MODELLING AND COMPARISON OF DIFFERENT DESIGN SOLUTIONS AND EXPERIMENTAL RESULTS FOR DC TRANSFERRED ARC PLASMA CUTTING TORCHES

Document Type : Original Article

Authors

1 Full Professor, Department of Mechanical Engineering (D.I.E.M.), Alma Mater Studiourum-Università di Bologna, Italy.

2 PhD Student, Department of Mechanical Engineering (D.I.E.M.), Alma Mater Studiourum-Università di Bologna, Italy.

3 Researcher, Department of Mechanical Engineering (D.I.E.M.), Alma Mater Studiourum-Università di Bologna, Italy.

4 Director of the technical staff, Cebora S.p.A., Cadriano di Granarolo, Italy.

5 Team leader Plasma Cutting Division, Cebora S.p.A., Cadriano di Granarolo, Italy.

Abstract

ABSTRACT
The aim of this work is mainly to investigate by means of a 2-D FLUENT©
based
numerical model the behaviour of different types of transferred arc dual gas plasma
torches used for cutting of metallic materials, giving the physical reasons for the
industrial success of various design and process solutions appeared over the last
years. Flow and heat transfer equations are solved with coupled electromagnetic ones,
for an optically thin LTE plasma, while turbulence phenomena are taken into account by
means of a k-ε RNG model, including the prediction of thermal behaviour of the solid
components of the torch head and the efficiency of nozzle and electrode cooling
systems in various operating conditions including gas mixtures (O2/air, H35/N2, N2/N2).
Radiation is included in the calculation of heat transfer to the surfaces of the
components using a customized Discrete Ordinate (DO) model. Additional experimental
results have been obtained using a high speed camera (HSC), during pilot arcing and
piercing of mild and stainless steel plates of various thickness and in different operating
conditions. The technique has provided new insight of the PAC process and some
interesting phenomena have been highlighted: such as, the trajectory and velocity of
hafnium particles emitted from the electrode during pilot arcing and the effect of non
perfectly aligned consumables (shield-nozzle) on inducing destructive piercing.

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