A NEW NOZZLE DESIGN FOR DC PLASMA SPRAY GUNS

A new design is proposed for dc plasma spray gas shroud attachments. I t has been found experimentally that the performance of a conventional conical gas shroud is not satisfactory due to the entrainment of the cold air inside the gas shroud. Numerical simulations confirmed this f inding. Parameters such as the cone angle and the main gas flow rate c an significantly influence the flow pattern inside the nozzle, resulti ng in air entrainment and formation of a circulation zone at the exit region. A new design is proposed which can considerably improve the pe rformance of shrouded nozzles. The superior performance of the propose d design has been demonstrated by numerical simulation. The new design is based on a modification of the conical shape by optimizing the pro file of the nozzle from a conical shape with a constant angle to a str eamlined configuration. The optimized shape was obtained from an analy sis of the streamlines of fixed angle nozzle.