Studies of vortex characteristics and gas-dynamic fields in Ar-H₂ inductively coupled plasma

Numerical simulation of a technical RF inductively coupled torch of Ar-H₂ plasma were made with five turns and under a variation of H₂ mole fraction from 0 to 20%. The coupled power and generator frequency varied in the range from 4 to 16 kW and from 1 to 10 MHz, respectively. The gas dynamic fields were compared with experimental and numerical results. The presence of frontal and stern vortices on the upstream and downstream sides of discharge zone was analysed. The differences in the vortex flow patterns and gas-dynamic fields under different H₂ mole fractions, coupled powers and generator frequencies were compared. Special attention was paid to investigate the transition conditions of the frontal vortex from Benard to toroidal, as well as the conditions to sweep away the stern vortex. Two different methods have been applied to penetrate the frontal vortex. The critical flow rates of central and outer gases have been determined under different H₂ mole fractions, coupled powers and generator frequencies. The choice about the injection probe position to penetrate the frontal vortex in Ar-H₂ plasma with different gas compositions has been discussed. The dependences of the vortex intensity on the generator frequency and H₂ mole fraction under different coupled powers have been established.