How to Ignite an Atmospheric Pressure Microwave Plasma Torch without Any Additional Igniters
April 16th, 2015
This movie shows how an atmospheric plasma torch can be ignited by microwaves with no additional igniters and provides a stable and continuous plasma operation suitable for plenty of applications.
The overall goal of this procedure is to obtain a microwave plasma torch, which provides ignition without any additional igniters, as well as stable and continuous operation. This is accomplished by first measuring the frequency dependence of the magnetron. The second step is to adjust the resonance frequency of the coaxial resonator of the microwave plasma torch to the sending frequency of the magnetron.
Next, maximize the forward microwave power by adjusting the stubs of the three stub tuner. The final step is to mount the adjusted microwave plasma torch system to the priorly measured magnetron. Ultimately, when the microwave power is supplied, the plasma ignites and can be operated stably and continuously.
This method provides insight into the ignition process and operation of a microwave plasma torch. It can also be applied to other systems such as microwave micro plasma jets. Begin by preparing the magnetron.
This video begins with the magnetron connected to an insulator with a circulator and a water load. The insulator is connected to a directional coupler, which is connected to a second water load before proceeding supply all water loads with water. Next, turn attention to the spectrum analyzer.
Connect a 20 decibel attenuator to protect the analyzer. When power exceeds one watt, then get a coaxial cable. The cable should have a BNC connector at one end and an end connector at the other.
Connect the BNC end to the attenuator and extend the cable to the directional coupler. Connect the end connector of the coaxial cable to the directional coupler. This schematic provides an overview of the equipment connections at this point.
Now switch on the magnetron and view the spectrum on the spectrum analyzer Display. Proceed to measure the frequency of the output as a function of the microwave power. Do this by increasing the microwave power from 10%to 100%of its maximum output power in increments of five to 10%of maximum power.
For every step, determine the frequency of the maximum amplitude displayed on the spectrum analyzer. The measured frequency dependence of the magnetron is given in this diagram. After completing the measurement, shut off the power and the water supply.
Then remove the directional coupler and the second water load, leaving the magnetron and insulator connected. Once the spectrum of the magnetron has been measured, begin working with the microwave plasma torch assembly and the network analyzer. The plasma torch assembly is connected to a three stub tuner, which is connected to a coaxial rectangular transition.
Use a network analyzer with an appropriate measuring cable equipped on one end and an end connector on the other. Connect the analyzer via the end connector to the coaxial rectangular waveguide transition. This schematic gives the final configuration of the equipment for adjusting the resonance frequency and the forward power.
Switch the network analyzer to VSWR or log mode and S one one operation. To monitor the resonance frequency, observe the dip of the S one one parameter, which marks the resonance frequency of the microwave plasma torch assembly. Prepare to adjust the dip position by moving the nozzle of the plasma torch assembly.
Make iterative adjustments to the nozzle to set the resonance frequency. Set the resonance frequency to the measured frequency of the magnetron at 25 to 60%of its maximum output power. Then lock the position of the nozzle with the locking nut.
Next work to increase the forward microwave power by iteratively adjusting the stubs of the three stub tuner. Use the depth of the S one one parameter for feedback. The aim is to maximize its depth for safety.
Perform plasma ignition under local gas ventilation and wear UV glasses. The apparatus for the experiment is located on the right. For the experiment.
The microwave plasma torch assembly and the three stub tuner are connected to the circulator and magnetron. As in this schematic, the gas supply is being connected to the microwave plasma torch. The magnetron and insulator are located in the back, but not pictured.Here.
Turn on the gas supply to five to 20 standard liters. Air per minute, turn on the microwave to 10%of maximum power, and then and ensure that there are no microwave leaks. Hold a mirror to monitor plasma ignition in the quartz tube and begin to slowly increase the power while monitoring the ignition of the plasma.
Stop increasing the power when ignition has occurred. When the plasma burns in the cylindrical mode, adjust the tuner so that all of the microwave power is absorbed by the plasma. Now adjust the extent of the plasma by varying the microwave power.
Note, the plasma must not touch the quartz tube. A camera at 1000 frames per second captured images of microwave plasma ignition through the diagnostic slit portions of the coaxial resonator nozzle tip and the cylindrical resonator before ignition are labeled for orientation. The microwave power is one kilowatt and the gas flow is 15 standard liter air per minute.
The plasma ignites in the coaxial resonator. The plasma then winds up the metallic nozzle to its tip and begins to burn straight in the coaxial mode. As time goes on, the intensity of the plasma grows until there is a shift in the resonant frequency due to the burning plasma in the coaxial resonator.
At this point, the plasma starts to break away from the nozzle tip. After complete breakaway, the plasma burns freely above the metallic nozzle. In cylindrical mode, the stubs of the three stub tuner are readjusted to the complete power absorption by the plasma.
The dimensions of the plasma depend on the supplied microwave power and the gas flow. As this comparison demonstrates for the same microwave power, an increase in gas flow leads to a decrease in plasma asthma for the same gas flow. An increase in microwave power leads to an increase of plasma.
After watching this video, you should have a good understanding of how the ignition and operation after presented microwave plasma touch works.
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Overview
This movie demonstrates the ignition of an atmospheric plasma torch using microwaves without additional igniters, ensuring stable and continuous plasma operation suitable for various applications.
Key Study Components
Area of Science
- Plasma Physics
- Microwave Technology
- Atmospheric Plasma Applications
Background
- Microwave plasma torches are used in various industrial applications.
- Stable plasma operation is crucial for efficiency and effectiveness.
- Traditional ignition methods often require additional components.
- This study explores a method to ignite plasma using microwaves alone.
Purpose of Study
- To develop a microwave plasma torch that ignites without additional igniters.
- To achieve stable and continuous operation of the plasma torch.
- To optimize the system for various practical applications.
Methods Used
- Measure the frequency dependence of the magnetron.
- Adjust the resonance frequency of the coaxial resonator.
- Maximize forward microwave power using a three stub tuner.
- Mount the adjusted microwave plasma torch system to the magnetron.
Main Results
- The microwave plasma torch ignites successfully without additional igniters.
- Stable and continuous plasma operation was achieved.
- The system can be optimized for various applications.
Conclusions
- This method simplifies the ignition process for plasma torches.
- Stable operation enhances the usability of microwave plasma technology.
- Further applications can be explored with this innovative approach.
