Flex-Fuel Engine Injection Splitting for Soot Reduction
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Solution Overview
Problem
Flex-fuel vehicles with direct injection engines face challenges in reducing particulate matter emissions due to late fuel injection timing and varying fuel compositions, which can lead to increased soot generation and degraded combustion stability, especially during cold starts and when using alcohol fuels.
Innovation Solution
A method that adjusts fuel injection profiles based on alcohol content, splitting fuel injections between port and direct injection to expedite catalyst activation while minimizing soot emissions, involving initial port injection during closed intake valve events and multiple direct injections during compression and intake strokes, and transitioning to different injection profiles based on engine conditions and speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If direct injection is used to take advantage of increased charge cooling effects and increased octane, then knock limitations are addressed, but particulate matter emissions increase due to diffuse flame propagation and insufficient fuel-air mixing
Solution Approach 1:
The fuel injection process is segmented into multiple stages: initial port fuel injection to establish proper air-fuel mixture, followed by multiple direct injection pulses. This segmentation allows the benefits of both port injection (good mixing) and direct injection (charge cooling, knock resistance) to be combined, reducing soot formation while maintaining charge cooling effects.
Solution Approach 2:
Port fuel injection is performed as a preliminary action before direct injection to pre-mix fuel with air in the intake port. This preliminary mixing ensures that when direct injection occurs, the fuel is already partially prepared for combustion, reducing diffuse flame propagation and soot generation while still allowing direct injection to provide charge cooling.
2Temperature
If direct injection is performed late to take advantage of charge cooling, then knock limitations are reduced, but there is insufficient time for fuel mixing with air, generating soot
Solution Approach 1:
The injection process is divided into port injection phase (for mixing) and direct injection phases (for charge cooling and combustion). This temporal segmentation allows sufficient mixing time during port injection while still achieving the charge cooling benefits of late direct injection, resolving the contradiction between mixing quality and cooling effectiveness.
Solution Approach 2:
Fuel is injected into the intake port before the compression stroke to allow adequate mixing time with incoming air. This preliminary action ensures proper air-fuel mixture formation before direct injection occurs, preventing soot generation while maintaining the timing benefits for charge cooling.
3Object-generated harmful factors
If fuel injection amount from direct injector is decreased and port injector is increased to reduce soot load, then particulate matter emissions are reduced, but catalyst activation is delayed
Solution Approach 1:
The fuel injection is segmented into multiple direct injection pulses distributed across several combustion events. This segmentation maintains total fuel delivery for catalyst heating while distributing the thermal load to prevent excessive soot formation, achieving both emission reduction and timely catalyst activation.
Solution Approach 2:
Multiple direct injection pulses are applied across multiple combustion events to maintain continuous thermal input for catalyst activation. This continuous action ensures the catalyst reaches operating temperature without requiring excessive single-event injection that would generate soot, balancing catalyst activation timing with emission control.
4Temperature
If alcohol fuel is used to increase charge cooling and octane, then knock limitations are addressed, but combustion stability degrades and misfire increases during cold start
Solution Approach 1:
Fuel injection is segmented into port injection (for stable mixture formation) and direct injection (for charge cooling). This segmentation allows the engine to achieve reliable combustion during cold start through port injection while still benefiting from alcohol fuel's charge cooling effects through controlled direct injection, improving rather than degrading combustion stability.
Solution Approach 2:
The injection strategy dynamically adjusts the port-to-direct injection split ratio based on operating conditions including cold start status. During cold start, the system optimizes the balance between port and direct injection to ensure combustion stability while still achieving charge cooling benefits, preventing misfire.
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 particulate matter emissions, improves engine performance, and enhances fuel economy by optimizing fuel injection timing and split ratios, ensuring lower emissions and stable combustion across varying fuel compositions and engine conditions.
Implementation Method 1
direct injection of an ethanol fuel may be used to take advantage of the increased charge cooling effects of the alcohol fuel's higher heat of vaporization
Implementation Method 2
port fuel injectors that inject fuel into a cylinder port (port fuel injection)
Implementation Method 3
direct fuel injectors that inject fuel directly into a combustion cylinder (direct injection)
Implementation Method 4
combustion cylinder
Data Source
AI summary
Methods and systems are provided for controlling exhaust emissions by adjusting an injection profile for fuel injected into an engine cylinder from a plurality of fuel injectors during engine start and crank. By splitting injection of fuel during start so that a portion of fuel is port injected and a remaining portion is direct injected as one or multiple injections, the soot load of the engine can be reduced and fuel economy can be improved. The injections are adjusted based on the alcohol content of the injected fuel to take advantage of the charge cooling properties of the fuel.