Split Fuel Injection Mitigates Super Knock in Forced Induction Engines
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Solution Overview
Problem
Internal combustion engines with forced induction are prone to super knock, a condition where the air-fuel mixture pre-ignites, leading to high cylinder pressures that can damage engine components, especially at low-speed high-load operating conditions.
Innovation Solution
Implementing a split injection mode for fuel injectors, where fuel is injected in multiple pulses during the intake and compression strokes, with the later pulses occurring after the primary injection, to reduce the temperature of the air-fuel mixture and prevent pre-ignition, while maintaining an air-fuel ratio near stoichiometric to minimize engine knock.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If forced induction is used to increase mass air intake, then engine power is improved, but pre-ignition and super knock conditions occur leading to high cylinder pressures
Solution Approach 1:
The fuel injection process is segmented into multiple separate pulses (primary, secondary, and tertiary injections) rather than a single injection. This segmentation allows fuel to be introduced at different stages of the compression stroke, with later pulses cooling the air-fuel mixture to prevent pre-ignition while maintaining power output from forced induction.
2Object-affected harmful factors
If fuel is injected late in the compression stroke to reduce air-fuel mixture temperature, then pre-ignition is reduced, but engine power may be adversely affected
Solution Approach 1:
Fuel injection is performed as periodic pulses at specific intervals during the compression stroke. The multi-pulse injection pattern (primary, secondary, tertiary) provides periodic cooling action that prevents pre-ignition while the timing and duration of each pulse are optimized to maintain engine power.
3Object-affected harmful factors
If split injection mode is used to prevent pre-ignition, then super knock conditions are interrupted, but fuel injection complexity increases
Solution Approach 1:
The fuel injection system operates in different modes (single pulse or split injection) depending on engine operating conditions. The system dynamically selects between single pulse injection for normal operation and split injection mode (with primary, secondary, tertiary pulses) when pre-ignition risk is detected, allowing flexible adaptation without permanent complexity increase.
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 prevents pre-ignition and super knock conditions, maintaining engine power, reducing noise and fuel consumption, and ensuring high catalytic conversion efficiency without adverse effects on engine performance.
Implementation Method 1
The injection of fuel late in the compression stroke may reduce the temperature of the air-fuel mixture that is present in the combustion chamber
Implementation Method 2
the engine control module selects a fuel schedule that operates a fuel injector in a split injection mode in which fuel is injected into the combustion chamber in multiple, discrete pulses
Data Source
AI summary
An internal combustion engine according to one or more embodiments of the present disclosure may include an engine cylinder having a cylinder head and cylinder sidewalls and a piston that reciprocates within the engine cylinder. The piston, the cylinder head, and the cylinder sidewalls may at least partially define a combustion chamber. The internal combustion engine may also include a fuel injector that is positioned to inject fuel directly into the combustion chamber. The internal combustion engine may further include an engine control module that is in electronic communication with the fuel injector. The engine control module may determine if the internal combustion engine is operating at conditions corresponding to a super knock condition may occur and commands the fuel injector to operate under a split injection mode in which fuel is injected into the combustion chamber in a plurality of injection pulses.