要約

In order to characterize the working regime of an argon plasma torch we measured and analysed by fast Fourier transform (FFT) the four following parameters : torch voltage, torch current, net radiative power emitted by the plasma jet, and noise (acoustic pressure) emitted by the torch. At high flow rate we observed a turbulent behavior characterized by a high correlation voltage -acoustic pressure or at lower flow rate a broad band spectrum whose global amplitude decreases with flow rate. These behaviors are attributed to the fluctuations of the arc root position. At low flow rates we observed in the acoustic pressure spectrum a narrow peak whose frequency decreases with flow rate and whose maximum amplitude coincides with turbulent laminar transition. We suggest these acoustic pressure fluctuations could result from the electric self oscillations of the arc. We give some results for other types of gases.