In this work, plasma flow inside a cascaded DC torch, effect of a plasma gas composition (Ar or CO2+CH4), and torch performance were studied. Both laminar model and k-ε turbulence model were employed and compared in the simulations. The results revealed that carbon contained gases can significantly increase the arc voltage and torch power. This gas mixture increases the arc voltage by up to 200% in comparison with argon. Voltage-current characteristics were also simulated for the current range of 200-400A. Differences in the torch performance can be attributed to the gases specific properties. For instance, at the same temperature the considered plasma gases have similar electric conductivities but the enthalpy of molecular CO2+CH4 is much higher. Experimental validation indicates that k-ε turbulence model provides better agreement.