Dual Fuel Injection for Lean-Burn Engine Backfire Prevention
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Solution Overview
Problem
Conventional fuel injection systems for internal combustion engines, particularly those using alternative fuels like hydrogen, are prone to misfires, backfires, and explosive events due to high flammability, requiring complex and expensive injectors, which are not readily available in all sizes.
Innovation Solution
The system controls the lambda value of the air-fuel mixture to be higher than 3 via intake valves and enriches it with fuel directly injected into the combustion chamber, using smaller and simpler injectors, and optionally incorporates exhaust gas recirculation to reduce flammability and combustibility risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fuel injection systems are used to supply air-fuel mixture to the intake manifold, then the fuel air mixture is created in or before the intake manifold with the total amount of fuel, but this creates large volumes of fuel air mixture with high tendency to combust, leading to misfires, backfires, or explosive events in the supply system
Solution Approach 1:
The fuel injection process is segmented into two distinct stages: first, a lean air-fuel mixture (lambda > 3) is supplied to the intake manifold to ensure safety; second, additional fuel is injected directly into the combustion chamber to achieve the required stoichiometric ratio. This segmentation separates the fuel supply function from the mixing function, allowing safe transport of fuel vapor while maintaining reliable combustion.
Solution Approach 2:
The intake manifold acts as an intermediary chamber where a lean, safe air-fuel mixture is temporarily held before entering the combustion chamber. This intermediary approach allows the system to transport fuel vapor safely through the intake system while still delivering the necessary fuel quantity to the combustion chamber through direct injection.
2Ease of manufacture
If injectors are used to directly generate the air-fuel mixture provided for the main combustion engine, then the fuel can be injected directly into the main combustion chamber, but starting at a certain size of the internal combustion engines the injectors have to be constructed and manufactured with complex structures and/or big dimensions, substantially increasing the effort and costs for the manufacturing process
Solution Approach 1:
The fuel delivery system is segmented into two independent injection systems: a port injection system that supplies lean mixture to the intake manifold, and a direct injection system that adds fuel directly to the combustion chamber. This allows the use of simpler, smaller injectors in the direct injection system while still achieving the required total fuel quantity for large engine displacements.
Solution Approach 2:
The dual injection system provides multi-functionality: the port injection system handles the bulk of fuel delivery in a safe, simplified manner, while the direct injection system fine-tunes the mixture and ensures proper combustion chamber filling. This universal approach works for engines of various sizes without requiring proportionally larger and more complex single injectors.
3Reliability
If the air-fuel mixture is supplied with lambda value higher than 3 via intake valves, then the risk of misfires and backfires is reduced, but additional fuel must be injected directly into the combustion chamber to achieve proper combustion
Solution Approach 1:
The injection system is segmented into two functional parts: port injection for safe, lean mixture delivery that prevents backfires, and direct injection for precise fuel metering in the combustion chamber. This segmentation allows each subsystem to be optimized independently, managing overall system complexity through functional decomposition.
Solution Approach 2:
The system dynamically changes the lambda parameter through two-stage fuel delivery: first maintaining lambda > 3 in the intake system for safety, then adjusting the overall mixture to proper stoichiometric ratios in the combustion chamber through direct injection. This parameter management approach resolves the contradiction between safety and combustion efficiency.
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 the risk of misfires and backfires, allows the use of smaller, less complex injectors, and maintains efficient combustion, while achieving favorable costs and interchangeability across engine sizes.
Implementation Method 1
a fuel supply line fluidically connected to at least one fuel supply system, the at least one fuel supply system being configured to supply fuel, preferably hydrogen, directly into a main combustion chamber and/or a pre-combustion chamber
Implementation Method 2
at least one piston-cylinder unit in which an air-fuel mixture, preferably an air-hydrogen mixture, is combustible
Data Source
AI summary
An engine controller, for an internal combustion engine, is configured to:control at least one actuator to provide an air-fuel mixture with a lambda value higher than 3 to a main combustion chamber via at least one intake valve, wherein the at least one actuator is arranged upstream of at least one intake port or which is arranged in the intake port;control at least one fuel supply system to provide fuel directly to the main combustion chamber and/or a pre-combustion chamber of a piston-cylinder unit such that at the time of ignition of the air-fuel mixture the lambda value of that air-fuel mixture in the main combustion chamber is lower than the lambda value of the air-fuel mixture provided to the main combustion chamber via the at least one intake valve.