Generation of long, laminar plasma jets at atmospheric pressure and effects of flow turbulence

Long, laminar plasma jets at atmospheric pressure of pure argon and a mixtu re of argon and nitrogen with jet length up to 45 fi,Hes its diameter could be generated with a DC are torch by! restricting the movement of arc root in the torch channel. Effects of torch structure, gas feeding, and characte ristics of power supply on the length of plasma jets were experimentally ex amined. Plasma jets of considerable length and excellent stability could be obtained by regulating the generating parameters, including are channel ge ometry gas flow I ate, and feeding methods, etc. Influence of flow turbulen ce at the torch,nozzle exit on the temperature distribution of plasma jets was numerically simulated. The analysis indicated that laminar flow plasma with very low initial turbulent kinetic energy will produce a long jet, wit h low axial temperature gradient. This kind of long laminar plasma jet coul d greatly improve the controllability for materials processing, compared wi th a short turbulent are let.