19 research outputs found
Modelling and experiments of non-transferred plasma torches
No full textGreenhouse 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
Modelling and experiments of non-transferred plasma torches [Elektronisk resurs]
No full textGreenhouse 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.</p
Computational Analysis of Flow Separation in Non-Transferred Plasma Torch: Causes, Impacts and Control Methods
No full textIn a non-transferred plasma torch, the working gas becomes ionized and forms plasma as it interacts with the electric arc at the cathode tip. However, in certain cathode shapes, particularly flat ones, and under specific conditions, the gas flow can separate at the cathode tip, forming a vortex region. While this flow separation is influenced by geometric factors, it occurs in the critical zone where plasma is generated. Understanding the causes of this separation is essential, as it may significantly impact torch performance. If the separation proves detrimental, it is important to identify ways to mitigate it. This paper presents a computational analysis of a non-transferred plasma torch to investigate the physics behind flow separation. The results highlight the location and causes of the separation, as well as its potential advantages and disadvantages. Finally, the paper explores theoretical approaches to address flow separation in plasma torches, offering practical insights for enhancing their design and efficiency.Validerad;2025;Nivå 1;2025-02-12 (u8);Full text license: CC BY 4.0</p
The Effect of Non-Transferred Plasma Torch Electrodes on Plasma Jet: A Computational Study
No full textThis study explores how different electrode shapes affect plasma flow in a non-transferred plasma torch. Various cathode geometries—including conical, tapered, flat, and cylindrical—were examined alongside stepped anode designs. A 2D axisymmetric computational model was employed to assess the impact of these shapes on plasma behavior. The results reveal that different cathode designs require varying current levels to maintain a consistent power output. This paper presents the changes in electric conductivity and electric potential for different input currents across the arc formation path (from the cathode tip to the anode beginning) and relating to Ohm’s law. Significant variations in plasma jet velocity and temperature were observed, especially near the cathode tip. The study concludes by evaluating thermal efficiency across geometry configurations. Flat cathodes demonstrated the highest efficiency, while the anode shape had minimal impact.Validerad;2025;Nivå 2;2025-08-06 (u5);Full text license: CC BY 4.0;</p
Numerical Simulation of a Radial Free Surface Liquid Jet Impinging on a Heated Surface
No full textImpinging liquid jets have been demonstrated to be an effective means of providing high heat transfer rates, and widely used in designing cooling systems for electronic modules, plastic manufacturing, and many other applications in the industry. It is very important to study the factors which govern the heat transfer rate in the liquid impingement on a heated surface to ensure cooling efficiency. The paper presents a numerical approach to study the convective heat transfer of circular liquid jet impingement on a heated surface where influencing factors like surface tension, gravity, viscosity, surface temperature etc. are considered. Finite volume method (FVM) with pressure based coupled solver implemented in commercial ANSYS Fluent CFD is used to solve Reynolds Averaged Navier Stokes equations. Free surface flow is modelled using Volume of Fluid (VOF) Method along with the compressive scheme and sharp interface modelling which accurately captures interfaces between immiscible fluids. The liquid film formation and the heat transfer phenomenon are examined in detail. The influence of jet velocity profiles on pressure distribution and heat transfer along the heated surface is presented. The results obtained from numerical solution are validated against experiment and previously published work with a close match.Godkänd;2021;Nivå 0;2021-02-16 (johcin)</p
Computational Modeling Of Turbulent Jet Generated by Non-transferred Plasma Torch
No full textThe plasma jet produced by a non-transferred plasma torch may initially appear steady and laminar, but it undergoes significant turbulence as it interacts with the surrounding atmosphere. Within the plasma torch, the jet begins as laminar; however, upon exiting, it transitions into a turbulent flow, extending into a long, wavy structure as it develops. This paper explores the complexities of computational modeling for non-transferred plasma torches, focusing on the challenges of simulating the multiphysics and multiphase interactions at the outlet and tracing the evolution of the plasma jet. The computational analysis uses COMSOL Multiphysics software on a 2D axisymmetric geometry, with steady-state simulations incorporating various turbulence models. A comparative assessment of the results from each turbulence model is provided, highlighting their respective strengths and limitations. Although the diffusion of the turbulent jet at the outlet is presented, the turbulence models employed in this study only offer time-averaged values, rather than a detailed breakdown of the complete jet structure. The paper concludes by validating the computationally obtained velocity magnitudes against experimental data, ensuring the accuracy and reliability of the simulation results.ISBN for host publication:978-82-536-1866-1</p
Computational Modeling Of Turbulent Jet Generated by Non-transferred Plasma Torch
No full textThe plasma jet produced by a non-transferred plasma torch may initially appear steady and laminar, but it undergoes significant turbulence as it interacts with the surrounding atmosphere. Within the plasma torch, the jet begins as laminar; however, upon exiting, it transitions into a turbulent flow, extending into a long, wavy structure as it develops. This paper explores the complexities of computational modeling for non-transferred plasma torches, focusing on the challenges of simulating the multiphysics and multiphase interactions at the outlet and tracing the evolution of the plasma jet. The computational analysis uses COMSOL Multiphysics software on a 2D axisymmetric geometry, with steady-state simulations incorporating various turbulence models. A comparative assessment of the results from each turbulence model is provided, highlighting their respective strengths and limitations. Although the diffusion of the turbulent jet at the outlet is presented, the turbulence models employed in this study only offer time-averaged values, rather than a detailed breakdown of the complete jet structure. The paper concludes by validating the computationally obtained velocity magnitudes against experimental data, ensuring the accuracy and reliability of the simulation results.ISBN for host publication:978-82-536-1866-1</p
Modelling of heat flow and electromagnetic phenomena in a non-transferred plasma torch
No full textOver the decades, computational methods have been used to model and describe the flow andionization dynamics in plasma torches. However, the impact of the operational parameters such as gas flow rate, swirl number and input current density on flow is still inexplicit. In this study, the flow in a non-transferred plasma torch is modelled using COMSOL Multiphysics, and the influence of these parameters is studied. The analysis is carried out on an axisymmetric geometry with the conical-shaped cathode, nozzle-shaped anode, and Argon is used as the plasma gas. A thermal plasma (equilibrium discharges) is considered, i.e., the plasma is underpartial to complete local thermodynamic equilibrium in which the magnetohydrodynamic (MHD) equations are solved. This is treated in the Equilibrium Discharge Interface in COMSOL’s plasma module that has been used in the present study. The laminar flow analysisis performed for low-velocity cases and turbulent flow analysis for higher velocities. It was found that the velocity increase across the plasma arc due to ionization and gas expansion, couldbe observed only for sufficiently high plasma inflow velocities. The position of the plasma arcis determined for different operating conditions. It was further found that the velocity has anegligible effect on the length of the plasma arc, whereas the dependency of the arc length andattachment point on the anode wall, to the input current density and cathode tip temperature iswell explained. The paper concludes by presenting the variations in temperature and velocityof plasma arc due to swirling inflow.ISBN för värdpublikation: 979-10-96389-13-1</p
