Oil Droplet Injection for Lean Burn Engine Combustion
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Solution Overview
Problem
Natural gas reciprocating engines face challenges in reducing NOx emissions and achieving efficient combustion, as existing methods rely heavily on spark plug ignition, which may not be effective at high loads and lean fuel-air mixtures.
Innovation Solution
The system introduces oil droplets into the combustion chamber through dedicated channels in the cylinder head and valve seat inserts, providing multiple ignition sources that can self-ignite without spark plug assistance, allowing for varied ignition timing through early spark events to alter in-cylinder charge temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If spark plug ignition is used to ignite lean homogeneous mixture, then combustion can be initiated, but combustion efficiency deteriorates at high loads and lean fuel-air mixtures
Solution Approach 1:
The ignition system is segmented into multiple distributed oil droplet ignition sources throughout the combustion chamber, rather than relying on a single spark plug. This segmentation provides multiple ignition points that can simultaneously ignite the lean homogeneous mixture, improving both ignition reliability and combustion efficiency at high loads
Solution Approach 2:
Oil droplets are introduced as an intermediary substance to facilitate ignition. The oil droplets are easier to ignite than the lean natural gas mixture, and once ignited, they provide sustained combustion that ignites the surrounding lean mixture, thereby improving combustion efficiency while maintaining ignition reliability
2Object-generated harmful factors
If lean homogeneous mixture is used to reduce NOx emissions, then harmful emissions are reduced, but combustion stability deteriorates
Solution Approach 1:
Oil droplets serve as an intermediary that stabilizes combustion in lean homogeneous mixtures. The oil droplets ignite more readily and provide sustained heat release that stabilizes the combustion process, allowing the engine to operate with lean mixtures for NOx reduction without sacrificing combustion stability
Solution Approach 2:
The combustion characteristics are changed by introducing oil droplets with different physical properties (liquid phase, higher energy density) into the lean gas mixture. This parameter change enables stable combustion at lower equivalence ratios, maintaining combustion stability while achieving lean burn conditions for NOx reduction
3Productivity
If multiple distributed ignition sources are created using oil droplets, then combustion efficiency is improved, but device complexity increases
Solution Approach 1:
The oil system serves multiple functions: it provides lubrication for the engine and simultaneously serves as the distributed ignition source. This multi-functionality eliminates the need for a separate ignition injection system, reducing device complexity while achieving multiple distributed ignition sources for improved combustion efficiency
Solution Approach 2:
The existing oil circulation system in the engine is utilized to provide the distributed ignition sources. The oil that would otherwise only serve lubrication purposes is now also used for ignition, allowing the system to serve itself and eliminating the need for additional dedicated ignition components
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 sustained distributed ignition at high engine loads, reducing the reliance on spark plug ignition and improving combustion efficiency and emission reduction, particularly by achieving self-sustained ignition and altering the in-cylinder charge temperature for optimal combustion.
Implementation Method 1
introducing a pilot fuel such as lubricating oil into the air intake passage. The oil droplets are earned along by the air passing through the intake passage and into the cylinder
Implementation Method 2
ignition timing of distributed oil droplets can be changed using a very early spark event to combust a small amount of in-cylinder charge to alter the in-cylinder charge temperature
Implementation Method 3
A spark plug may be activated at the desired time to ignite the combustion charge which results in increasing the pressure and hence the temperature in the combustion chamber
Data Source
AI summary
A system and method is provided that introduces oil droplets into the combustion chamber of a lean burn natural gas engine via dedicated channels located in the cylinder head and a valve seat insert for providing multiple distributed sources of ignition in addition to the spark plug based ignition system.