Five turbulence models of Reynolds average Navier-Stokes (RANS),including the standard k-ε model,the RNG k-ε model taking into account the low Reynolds number effect,the realizable k-ε model,the SST k-ω model,and the Reynolds stress model (RSM),are employed in the numerical simulations of direct current (DC) arc plasma torches in the range of arc current from 80 A to 240 A and air gas flow rate from 10 m3 h-1 to 50 m3 h-1.The calculated voltage,electric field intensity,and the heat loss in the arc chamber are compared with the experiments.The results indicate that the arc voltage,the electric field,and the heat loss in the arc chamber calculated by using the standard k-ε model,the RNG k-ε model taking into account the low Reynolds number effect,and the realizable k-ε model are much larger than those in the experiments.The RSM predicts relatively close results to the experiments,but fails in the trend of heat loss varying with the gas flow rate.The calculated results of the SST k-ω model are in the best agreement with the experiments,which may be attributed to the reasonable predictions of the turbulence as well as its distribution.