Multi-Stage Fuel Injection for Spark Ignition Engine Emissions
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Solution Overview
Problem
Conventional spark-ignition direct-injection internal combustion engines face challenges in reducing fuel consumption and pollutant emissions, especially at low loads and cold start conditions, due to inefficient fuel injection methods and catalytic converter heating issues.
Innovation Solution
A method involving multiple fuel injections to create lean and rich fuel/air mixtures, optimized by crank angle and load conditions, ensuring reliable ignition and reduced emissions, with the third injection occurring close to ignition time to maintain smooth engine operation and efficient catalytic converter heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the engine is operated in stratified mode at low loads to reduce fuel consumption, then fuel efficiency is improved, but particle emissions increase drastically
Solution Approach 1:
The fuel injection process is segmented into three distinct injections: a first injection creating a lean background mixture, a second injection creating a richer embedded mixture cloud, and a third stratified injection close to ignition time creating a locally enriched ignitable mixture at the spark plug region. This segmentation allows the engine to operate with overall lean mixture (reducing fuel consumption) while ensuring localized rich mixture for reliable ignition and controlled combustion (reducing particle emissions).
Solution Approach 2:
Different regions of the combustion chamber are given different fuel/air ratios: the overall cylinder volume maintains a lean mixture (λ>1) for fuel efficiency, while the spark plug region receives a locally enriched ignitable mixture for reliable combustion. This local quality differentiation resolves the contradiction between fuel efficiency and emission control.
2Use of energy by moving object
If the engine is operated with high excess of air in stratified mode to reduce fuel consumption, then fuel efficiency is improved, but exhaust-gas temperatures become very low causing catalytic converter to fall below light-off temperature
Solution Approach 1:
The first and second injections are performed in advance to create a lean background mixture and an embedded richer mixture cloud, preparing the combustion chamber for the final stratified injection. This preliminary action ensures that when the third injection occurs close to ignition time, the combustible mixture is already in position, allowing for reliable combustion and sufficient exhaust-gas temperature generation to maintain catalytic converter operation above light-off temperature while still operating with high excess air overall.
3Use of energy by moving object
If the engine is operated in homogeneous mode with high inert gas content to reduce throttling losses and fuel consumption, then fuel efficiency is improved, but running smoothness decreases drastically
Solution Approach 1:
The combustion chamber is differentiated into regions with different mixture qualities: a lean background mixture for overall fuel efficiency and an embedded richer mixture cloud with locally enriched ignitable mixture at the spark plug region. This local quality variation ensures reliable combustion and smooth engine operation even with high inert gas content and high excess air, while maintaining fuel efficiency benefits.
4Reliability
If the engine is operated in homogeneous mode at cold start to ensure reliable combustion, then combustion reliability is improved, but fuel accumulation on cold combustion chamber walls increases leading to high unburned hydrocarbon emissions
Solution Approach 1:
The first injection creates a lean background mixture that fills the combustion chamber, while the second injection creates a richer embedded mixture cloud and the third injection creates a locally enriched ignitable mixture at the spark plug region. This local quality differentiation ensures that fuel is concentrated where it can be reliably burned (spark plug region) while minimizing fuel contact with cold walls, thereby reducing unburned hydrocarbon emissions while maintaining combustion reliability.
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 reduces fuel consumption, minimizes pollutant emissions, and allows for flexible operating modes, enabling efficient engine operation with high inert gas content and rapid catalytic converter heating, even at low temperatures.
Implementation Method 1
by means of an injector, fuel is injected into the cylinder with the piston between top dead center and bottom dead center
Implementation Method 2
a fuel/air mixture is generated which is ignited at a predefinable ignition time by means of a spark plug in order to initiate a combustion
Implementation Method 3
a first stroke of a four-stroke cycle is an intake stroke followed by a compression stroke
Implementation Method 4
a fuel/air mixture is generated which is ignited at a predefinable ignition time by means of a spark plug in order to initiate a combustion
Data Source
AI summary
In a method for operating a spark-ignition, direct-injection internal combustion engine, wherein fuel is injected into a cylinder of the internal combustion engine and is ignited by a spark plug as a function of at least the load of the internal combustion engine, a crank angle is determined at which a first amount of fuel is injected into the cylinder during the intake stroke whereby a lean mixture is formed in the cylinder, subsequently, as a function of at least the load of the internal combustion engine, a crank angle is determined at which a second amount of fuel is injected, whereby a mixture cloud, which is richer than the lean mixture is formed in the lean mixture and a third amount of fuel is injected in the form of a stratified injection for forming a locally enriched and ignitable fuel/air mixture in the region of the spark plug close to an ignition time which is then ignited by the spark plug causing also combustion of the mixture cloud and the lean mixture.