fuel injection timing to occur late in the compression stroke or early in the expansion stroke, which allows high compression ratios to be used without causing knock. The late injection timing ensures that fuel is introduced only when the piston has already compressed the air, creating a controlled combustion environment that maintains high thermal efficiency while preventing premature ignition
Solution Approach 2:
The invention performs preliminary compression of air to high pressures and temperatures before fuel injection occurs. By pre-compressing the air charge to high ratios and then injecting fuel late in the cycle, the system prepares the combustion chamber conditions to achieve high thermal efficiency while the late fuel addition prevents knock by ensuring fuel is present only when compression is complete
3Power
If ignition timing is advanced to increase torque with high octane fuel, then torque increases, but knock control intervention causes torque reduction when low octane fuel is supplied
Solution Approach 1:
The invention changes the fuel injection timing parameter to late-stage injection, which fundamentally alters how the engine responds to different fuel octane numbers. This parameter change makes the combustion process less sensitive to fuel quality variations, allowing the engine to maintain optimal torque across different octane ratings without requiring aggressive knock control interventions that would reduce power
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 effectively prevents abnormal combustion and maintains torque by optimizing fuel injection and ignition timing, even with low octane fuel, while improving thermal efficiency by advancing ignition timing and reducing the need for ignition timing retardation.
Implementation Method 1
enhance turbulence and mixing
Implementation Method 2
ignition plug arranged to be oriented toward the inside of the cylinder and for igniting mixture gas within the cylinder
Implementation Method 3
sets the fuel pressure to be a high fuel pressure of 30 MPa or above
Data Source
AI summary
A spark-ignition direct injection engine is provided. The engine includes an engine body, a fuel injection valve, a fuel pressure setting mechanism, an ignition plug, and a controller. Within a low engine speed operating range of a predetermined high engine load range, the fuel pressure setting mechanism sets a fuel pressure to 30 MPa or above, the fuel injection valve injects fuel between late stage of compression stroke and early stage of expansion stroke, and the ignition plug performs spark-ignition after the fuel injection completes. Within a high engine speed operating range of the high engine load range, the fuel injection valve injects fuel between intake stroke to mid-stage of compression stroke, and the ignition plug performs the spark-ignition. The ignition timing is changed according to an octane number, the changing width of the ignition timing is shorter within the low engine speed range than the high engine speed range.