Generation of thermal plasma jets in liquid-stabilized and hybrid gas-liquid plasma torches

Plasma torches with liquid-stabilized arcs provide an alternative to commonly used sources of thermal plasmas based on gas-stabilized arcs or RF discharges. Relatively long arc columns can be stabilized by liquid walls under very low plasma mass flow rates. This leads to high values of plasma temperature and enthalpy. In water-stabilized torches, oxygen-hydrogen plasma jet is produced with extremely high plasma enthalpy and flow velocity. Plasma torches with water-stabilized arc provide special performance characteristics in some plasma processing applications like plasma spraying or waste treatment. A new type of hybrid torch is based on combination of principles of liquid and gas arc stabilization and offers possibility of control of plasma jet characteristics in a wide range from values typical for liquid-stabilized torches to values typical for gas-stabilized torches. Physical processes that determine properties of generated plasma are discussed and basic characteristics of water and hybrid torches are presented in the paper. (author)