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Experimental Study of Plasma Effect on Penetration Flame for Non-Premixed Mixtures of Air and Low Calorific Value Fuels

Nourmohammadi, Mohammad Saeed | 2023

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 57481 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Mardani, Amir
  7. Abstract:
  8. This project investigates the effect of plasma on diffusion flame. A Dielectric Barrier Discharge (DBD) plasma actuator has been used to generate plasma, which converts fuel-air non-premixed mixtures into plasma. Then, the effect of plasma on the shape and stability of the diffusion flame composed of fuel and air mixture has been evaluated. This study investigates the laminar flow regime for low calorific value fuels. For this purpose, natural gas fuel (urban methane) has been diluted with N2 and CO2 gases to reduce its calorific value. Then, the diffusion flame is formed from the fuel and air mixture in a laboratory stand. This stand consists of two coaxial tubes made of quartz, fuel flows from the inner tube and air from the outer tube. This study uses the DBD (Dielectric Barrier Discharge) operator to create plasma in fuel-air mixtures in a non-premixed state. For this purpose, two coaxial tubes made of quartz are used as dielectric and two metal rings as electrodes. A metal rod is located in the center of the inner tube and the fuel passes through it. Air flows through the outer tube, and mixes with the fuel outside the tube. The penetrating flame is formed from this mixture and photographed with a digital camera. Narrow-band imaging filters at 430-470-610 wavelengths are used for higher accuracy. This study examines the effect of plasma on the diffusion flame diluted with CO2 and N2 gases. Plasma has been induced using the DBD (Dielectric Barrier Discharge) operator in two modes of ionization from the fuel side and ionization from the air side. According to the results, if the plasma induction distance to the fuel nozzle is less than 8 mm, the plasma can reduce the flame length in both cases. Otherwise, the plasma will increase the length of the flame. Also, the plasma causes the rising flame to stick to the nozzle.The effects of DBD plasma operator on the penetrating flame structure for fuel mixtures with low calorific value and air diluted with N2 and CO2 gases and experimental tests on the methane molecule and the phenomena occurring due to plasma injection in the combustion field have been done. The effect of fuel ionization as well as the effect of electrode spacing on the flame regime have been studied. Also, the effect of the output power of the plasma actuator and the stability of the penetrating flame with plasma injection in the combustion area have been investigated. Data collection using thin band filters that pass a small part of the light wavelengths, the phenomena occurring in the combustion have been studied. Plasma causes a change in the flame speed field at the ionization site, and this change in the speed field causes the flame to oscillate and the flame intensity increases to a great extent with the presence of plasma. Also, the use of the plasma operator has a very significant effect on the return of completely separated flames, and it can be used to prevent combustion in high-speed engines, such as the Eskerjet. By applying plasma, the fuel can be diluted to nearly 1 0 percent compared to the non-applied state The plasma increased without the flame rising and leaving the bit. Adding carbon dioxide as a diluent to the fuel flow creates a more unstable flame than nitrogen, and therefore, in the case of dilution with carbon dioxide, the flame goes out sooner. The flame is out of steady state without fluctuation and many fluctuations occur in the flame, which is a sign of the change of the velocity field at the ionization site
  9. Keywords:
  10. Plasma ; Dielectric Barrier Discharge (DBD) ; Plasma Actuator ; Non-Premixed Flame ; Combustion ; Plasma Assisted Combustion (PAC)

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