Abstract
To accurately simulate the plasma arc (PA) behavior in a wide current range, a steady two-dimensional model for the numerical calculation of the axisymmetric PA considering the high temperature cathode region (HTCR) was proposed. Based on the experimentally measured HTCR area, two distribution forms, namely, the mean value method and the Gaussian distribution method, were used to simulate the current density distribution behavior in the tungsten tip. The two proposed current densities were compared with the average current density model with a fixed discharge region. The Gaussian distribution form was chosen after a comprehensive comparison of experimental measured data and simulation data in aspects of arc pressure, electron temperature, and arc voltage at a welding current of 120 A. The model was verified to be accepted in a current range of 110–170 A by comparing the simulated and measured peak arc pressure values. The model has higher prediction accuracy over the common plasma arc model with the unchanged tip cathode, extends the prediction current range, and provides a tool for optimizing the nozzle structure and process parameters.
Highlights
The plasma arc has advantages in aspects of high-density heat and powerful arc pressure, and it plays an important role as a heat source in modern metal materials processing, including additive manufacturing,[1] welding,[2] metal sheet flexible forming,[3] materials manufacturing,[4,5] and waste gasification treatment.[6]
Pan et al.[14] established a mathematical model of a tungsten electrode coupled with the plasma and anode and analyzed the heat transfer and flow behaviors in the weld pool on plasma arc welding (PAW)
In the numerical analysis of PA, previous studies assumed that the tungsten tip was a cone with a platform, the current was emitted from the platform in a uniform form, and the cathode area remained constant at different welding current levels.[23,24]
Summary
The plasma arc has advantages in aspects of high-density heat and powerful arc pressure, and it plays an important role as a heat source in modern metal materials processing, including additive manufacturing,[1] welding,[2] metal sheet flexible forming,[3] materials manufacturing,[4,5] and waste gasification treatment.[6]. Pan et al.[14] established a mathematical model of a tungsten electrode coupled with the plasma and anode and analyzed the heat transfer and flow behaviors in the weld pool on plasma arc welding (PAW). Li et al.[15,18] did a lot of research studies on PAW numerical simulation They established the transient and steady models of scitation.org/journal/adv the coupled PA and the weld pool, analyzed the heat transfer and flow phenomena, and later established a model with a stable keyhole to reduce the calculation cost.[16,17]. The inner nozzle wall temperature was set as a constant temperature,[23,24] and the influence of arc heat generation and heat transfer of cooling water on the wall temperature was not considered These simplifications cannot reflect the actual arc process, so it is difficult for the previous model to accurately predict the arc behavior in a wide range of process parameters
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