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High-speed imaging in plasma arc cutting: a review and new developments
No full textThe aim of this paper is twofold: (i) to review all the achievements in our understanding of the phenomena related to plasma arc cutting (PAC) technology by means of high-speed camera (HSC) imaging and flow visualization techniques and (ii) to report on new studies that make use of recent and advanced instrumentation for HSC diagnostics, also highlighting some previously uncovered research subjects. In the last decade HSC imaging and flow visualization techniques have progressed considerably as a powerful qualitative diagnostic technique for investigating some of the fundamental phenomena typically occurring in PAC technology. More recently, HSC imaging has also been used to investigate pre-cut phases in PAC analysis, such as pilot arcing and piercing of mild steel and stainless steel plates with dual gas torches in various operating conditions, providing new insight into the process and highlighting some interesting plasma behaviour. HSC imaging of pilot arcing has been used to investigate the influence of the arc current, plasma pressure and swirl strength on the shape of the arc, on the type of the rotational motion of its attachment on the nozzle tip and to track trajectories and velocities of hafnium particles emitted from the electrode insert during that phase. HSC imaging can also highlight the behaviour of the arc during piercing phases and the possible presence of short non-destructive double arcing, otherwise impossible to recognize
MODELLING AND COMPARISON OF DIFFERENT DESIGN SOLUTIONS AND EXPERIMENTAL RESULTS FOR DC TRANSFERRED ARC PLASMA CUTTING TORCHES
No full textThe 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
High Speed Imaging of Pilot Arcing and Piercing in PAC
No full textIn this paper, high-speed camera imaging of pilot
arcing and piercing process phases in plasma arc cutting (PAC)
with dual gas torches have been investigated using mild-steel and
stainless-steel plates. 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 nonperfectly aligned consumables (shield-nozzle) on inducing
destructive piercing
Torcia al plasma
No full textIl presente trovato concerne una torcia al plasma ad arco trasferito per il taglio dei materiali metallici con elevate caratteristiche di durata degli elementi operativi e con innovazioni nella gestione del gas secondario
Understanding Plasma Fluid Dynamics Inside Plasma Torches Through Advanced Modeling
No full textThe aim of this paper is to investigate the behavior of
different types of transferred-arc dual-gas plasma torches used for
the cutting of metallic materials bymeans of a 2-D FLUENT-based
numerical model, putting into evidence the physical reasons for
the industrial success of various design and process solutions
appeared over the last years, such as the following: vented-nozzle
technology, various different approaches for the geometry of the
plasma chamber, the effect of externally superimposed magnetic
fields, and secondary-gas-swirl injections with different directions.
Flow and heat-transfer equations are solved with coupled electromagnetic
ones for local-thermodynamic-equilibrium optically thin
plasma, whereas turbulence phenomena are taken into account
by means of a κ−ε realizable model. The simulations include
a prediction of the thermal behavior of the solid components
of the torch head, including electrode and hafnium insert, and
the efficiency of nozzle- and electrode-cooling systems in various
operating conditions, including gas mixtures (O2/air, H35/N2,
and N2/N2). Radiation is included in the calculation of heat
transfer to the surfaces of the components, using a customized
discrete-ordinate model. Results have been analyzed with respect
to plasma behavior, and conclusions have been drawn, concerning
the powerfulness of numerical simulation as a tool for cutting
torch design
Metodo per la realizzazione di un elettrodo per torce al plasma ed elettrodo così realizzato
No full text- …
