Pre-chamber Ignition System for Lean Gas Engines
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Solution Overview
Problem
Spark ignited gaseous fuel internal combustion engines face challenges with incomplete combustion and poor ignitability due to lean air-fuel mixtures, leading to high nitrogen oxide generation, especially in large-bore engines.
Innovation Solution
A method and ignition system where pressurized fuel is supplied to an ignition region within the main combustion chamber or pre-chamber, creating a rich mixture by mixing with the existing lean air-fuel mixture shortly before ignition, using a spark igniter to initiate combustion and reduce nitrogen oxide generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a lean air-fuel mixture is used to reduce nitrogen oxide formation, then nitrogen oxide generation is reduced, but combustion completeness and ignitability deteriorate
Solution Approach 1:
The patent introduces a pre-chamber that creates a localized region with different mixture quality (enriched) compared to the main combustion chamber (lean). This local quality differentiation allows the pre-chamber to provide reliable ignition while the main chamber maintains lean combustion for reduced NOx emissions. The pre-chamber acts as a separate zone with optimized fuel-air ratio for ignition reliability.
Solution Approach 2:
The combustion chamber is segmented into two distinct parts: a pre-chamber and a main combustion chamber. This segmentation allows independent optimization of each zone - the pre-chamber for ignition reliability with enriched mixture, and the main chamber for low emissions with lean mixture. The flow passages connect these segments while maintaining their functional independence.
2Object-generated harmful factors
If a lean air-fuel mixture is used to reduce nitrogen oxide formation, then nitrogen oxide generation is reduced, but ignitability deteriorates
Solution Approach 1:
The pre-chamber creates a localized enriched mixture zone that provides excellent ignitability characteristics. This local quality enhancement at the ignition source (pre-chamber) does not compromise the overall lean mixture in the main combustion chamber, thus maintaining low NOx emissions while improving ease of ignition.
Solution Approach 2:
The pre-chamber performs preliminary combustion of a portion of the fuel before the main combustion event. This preliminary action creates hot gases and a flame front that propagate into the main combustion chamber, facilitating easier and more reliable ignition of the lean mixture in the main chamber.
3Reliability
If a pre-chamber is added to improve ignitability, then ignition reliability improves, but device complexity increases
Solution Approach 1:
The pre-chamber and main combustion chamber are merged into a single integrated combustion system with controlled fluid communication through flow passages. This merging allows the pre-chamber to function as an ignition enhancement device while the overall system operates as a unified combustion chamber, reducing the need for separate ignition systems and associated complexity.
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 ensures reliable ignition and significantly reduces nitrogen oxide production by creating a stratified air-fuel mixture with a mixing gradient, enhancing combustion efficiency and reducing NOx generation.
Implementation Method 1
creating a rich mixture by mixing with the existing lean air-fuel mixture shortly before ignition
Implementation Method 2
using a spark igniter to initiate combustion
Implementation Method 3
Ignition of the enriched mixture causes a flame front of hot gases that propagates from the pre-chamber via the flow transfer passages into the main combustion chamber
Data Source
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AI summary
The present disclosure generally relates to a method for operating a gaseous fuel internal combustion engine including at least one main combustion chamber (8) and at least one ignition device (34) configured to initiate an ignition event within the ignition region (38). The disclosed method may comprise supplying pressurized fuel to the ignition region (38) at times between about 30° to about 0°, particularly between about 10° to about 2° crank angle before the ignition event is initiated by the ignition device (34) for enriching the ignition region (38) with fuel, and initiating an ignition event in the ignition region (38) for combusting the enriched air/fuel mixture within the ignition region (38).