Spark-Ignition Engine Control for Combustion Stability
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Solution Overview
Problem
Spark-ignition gasoline engines face challenges in maintaining combustion stability and reducing pumping loss, especially when switching between compression-ignition and spark-ignition modes, particularly at middle engine loads where fuel amounts are small and air intake needs to be reduced.
Innovation Solution
A control device that adjusts fuel injection timing and pressure, using a high fuel pressure injection during the retard period from late compression to early expansion stroke, and implements external EGR control to introduce a larger amount of EGR gas, thereby stabilizing combustion and reducing pumping loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If external EGR control is added to reduce pumping loss in spark-ignition combustion, then pumping loss is reduced, but combustion stability deteriorates
Solution Approach 1:
The patent changes the fuel injection timing parameter to near top dead center (TDC) and increases fuel pressure to achieve ultra-rapid combustion. This parameter change allows for more aggressive EGR rates without compromising combustion stability, as the shortened combustion duration better utilizes the available combustion chamber volume and reduces the negative impact of EGR on flame propagation.
Solution Approach 2:
The patent implements dynamic control of fuel injection pressure and timing based on operating conditions. By dynamically adjusting injection parameters, the system maintains optimal combustion stability across varying loads while enabling higher EGR rates, particularly in the critical transition zone around middle engine load.
2Power
If fuel amount is reduced at middle engine load near the boundary between compression-ignition and spark-ignition modes, then engine load is reduced, but the ability to reduce intake air charging amount is limited
Solution Approach 1:
The patent applies parameter changes by increasing fuel pressure and adjusting injection timing to achieve more complete and rapid fuel combustion. This allows the engine to maintain stable spark-ignition combustion at lower fuel amounts, enabling greater EGR introduction and thereby reducing the need for intake air charging reduction even when operating at middle engine loads with smaller fuel amounts.
3Loss of energy
If compression-ignition combustion is performed at high engine load, then thermal efficiency is improved, but abnormal combustion such as knocking occurs
Solution Approach 1:
The patent employs dynamic control of combustion mode selection based on real-time engine operating conditions. The system transitions from compression-ignition to spark-ignition combustion as engine load increases, and further utilizes controlled EGR introduction and optimized fuel injection parameters to maintain stable combustion and prevent knocking at high loads where spark-ignition is used.
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 shortens the combustion period, improves stability, reduces pumping loss, and allows for increased EGR introduction without air intake reduction, enhancing thermal efficiency and emission performance.
Implementation Method 1
a fuel pressure variable mechanism for changing a pressure of the fuel that is injected by the fuel injection valve
Implementation Method 2
an ignition plug arranged to be oriented inside the cylinder and for igniting air-fuel mixture within the cylinder
Implementation Method 3
a compression-ignition combustion is performed and a spark-ignition combustion is performed
Implementation Method 4
the introduction of the external EGR is advantageous in reducing cooling loss as well as beneficial in avoiding the abnormal combustion
Data Source
AI summary
A control device of a spark-ignition gasoline engine is provided. The control device includes a controller for operating the engine body by controlling at least a fuel injection valve, an ignition plug, and a fuel pressure variable mechanism. Depending on the engine load range, the controller sets the combustion mode to a compression-ignition mode or a spark-ignition mode. In each mode, the controller also controls the fuel pressure, and the timing of fuel injection and ignition. The controller may also performs external EGR control in each mode.