Pre-Chamber Ignition Jets for Lean Combustion NOx Reduction
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Solution Overview
Problem
Internal combustion engines face challenges in reducing NOx emissions while maintaining complete combustion, as lean charge air-gaseous fuel mixtures can lead to incomplete combustion and high NOx production in both the pre-combustion and main combustion chambers.
Innovation Solution
The engine employs ignition jets with azimuthally inclined directions relative to the radial directions, combined with a counter-flow system within the main combustion chamber, enhancing the relative velocity and turbulence between the ignition jets and the lean charge air-gaseous fuel mixture to improve ignition efficiency and reduce NOx emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a lean charge air-gaseous fuel mixture is used in the main combustion chamber, then NOx emissions are reduced, but incomplete combustion and poor ignitability occur
Solution Approach 1:
The combustion chamber is divided into two segments: a pre-combustion chamber for initial ignition and a main combustion chamber for complete combustion. This segmentation allows the lean mixture to be ignited reliably in the pre-chamber while completing combustion in the main chamber, resolving the contradiction between lean operation and combustion completeness.
Solution Approach 2:
The pre-combustion chamber acts as an intermediary that generates ignition jets to ignite the lean charge air-gaseous fuel mixture in the main combustion chamber. This intermediary mechanism enables reliable ignition of lean mixtures that would otherwise be difficult to ignite directly.
2Reliability
If a pre-combustion chamber with stoichiometric or under stoichiometric combustion is used, then ignition reliability is improved, but NOx emissions increase
Solution Approach 1:
Different combustion conditions are applied in different locations: the pre-combustion chamber uses stoichiometric or under stoichiometric combustion for reliable ignition, while the main combustion chamber uses lean combustion for low NOx emissions. This local differentiation resolves the contradiction between ignition reliability and emission reduction.
Solution Approach 2:
The combustion process is segmented into two stages with different air-to-fuel ratios: rich combustion in the pre-chamber for ignition reliability and lean combustion in the main chamber for emission control. This segmentation allows each zone to optimize for its specific function.
3Productivity
If the peak combustion temperature in the main combustion chamber is increased, then combustion efficiency is improved, but NOx emissions increase
Solution Approach 1:
The pre-combustion chamber performs preliminary combustion to generate hot ignition jets before the main combustion event. This preliminary action provides sufficient ignition energy for the lean mixture in the main chamber, allowing complete combustion at lower peak temperatures and thus reducing NOx emissions while maintaining 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 effectively decreases energy combustion in the pre-combustion chamber, maintaining ignition performance while lowering NOx emissions by ensuring sufficient ignition and complete combustion in the main chamber.
Implementation Method 1
Ignition of the fuel within the pre-combustion chamber creates a flame front of burning fuel that is jetted through the flow transfer passages into the main combustion chamber
Implementation Method 2
enhancing the relative velocity and turbulence between the ignition jets and the lean charge air-gaseous fuel mixture to improve ignition efficiency
Implementation Method 3
Ignition of the fuel within the pre-combustion chamber creates a flame front of burning fuel
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
An internal combustion engine (1) for operation on at least partly gaseous fuel under adjusted flow dynamics comprises an engine block cylinder unit section (3) providing a main combustion chamber (5), and a cylinder head (11) covering the main combustion chamber (5). The cylinder head (11) comprises an intake channel (13) for providing a charge air-gaseous fuel mixture through an intake opening (13A) into the main combustion chamber (5) and an ignition source (31) for igniting the charge air-gaseous fuel mixture within the main combustion chamber (5). The ignition source (31) is configured for providing ignition jets (35) into the main combustion chamber (5) along injection directions (VJ). The internal combustion engine (1) is further configured to generate a flow system (F) of the charge air-gaseous fuel mixture within the main combustion chamber (5) such that the flow system (F) includes at least one counter flow section (C) that at least partly spatially overlaps with a respective one of the ignition jets (35) and has a flow direction (VF) directed at least partly against the respective injection direction (VJ). Thereby, the amount of the ignited charge air-gaseous fuel mixture may be increased.