Design and Construction of Atmospheric Pressure Air Plasma Source

SUPERVISOR SUBMITTED BYDr. MAMUNUR RASHID TALUKDER S. Mridul Kanti SahaPROFESSOR, DEPARTMENT EXAM ROLL: 07044922 OF APPLIED PHYSICS AND REG.NO: 1411ELECTRONIC ENGINEERING, SESSION: 2006-07RAJSHAHI UNIVERSITY, YEAR EXAM: 2010 RAJSHAHI.

M.Sc. Thesis Submitted to the Department of Applied Physics and Electronic Engineering, University of Rajshahi.

Goals:

• Aim to generate non-thermal plasma using air as reactant gas

• Design and construction of atmospheric air pressure plasma source- low power- economic- energy efficient

Motivation

• What is Plasma?• Definition of Plasma:• Generation of Plasma: • Design of Atmospheric Pressure Air Plasma

Source:• Recent and Potential Future Applications:

What Is Plasma?

Plasma is the 4th state of matter by Crookes in 1879

States of matter

Ancient View Earth, Water, Wind, Fire Modern View Solid, Liquid, Gas, Plasma

Plasma..the 4th State of Matter

State of matter versus temperature

Solid

Liquid

Gas

Plasma

102 103 104 105 Temperature (°K)

0.01

Particle Energy (eV)

0.11 10

Definition of Plasma

• A plasma is a ionized gas with equal numbers of positive and negative charges.

• A more precise definition: a plasma is a quasi-neutral gas of charged and neutral particles which exhibits collective behavior.

• Examples: Sun, flame, neon light, etc.

Generation of Plasma

• the DC (direct current) and low frequency discharges

• the plasmas which are ignited by radio frequency waves; and

• the microwave discharges.

Functional block of atmospheric pressure air plasma Source

AC Line

DC Power Supply

Converter Circuit

Plasma Discharge Chamber

• DC Supply• Converter Circuit• Electrodes• Discharge Chamber

DC Supply

• Constructed a 24 V DC power supply capable of supplying 3.0 A

• used as 8200 mF 50V capacitor for dc filter

Converter Circuits• Ability to change DC voltages without a transformer• Examples: Boost and buck and flyback circuits

We choose flyback converter because- uses a coupled inductor to act as an isolation transformer and for energy storage- input and output grounds are isolated- voltage Step-down or Step-up by duty cycle and turns ratio- easy to implement of multiple outputs - not need a separate output inductor- best suited for lower power levels

Flyback Converter• uses a transformer as an inductor to store energy

from the magnetizing current • released magnetizing current in a tightly coupled

secondary winding when the input is open-circuited

• primary is prevented from saturating by an air gap in the transformer core

• the output voltage is a function of the turns ratio, and the ratio of the on time to the period t/T:

where T is the period

Electrodes

• discharge produced between two wire electrodes: one anode and other cathode electrode

• cross section area of each electrode is 2.6268 mm2

• spacing between the electrodes has been varied from 0.5 to 3.0 mm

Discharge Chamber

• constructed from 0.35 inch (9 mm) ID stainless steel tube

• having six ports: three on one end plate and rest three on the other end plate

• transparent 4 mm width glass using as end view photos

Computer

Discharge Chamber

Vacuum Pump

Plasma Power Supply

Spectrophotometer (USB2000+XR1)

Pressure Gauge

Cathode

Plasma

Schematic diagram of air plasma source

Electrical Breakdown of Air

• Paschen’s law expressed as

se

b

dpA

dpBV

11lnln.ln

.Vb = breakdown voltage p = process pressured = gap distance between the electrodes γse = secondary ionization coefficient of reactant gas (air)A = constant = 15 cm-1 Torr-1 (for air )B = constant = 365 V cm-1 Torr-1 (for air)

Result

• spacing between the electrodes has been varied from 0.5 to 3.0 mm

• breaks down air at pressure of 760 Torr• rough estimation of secondary voltage and

current is 5 kV and 50 mA• operating frequency at 20 KHz• produced plasma used by other Lab member for

measuring plasma parameters using spectroscopic diagnostics

Applications

• designed Plasma source produced arc plasma• having both recent and potential future

applications of arc plasma technology

Recent Applications-Space Programs-Waste Disposal-Remediation of Radioactive Waste

Continued…

Potential Future Applications- Animal Carcass and Animal Waste- Agricultural Waste- Paper and Pulp Industry Waste- Carpet Disposal- Soil in Situ (borehole) Vitrification- Coal Gasification

Conclusion

• a small purple arc (ne = m-3) produced

between the two electrodes• producing a hissing sound in this arc which

associated its frequency• measured parameters (using this arc)

indicating this source having various eco-friendly applications

104.6 22

Thanks to All