Pre-combustion Chamber Ignition for Lean Gas Engines
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Internal combustion engines operating on lean gaseous fuel mixtures face challenges with incomplete combustion and poor ignitability, leading to increased nitrogen oxide emissions, particularly in large-bore engines.
Innovation Solution
The method involves enriching a pre-combustion chamber with gaseous fuel and igniting it with a predefined amount of liquid ignition fuel, such as Diesel fuel, to reduce the total ignition fuel needed and lower the air-to-fuel ratio, while supplying gaseous fuel into the pre-combustion chamber between 210° crankangle before top dead center and 180° crankangle after top dead center during the exhaust and intake strokes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a lean air fuel mixture is used to reduce nitrogen oxide emissions, then nitrogen oxide formation is reduced, but combustion completeness and ignitability deteriorate
Solution Approach 1:
The combustion chamber is divided into a main combustion chamber and a pre-combustion chamber. The pre-chamber receives a portion of the lean air-fuel mixture and enriches it locally, creating a separate ignition zone. This segmentation allows the main chamber to maintain lean operation for NOx reduction while the pre-chamber provides reliable ignition through local enrichment.
Solution Approach 2:
The pre-combustion chamber creates a local region with enriched air-fuel mixture (different quality) compared to the lean mixture in the main combustion chamber. This local enrichment occurs through the geometry of the pre-chamber and flow transfer passages, providing good ignitability in the pre-chamber while maintaining overall lean operation for NOx reduction.
2Object-generated harmful factors
If a lean air fuel mixture is used to reduce nitrogen oxide emissions, then nitrogen oxide formation is reduced, but combustion completeness deteriorates
Solution Approach 1:
The combustion system is segmented into a pre-combustion chamber for ignition and a main combustion chamber for complete combustion. The pre-chamber generates intense combustion that propagates through the flow transfer passages into the main chamber, ensuring complete combustion of the lean mixture even though the overall air-fuel ratio remains high for NOx reduction.
Solution Approach 2:
The pre-combustion chamber performs preliminary combustion action by first igniting a portion of the air-fuel mixture. This preliminary combustion creates high-temperature gases that then propagate into the main combustion chamber, initiating and completing the combustion of the remaining lean mixture. This two-stage approach ensures complete combustion while maintaining lean overall operation.
3Reliability
If gaseous fuel is supplied during exhaust and intake strokes to enrich the pre-combustion chamber, then ignition reliability is improved, but the complexity of fuel supply timing control increases
Solution Approach 1:
Gaseous fuel is supplied to the pre-combustion chamber during specific periodic intervals - the exhaust stroke and intake stroke - rather than continuously. This periodic supply timing, synchronized with the engine cycle, ensures the pre-chamber is enriched at the appropriate moments for reliable ignition while allowing the system to return to lean operation during the power and compression strokes, reducing overall NOx emissions.
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 nitrogen oxide emissions while maintaining or improving engine efficiency by creating a stratified air/fuel mixture that minimizes NOx generation and enhances ignition reliability.
Implementation Method 1
The enriched mixture is ignited in the pre-chamber by an igniter such as a spark plug. 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.
Implementation Method 2
an ignition fuel injector for supplying liquid ignition fuel into the pre-combustion chamber for initiating an ignition event within the pre-combustion chamber
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The present disclosure relates to a method for operating an internal combustion engine operating at least partly on gaseous fuel. The internal combustion engine has a main combustion chamber (8) and a pre-combustion chamber assembly (20) with a pre-combustion chamber (36), a gaseous fuel supply channel (46) for supplying gaseous fuel into the pre-combustion chamber (36), and an ignition fuel injector (34) for supplying ignition fuel into the pre-combustion chamber (36). The method may comprise supplying a predefined amount of gaseous fuel into the pre-combustion chamber (36) via the gaseous fuel supply channel (46) for enriching the pre-combustion chamber (36) with gaseous fuel at times between about 210° crankangle before the top dead center and about 180° crankangle after the top dead center, and supplying a predefined amount of liquid ignition fuel into the gaseous fuel enriched pre-combustion chamber (36) via the at least one liquid ignition fuel injector (34).