Capillary Spray Electrode with Dielectric Coating for Single-Jet Stability
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Solution Overview
Problem
Existing electrostatic spraying devices face challenges in consistently predicting and controlling the direction and spread of liquid droplets across different formulations, often resulting in multiple jets due to variations in electric field geometry and liquid properties, making them impractical for commercial applications.
Innovation Solution
The design of a capillary spray electrode with a focused electric field at a single point, achieved through modifications such as a projection or bevel at the spraying end, and a dielectric or semiconductor coating to inhibit multiple jet formation and corona, along with a method for cleaning the electrode using pulsed pressure waves to maintain performance over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional capillary spray electrode is used, then the device can spray liquid, but multiple jets are formed due to variations in electric field geometry and liquid properties, making the device impractical for commercial applications
Solution Approach 1:
The spray electrode incorporates a dielectric coating applied locally at the spray aperture region, creating a non-uniform electric field distribution that focuses the field at a single point. This local modification of the electrode surface properties prevents multiple jet formation while maintaining spray functionality across different liquid formulations.
Solution Approach 2:
The dielectric coating changes the electrical parameters of the spray electrode surface, specifically modifying the electric field distribution and breakdown voltage characteristics. This parameter change stabilizes the spray pattern by ensuring single-jet formation regardless of variations in liquid properties or flow rates.
2Reliability
If the electric field is strengthened to prevent multiple jets, then single-jet formation is achieved, but corona discharge occurs causing electrode degradation
Solution Approach 1:
A dielectric coating is introduced as an intermediary layer between the conductive spray electrode and the liquid spray. This intermediate layer modifies the electric field distribution, allowing single-jet formation at lower voltages and preventing corona discharge by distributing the electrical stress more evenly across the spray aperture.
Solution Approach 2:
The dielectric coating transforms the potentially harmful concentrated electric field that causes corona discharge into a beneficial focused field that produces stable single-jet spray. The coating converts the harmful high-field-stress condition into a controlled field distribution that maintains spray stability without causing electrode degradation.
3Reliability
If the spray electrode is modified to focus the electric field, then single-jet formation is achieved, but the device complexity increases
Solution Approach 1:
The dielectric coating is applied as a thin, inexpensive layer that can be deposited on the spray electrode using simple coating techniques. This approach adds minimal complexity to the electrode structure while achieving the desired spray stability, making the modification cost-effective and easy to implement.
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 ensures a robust and consistent single-jet formation, reducing sensitivity to formulation changes and extending device lifespan by preventing multiple jet formation and corona-related degradation, thus enhancing operational efficiency and reliability.
Implementation Method 1
the electrodes being connected, in use, across a generator in order to establish an electric field between the electrodes and cause fluid in the capillary to be sprayed from the spray electrode
Implementation Method 2
electrostatic spraying device for the atomisation and vaporization of chemicals through the generation of a high specific surface of a liquid
Implementation Method 3
a dielectric or semiconductor coating to inhibit multiple jet formation and corona
Implementation Method 4
a method for cleaning the electrode and a device for performing the method... applying a pulsed pressure wave to the fluid as it is sprayed from the spray electrode, thereby cleaning the spray electrode
Data Source
AI summary
An electrostatic spraying device comprises a capillary spray electrode having a spraying end, a reference electrode, and a reservoir in fluid communication with the spray electrode. In use, the electrodes are connected across a generator in order to establish an electric field between the electrodes and cause fluid in the reservoir to be sprayed from the spray electrode. The spray electrode has a focus that defines a point at which the electric field is focussed on the spraying end.