Modeling of the arc characteristics inside a laminar spraying plasma torch with different gas components

Abstract

For the low costs, numerical simulations are effective methods to reveal the internal mechanism inside thermal spraying plasma torch. Various simulation models for studying the inside or outside characteristics of thermal plasma torches have been built and discussed. However, for revealing the mechanism in the materials processing, more attentions should be paid to building precise models of laminar plasma torch and using these models to reveal the generating mechanism and the flow characteristics. Thus, based on the user-defined function (UDF) and user-defined scalar (UDS) of ANSYS Fluent software, the assumptions, governing equations, boundary conditions and solving method were discussed and a corresponding numerical model of a home-made laminar spraying plasma torch was built firstly. For verifying the effectiveness of the proposed numerical model and studying the influence of the gas components on the arc characteristics, the working conditions and experimental setups were introduced in sequence. Finally, the numerical and experimental results of the home-made laminar plasma torch were obtained and discussed. The study results show that: ¬① The axial temperature of the plasma torch could be divided into three sections along the axis: peak temperature area (10mm < x < 20mm), stable temperature area (20mm < x < 62mm) and decrease temperature area (62mm < x < 95mm). ② The axial velocity of pure nitrogen is much higher than that of pure argon and 50%Ar + 50%N2, while that of pure argon and 50%Ar + 50%N2 has a little difference. ③ The simulated arc voltage trends under different working conditions are in accordance with the experimental arc voltage trends well.