Pre-chamber Spark Plug Flame Kernel Flow Control
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Solution Overview
Problem
Conventional spark plugs face challenges in achieving repeatable and controllable ignition delay time and are sensitive to manufacturing variations and high combustion temperatures, leading to poor fuel efficiency and short operational life in lean fuel mixture engines.
Innovation Solution
A pre-chamber spark plug design featuring a tubular ground electrode and center electrode with a specific geometry that controls flame kernel development and ignition delay, using a method that includes precise gap creation and laser ignition to enhance combustion efficiency and longevity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional spark plugs are used to ignite lean fuel mixtures, then the engine can operate with excess air, but combustion quality deteriorates with misfires, incomplete combustion and poor fuel economy
Solution Approach 1:
The combustion chamber is divided into two parts: a pre-chamber where ignition occurs and a main chamber where the bulk combustion takes place. The pre-chamber contains a spark plug and a small volume of fuel-air mixture that ignites first, then propagates flame into the main chamber through discharge holes, improving combustion reliability and efficiency
Solution Approach 2:
The pre-chamber performs preliminary combustion of a small portion of the fuel-air mixture before the main chamber combustion. This preliminary action creates a more reliable ignition source and improves overall combustion quality, enabling better fuel economy without misfires or incomplete combustion
2Reliability
If high energy spark is used to improve combustion of lean fuel mixtures, then ignition reliability improves, but spark plug life decreases due to short spark plug life
Solution Approach 1:
Instead of using extremely high energy spark continuously, the system uses a moderate energy spark in the pre-chamber that is sufficient to ignite the smaller volume of mixture there. This partial action approach achieves reliable ignition while reducing electrode erosion and extending spark plug life
3Reliability
If pre-chamber spark plugs are used to enhance lean flammability limits, then combustion performance improves, but manufacturing variation sensitivity increases leading to higher coefficient of variation and misfire
Solution Approach 1:
The invention optimizes specific parameters of the pre-chamber design including the volume ratio of pre-chamber to main chamber, the size and number of discharge holes, and the spark gap dimensions. These parameter changes create a design that is more tolerant of manufacturing variations while maintaining improved combustion performance and lower coefficient of variation
4Manufacturing precision
If conventional spark plug design is used, then manufacturing is simpler, but repeatable and controllable ignition delay time cannot be achieved
Solution Approach 1:
The spark plug design segments the combustion process into pre-chamber ignition and main chamber combustion. This segmentation enables controllable ignition delay time by adjusting pre-chamber volume, discharge hole characteristics, and fuel-air mixture distribution, achieving repeatable ignition timing despite increased design 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
The design achieves repeatable and efficient combustion with low coefficient of variation, improved fuel efficiency, and extended spark plug life by optimizing flame jet velocity and penetration, reducing sensitivity to manufacturing variations and high temperatures.
Implementation Method 1
igniting the air/fuel mixture in the pre-chamber with an electric spark
Implementation Method 2
The flame kernel is transported to a back chamber of the pre-chamber... igniting the secondary flow of the air/fuel mixture creates a pressure rise in the pre-chamber
Data Source
AI summary
A pre-chamber spark plug that includes a shell. Additionally, the pre-chamber spark plug includes an insulator disposed within the shell. In a particular embodiment, a center electrode has a first portion surrounded by the insulator, and a second portion that extends from the insulator into a pre-chamber. The pre-chamber defined by the shell. In a further embodiment, a ground electrode is attached to the insulator. In particular embodiments, the ground electrode is tubular in shape and includes an inner spark surface ring spaced in surrounding relation to the center electrode to create a spark gap, an outer ring attached to the shell, and a plurality of rounded spokes connecting the inner and outer rings. In a particular embodiment, the ground and center electrodes accommodate attachment of precious metal alloys to increase electrode surface life. In another embodiment the ground electrode and insulator is coaxial to the center electrode.