Modelling and experiments of non-transferred plasma torches

Sammanfattning: Greenhouse gases and their negative effects on climate is one of the most discussed topics around the world. Globally, fossil fuel-related emissions from process industries, transportation, and electricity generation are one of the biggest contributors to greenhouse gases. One of the prime questions asked globally is how to reduce these emissions. Plasma burners can be an answer to the question. They are entirely electric-driven burners and operate at high temperatures. Presently, the available burners are small scale due to which they are not applicable in industries. So a substantial amount of interest lies in up-scaling them. However, to begin the up-scaling process, it is fundamental to clearly understand the working of the plasma burner and the various factors that affect its operation. The present thesis explains the working of a plasma burner under different operating conditions is studied experimentally, computationally, and the obtained results are validated with theoretical data. Experimentally, the temperature measurements at the plasma torch outlet were carried out using optical spectroscopy. The velocity and structure of the plasma jet coming from the outlet were studied using a high-speed camera. The experimental measurements were carried out for varied input working gases, velocities, and powers. The computational analysis was perfomed using COMSOL multiphysics software. The primary modeling was done using the equilibrium discharge interface model (EDI) in which plasma is considered to be fully ionized and at local thermal equilibrium. But considering the drawbacks of the EDI model, further computational analysis was initiated by modeling weakly ionized plasma. Different geometries of the plasma torch, working gases, velocities, and power are analyzed computationally. Further, the experimental and computational results are validated with each other and thermodynamic equilibrium data obtained using the TEC program. Finally, this thesis promises to give an overview of the plasma torches, their working under different operating conditions, and a brief discussion about the future focusing on up-scaling the plasma burners.