Ignition Plug Insulator Geometry for Pre-Ignition Control
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Solution Overview
Problem
The existing ignition devices for internal combustion engines face issues with pre-ignition due to excessive heating of the insulator, which reduces ignitability and leads to engine damage, and carbon accumulation decreases the amount of generated non-equilibrium plasma.
Innovation Solution
The ignition plug design includes a center electrode and insulator configuration where the insulator projects into the combustion chamber with specific volume ratios and diameter differences to ensure sufficient heat conduction and prevent pre-ignition, while maintaining a temperature that prevents carbon accumulation, thereby improving ignitability and vibration resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the insulator projects longer into the combustion chamber to increase non-equilibrium plasma generation, then ignitability is improved, but the insulator temperature excessively increases causing pre-ignition
Solution Approach 1:
The insulator is designed with different diameters at different portions: a larger diameter at the front side (projection portion) and a smaller diameter at the rear side (base portion). This local variation in geometry allows the front portion to generate sufficient non-equilibrium plasma for improved ignitability, while the reduced rear portion minimizes heat accumulation and prevents pre-ignition.
2Quantity of substance
If the insulator projects longer into the combustion chamber to increase non-equilibrium plasma generation, then the amount of non-equilibrium plasma is increased, but pre-ignition occurs causing engine damage
Solution Approach 1:
The insulator features a front-side projection portion with larger diameter for generating non-equilibrium plasma, and a rear-side base portion with smaller diameter to reduce heat accumulation. This local differentiation enables sufficient plasma generation while preventing excessive insulator heating that would cause pre-ignition and engine damage.
3Loss of energy
If the insulator diameter is increased to improve heat conduction, then heat conduction is enhanced, but the volume of non-equilibrium plasma generation is reduced
Solution Approach 1:
The insulator is designed with a larger diameter at the front projection portion to provide sufficient volume for non-equilibrium plasma generation, and a smaller diameter at the rear base portion to improve heat conduction efficiency. This local differentiation resolves the contradiction by optimizing each portion for its specific function.
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 effectively prevents pre-ignition and carbon accumulation, enhancing ignitability and the amount of non-equilibrium plasma generated, while maintaining sufficient heat conduction and vibration resistance.
Implementation Method 1
the insulator projects into the combustion chamber with specific volume ratios and diameter differences to ensure sufficient heat conduction
Implementation Method 2
generates non-equilibrium plasma on the surface of the insulator by applying an AC voltage to the center electrode or applying a pulse voltage a plurality of times to the center electrode
Data Source
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AI summary
In an ignition plug (10), the volume V1 of a portion of an insulator (200), which projects from a metallic shell (300) to a front side (-Z), is equal to or greater than 45 mm3; and an expression 0.18 ≤ V2/V1 ≤ 0.37 is satisfied, where H is a length along which the insulator (200) projects from the metallic shell (300) to the front side in an axial direction (Z), and V2 is a volume of a portion of the insulator (200), which projects from a front end of the insulator (200) along a length H/2 in the axial direction (Z).