Experimental observations of arc-anode attachment in steam-argon-air environment

DC arc plasma torches performance depends strongly on processes near anode. Arc-anode interaction not only defines lifetime of the electrode but also influences power distribution in the plasma and flow structure of the jet. This paper presents an experimental investigation of effects of gas properties and flow conditions on an arc-anode attachment. Several optical and electric diagnostic means were used to provide complex image of behaviour of the attachment and resulting state of anode surface. It is shown that even in one particular regime of the arc-anode attachment, which is called a restrike mode, dynamic behaviour and resulting erosion of anode can be significantly different. For example with argon in arc-anode gap the anode surface melt more intensively than with air environment. Despite increased melting weaker radiation of copper vapour was found in plasma. It was also shown that control of arc-anode attachment position in air environment had substantial effect on anode erosion pattern and plasma flow behaviour.