Corona Igniter Shell Gap Width Control
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Solution Overview
Problem
Existing corona igniter systems experience significant energy loss and unwanted arc discharge due to voltage drops and ionized air migration between the central electrode and the metal shell, reducing the effectiveness of corona discharge and ignition quality.
Innovation Solution
The design incorporates a shell with an increasing gap width between the shell and the insulator, which controls the location of the corona discharge and enhances its concentration, reducing the likelihood of arc discharge by increasing the distance for conductive path formation and encouraging corona discharge to migrate out of the shell gap.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a uniform gap width is maintained between the shell and insulator, then the manufacturing precision is improved, but the corona discharge location control deteriorates and energy loss increases
Solution Approach 1:
The shell gap width is designed to vary along the longitudinal axis of the igniter, with a wider gap at the firing end and a narrower gap at the base. This non-uniform gap distribution creates localized electric field enhancement at the firing end where corona discharge is desired, while reducing electric field strength at the base where arc discharge should be prevented. The local variation in gap width allows optimization of discharge characteristics at different positions without requiring uniform manufacturing precision throughout the entire structure.
2Reliability
If the gap width between shell and insulator is increased, then arc discharge is reduced, but the corona discharge effectiveness deteriorates
Solution Approach 1:
The shell gap width varies longitudinally to provide different gap widths at different positions: a wider gap at the base for arc discharge prevention and a narrower gap at the firing end for corona discharge enhancement. This localized variation in gap width allows each region to be optimized for its specific function.
Solution Approach 2:
The solution transitions from a uniform one-dimensional gap width to a two-dimensional variable gap width that changes along the longitudinal axis. This dimensional variation allows the system to simultaneously achieve contradictory goals at different positions along the igniter length.
3Productivity
If a narrower shell gap is used, then corona discharge is enhanced, but arc discharge between central electrode and shell increases
Solution Approach 1:
The shell gap width is optimized locally at different positions: a narrow gap at the firing end to enhance corona discharge intensity and a wide gap at the base to prevent arc discharge. This spatial variation in gap width resolves the contradiction between corona discharge enhancement and arc discharge prevention.
4Device complexity
If the shell gap width is uniform, then the device complexity is reduced, but the ignition quality deteriorates due to uncontrolled corona discharge location
Solution Approach 1:
The shell is designed with a longitudinally varying gap width that creates localized electric field enhancement at the firing end, controlling corona discharge location and improving ignition quality. While this increases structural complexity compared to a uniform gap design, the variation is achieved through simple geometric modifications to the shell geometry rather than complex additional 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 design provides a more controlled and robust corona discharge, improving ignition quality and reducing energy loss by maintaining dielectric properties and preventing unwanted arc formation between the central electrode and the shell.
Implementation Method 1
a central electrode formed of an electrically conductive material for receiving a high radio frequency voltage and emitting a radio frequency electric field to ionize a fuel-air mixture and provide the corona discharge
Implementation Method 2
The electric field causes a portion of a mixture of fuel and air in the combustion chamber to ionize and begin dielectric breakdown, facilitating combustion of the fuel-air mixture
Implementation Method 3
An insulator formed of an electrically insulating material surrounds the central electrode and is received in a metal shell
Implementation Method 4
The shell gap width increases toward the shell lower end... controls the location of the corona discharge and enhances the corona discharge between the central electrode and the shell
Implementation Method 5
The electric field is controlled so that the fuel-air mixture maintains dielectric properties and corona discharge occurs at the electrode firing end
Data Source
AI summary
A corona igniter 20 includes an insulator 28 surrounding a central electrode 24 and a shell 30 surrounding the insulator 28. The shell 30 presents a shell gap 38 having a shell gap width ws between a shell lower end 34 and a shell inner surface 90 or shell outer surface 92. The shell 30 has a shell thickness ts decreasing toward the shell lower end 34 allowing the shell gap width ws to increase toward the shell lower end 34. The shell gap 38 is open at the shell lower end 34 allowing air to flow therein, and the shell gap width ws is greatest at the shell lower end 34. The increasing shell gap width ws enhances corona discharge 22 along the insulator 28 between the central electrode 24 and shell 30.