Modelling and Diagnostics of a Supersonic DC Plasma Jet Expanding at Low Pressure

A numerical model of an argon jet exiting a LPPS torch has been developed and validated against enthalpy probe measurements for a slightly overexpanded jet at a chamber pressure of 100 mbar. Visualization of the jet using a CCD camera shows the presence of a small Mach reflection in the first compression-expansion cell with only oblique shock waves in the second cell. This jet topology is also observed in the model results. The images of the enthalpy probe on the axis of the plasma jet reveal that the shock layer, or shock-probe distance, varies according to the axial location of the probe. Shock-probe distance can be as large as 3 mm and should be considered when mapping plasma jets. Paper includes a German-language abstract.