# The Effect of Non-Transferred Plasma Torch Electrodes on Plasma Jet: A Computational Study  
[PERSON]  
1 Division of Fluid and Experimental Mechanics, Lulea University of Technology, SE-971 87 Lulea, Sweden;  
1 [EMAIL_ADDRESS] (L.-G.W.);  
1  
[PERSON]  
1 Division of Fluid and Experimental Mechanics, Lulea University of Technology, SE-971 87 Lulea, Sweden;  
1 [EMAIL_ADDRESS] (L.-G.W.);  
1 [EMAIL_ADDRESS] (H.O.A.)  
1 hans.akrested@  
the characteristics, RTC-based torches are commonly used in material processing, plasma welding, thermal spraying, and synthesis applications [6].  
In an RTC plasma torch, controllable parameters, such as electric current, gas flow rate, gas composition, working gas type, and nozzle geometry, significantly affect non-controllable outcomes such as arc voltage, arc fluctuations, arc length, torch efficiency, and electrode erosion patterns [7; 8]. The effects of gas flow rate, electric current, and gas composition were analyzed in our previous studies [9; 10]. In this work, we focus on how cathode and anode geometries influence arc formation, plasma jet temperature and velocity, and the overall efficiency of RTC-based non-transferred plasma torches for different geometries.  
In a plasma torch, the cathode and anode are the two key electrodes that define arc behavior. The cathode acts as the electron source for sustaining the arc discharge, absorbing heat, and emitting electrons via thermionic emission. RTC torches can use various cathode tip shapes, such as conical, tapered, and flat tips, which influence arc stability and heat transfer. Numerous studies have explored these geometries separately; for example, flat cathodes were modeled by [PERSON] et al. and [PERSON] et al. [11; 12], while tapered cathodes were analyzed by [PERSON] et al., [PERSON] et al., [PERSON] et al., [PERSON] et al., [PERSON] et al., [PERSON] et al. [13; 14; 15; 16; 17; 18; 19], and conical cathodes were investigated by [PERSON] et al. [20; 21]. Although prior work shows that plasma jet velocity and temperature trends are generally similar across cathode shapes, the geometry still affects voltage at the cathode tip, arc formation, flow structure, and torch efficiency. Likewise, the geometry of the anode nozzle influences the location of the arc attachment, the velocity of the plasma jet, the energy efficiency, and air entrainment. [PERSON] et al. found that the way electric power is delivered to the anode significantly affects efficiency [7]. [PERSON] et al. demonstrated that stepped anodes reduce air entrainment compared to cylindrical ones [22].  
The overarching goal of our research is to scale plasma burners to industrial throughput. Achieving this requires a systematic evaluation of the operating parameters that govern torch performance. In particular, electrode geometry is known to modulate arc attachment, energy transfer, and jet stability, all of which ultimately dictate thermal efficiency and longevity. In this study, we therefore perform a computational investigation of how selected cathode and anode shapes influence plasma-jet behavior in an RTC non-transferred torch. The results provide design guidance for selecting electrode profiles that are better suited to scale.