Dielectric Barrier Discharge Cleaning for Engine Optical Windows
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Solution Overview
Problem
The optical window in laser-ignited engines becomes contaminated with combustion products, reducing the laser's intensity and preventing stable ignition, as existing solutions like material selection and laser pulse cleaning are inadequate.
Innovation Solution
An apparatus with a first electrode covered in dielectric material inside the optical window and a second electrode exposed around it, using a power supply to generate dielectric barrier discharge with high-frequency or pulsed voltage, creating radicals and airflow to clean the surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the optical window material is selected to raise the temperature of the optical window, then the contamination resistance is improved, but the risk of thermal damage and engine component damage increases
Solution Approach 1:
The patent replaces thermal cleaning mechanisms with a dielectric barrier discharge plasma cleaning system. electrodes are positioned on both sides of the optical window, and high-voltage pulses generate plasma discharge that cleans the optical window surface through chemical reactions and ion bombardment rather than thermal effects, thus avoiding thermal damage while maintaining cleaning effectiveness
Solution Approach 2:
The patent changes the cleaning mechanism from thermal to electrical/plasma-based. By applying high-voltage pulses (several kV to tens of kV) at specific frequencies, the system generates dielectric barrier discharge that produces reactive species for cleaning without the thermal side effects of heated materials
2Reliability
If the surface of the optical window is cleaned by irradiation with a laser pulse, then the cleaning effectiveness is improved, but the complexity of the system increases
Solution Approach 1:
The patent makes the laser system multi-functional by using it both for ignition and for generating plasma cleaning. The same laser pulses that ignite the air-fuel mixture also create plasma discharge on the optical window surface when combined with the electrode configuration, eliminating the need for separate cleaning laser systems
Solution Approach 2:
The patent merges the ignition function and cleaning function into a single integrated system. The laser pulses serve dual purposes: igniting combustion and generating plasma for optical window cleaning, while the electrodes and control unit coordinate both functions through unified control
3Reliability
If a high-frequency or pulsed voltage is applied to generate dielectric barrier discharge, then the cleaning ability is improved, but the energy consumption increases
Solution Approach 1:
The patent uses periodic pulsed voltage application synchronized with the engine cycle. The dielectric barrier discharge is generated only during specific phases (intake or exhaust strokes) when the piston position and chamber conditions are favorable, rather than continuous operation, reducing overall energy consumption while maintaining effective cleaning
Solution Approach 2:
The patent performs cleaning during the exhaust stroke before the next combustion cycle begins. This preliminary cleaning action removes contamination buildup before it significantly degrades optical performance, allowing for less frequent and lower-energy cleaning cycles
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 method effectively removes contamination from the optical window, ensuring stable laser ignition and engine operation by generating dielectric barrier discharge during the exhaust stroke, which removes soot and particulates, and discharges intermediate species affecting combustion.
Implementation Method 1
a power supply electrically coupled between the first electrode and the second electrode. The apparatus further includes a control unit that controls the power supply so as to generate dielectric barrier discharge along the surface of the optical window by applying a high-frequency or pulsed voltage between the first electrode and the second electrode
Implementation Method 2
a radical and an induced airflow are generated by the dielectric barrier discharge and remove contamination on the surface of the optical window
Implementation Method 3
a radical and an induced airflow are generated by the dielectric barrier discharge and remove contamination on the surface of the optical window
Data Source
AI summary
An apparatus for cleaning a surface of an optical window includes a first electrode that is provided inside the optical window and is covered with a dielectric material forming the optical window. A second electrode is provided around the optical window and is exposed on at least one surface of the optical window. A power supply is electrically coupled between the first electrode and the second electrode. The apparatus further includes a controller that controls the power supply so as to generate dielectric barrier discharge along the surface of the optical window by applying a high-frequency or pulsed voltage between the first electrode and the second electrode.