Split Fuel Injection for Engine Emission Control
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Solution Overview
Problem
Multi-fuel engine systems face challenges in reducing particulate matter (PM) emissions due to late direct injection and varying fuel properties, which can lead to increased soot generation and degradation of fuel economy and combustion stability, especially during cold starts.
Innovation Solution
A method involving a split fuel injection profile where a first fuel with lower alcohol content or volatility is port injected during a closed intake valve event, and a second fuel with higher alcohol content or volatility is direct injected over multiple injections, optimizing the injection timing and ratio based on fuel properties to expedite catalyst light-off and reduce PM emissions without degrading combustion stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If direct injection is used to improve power output and reduce emissions, then fuel efficiency and power are improved, but particulate matter emissions increase due to insufficient mixing time and turbulence
Solution Approach 1:
The fuel injection process is segmented into multiple injection events (first injection and second injection) within a single combustion cycle. The first injection occurs during the intake stroke to allow mixing, and the second injection occurs during the compression stroke to enhance combustion. This segmentation resolves the contradiction by providing both mixing time and combustion efficiency.
Solution Approach 2:
The first fuel injection is performed preliminarily during the intake stroke before compression, allowing the fuel to mix with air in advance. This preliminary action ensures adequate mixing time and turbulence exposure, preventing soot formation while maintaining the capability for efficient combustion during the compression stroke injection.
2Power
If direct injection timing is delayed to improve combustion efficiency, then power output increases, but mixing time decreases leading to increased soot generation
Solution Approach 1:
The injection timing is segmented into two distinct phases: an early injection during the intake stroke for mixing, and a later injection during the compression stroke for efficient combustion. This segmentation allows the system to benefit from both early mixing (reducing soot) and late injection (improving combustion efficiency).
Solution Approach 2:
The fuel injection process maintains continuity of useful action by ensuring that fuel is continuously present in the cylinder through two injection events. The first injection establishes the fuel-air mixture during intake, and the second injection maintains combustion efficiency during compression, ensuring uninterrupted beneficial effects throughout the cycle.
3Object-generated harmful factors
If port injection is increased to reduce soot emissions, then PM emissions decrease, but fuel economy and power output are degraded
Solution Approach 1:
The fuel delivery system is segmented between port injection and direct injection, with each serving a different function. Port injection provides initial fuel delivery with good mixing characteristics (reducing soot), while direct injection during compression stroke provides precise combustion control (maintaining efficiency). This segmentation allows both benefits to coexist.
Solution Approach 2:
Different injection locations are assigned different qualities/functions: port injection is optimized for mixing and soot reduction, while direct injection into the combustion chamber is optimized for combustion efficiency and fuel economy. This local quality differentiation resolves the contradiction by allowing each injection method to excel at its intended function.
4Reliability
If higher alcohol content fuel is used to improve octane and reduce knock, then knock resistance increases, but cold-start combustion stability and fuel economy are degraded
Solution Approach 1:
The fuel injection strategy is segmented to accommodate different fuel properties: port injection of higher alcohol content fuel provides knock resistance during the intake stroke, while the timing and amount of direct injection during compression stroke are adjusted to ensure stable combustion despite the fuel's lower volatility during cold conditions.
Solution Approach 2:
Injection parameters (timing, duration, amount) are dynamically changed based on fuel alcohol content and engine temperature. During cold starts, the control system adjusts the injection strategy to ensure adequate mixing and combustion stability, while maintaining the knock-resistant properties of high-alcohol fuel through appropriate injection timing and quantity control.
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 reduces PM emissions and improves engine performance and fuel economy by leveraging the properties of different fuels, allowing for faster catalyst activation and increased tolerance to spark retard without compromising combustion stability.
Implementation Method 1
port injecting a first amount of a first fuel during a closed intake valve event
Implementation Method 2
direct injecting a second amount of a second fuel over multiple injections of the first combustion event
Implementation Method 3
the direct injection of the alcohol fuel may take advantage of the increased charge cooling effects of the alcohol fuel's higher heat of vaporization
Implementation Method 4
direct injecting a second amount of a second fuel over multiple injections of the first combustion event
Data Source
AI summary
Methods and systems are provided for controlling exhaust emissions by adjusting an injection profile for different fuels injected into an engine cylinder from different fuel injectors during engine start and crank. By splitting fuel injection during start and cranking so that fuel of lower alcohol content is port injected and fuel of higher alcohol content is direct injected as one or multiple injections, the soot load of the engine can be reduced and fuel economy can be improved.