Passive Prechamber Direct Injection Combustion Engine Knock Control
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Solution Overview
Problem
Internal combustion engines face challenges in achieving high compression ratios while preventing engine knock and maintaining low emissions, particularly when using natural gas as fuel, as existing systems either require complex dual fuel systems or compromise on efficiency and combustion phasing.
Innovation Solution
A direct injection system with a parallel passive prechamber and integrated igniter, where fuel is injected into the main combustion chamber and mixed air is ingested into the prechamber, allowing for controlled air-fuel ratios and delayed ignition to prevent auto-ignition reactions, thus avoiding knock and optimizing combustion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high compression ratio is used to improve combustion efficiency, then combustion efficiency is improved, but engine knock occurs
Solution Approach 1:
The combustion chamber is divided into a prechamber and a main chamber. Fuel is injected into the prechamber where it mixes with air and burns first, then the combustion propagates to the main chamber. This segmentation allows high compression ratio operation while controlling knock through staged combustion.
Solution Approach 2:
Fuel is injected and mixed with air in the prechamber before the main combustion event. The prechamber combustion occurs first, creating a controlled ignition source that propagates to the main chamber, preventing uncontrolled auto-ignition and knock.
2Reliability
If diesel fuel is used as pilot fuel to ignite natural gas, then ignition reliability is improved, but system complexity increases
Solution Approach 1:
The single fuel injection system serves multiple functions: it injects fuel into the prechamber for mixing and ignition, and also supplies fuel to the main chamber. This eliminates the need for separate pilot fuel injection systems while maintaining reliable ignition.
Solution Approach 2:
The system uses a portion of the main fuel injection to create the prechamber mixture that will ignite the main combustion. The fuel system serves itself by using injected fuel to create its own ignition source, eliminating external pilot fuel requirements.
3Productivity
If fuel is injected early to improve combustion phasing, then combustion phasing is improved, but auto-ignition reactions occur causing knock
Solution Approach 1:
The combustion process is segmented into prechamber combustion and main chamber combustion. Early fuel injection into the prechamber allows controlled mixing and staged burning, separating the ignition event from the main combustion to prevent knock.
Solution Approach 2:
The prechamber acts as an intermediary chamber between fuel injection and main chamber combustion. Fuel injected early mixes with air in the prechamber and burns there first, mediating the combustion process to prevent direct auto-ignition in the main chamber.
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 enables high compression ratios with reduced knock risk, efficient combustion phasing, and lower emissions by controlling the air-fuel ratio and injection timing, allowing for fast and efficient combustion without the need for complex dual fuel systems.
Implementation Method 1
mixed air is ingested into the prechamber during compression
Implementation Method 2
ignited. Hot gas generated by igniting a mixture of gaseous fuel and air in the prechamber
Implementation Method 3
fuel is directly injected into the combustion chamber to mix with air in the combustion chamber
Data Source
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AI summary
An injector-igniter assembly includes a passive prechamber and a fuel injector. In an internal combustion engine, fuel is directly injected into a combustion chamber to mix with air in the combustion chamber. Embodiments enable filing the prechamber at different air-fuel-ratio than the main chamber without directly filling the prechamber with fuel. The prechamber has jet apertures in fluid communication with the combustion chamber. In operation, fuel is injected directly into the combustion chamber though nozzles to form a cloud adjacent to openings into the prechamber. Subsequently, mixed fuel and air is ingested into the prechamber from the combustion chamber and ignited. The degree of mixing prior to ingestion into the prechamber can be controlled using different nozzles configurations. Ignited gaseous fuel and air is expelled from the prechamber through the jet apertures and into the combustion chamber as a flaming jet with a core of gaseous fuel.