Abstract: In order to study the influence of the torch constriction on the thermal efficiency

and then to guide the design of laminar plasma torch

the arc voltage and thermal efficiency of two laminar plasma torches with different constriction

working with the same working parameters

were obtained by experiments. Based on the experimental results

the arc voltage and thermal efficiency of the two plasma torch were compared and analyzed. The results show that: working with pure Nitrogen

although the arc voltage of the segmented anode laminar plasma torch (MEPT) is much higher than that of the conventional laminar plasma torch (TEPT)

the thermal efficiency of MEPT is much lower than that of TEPT.