Abstract: Three-dimensional Reynolds-averaged Navier-Stokes(RANS) equations were numerically solved to investigate the influence of the inlet preswirl on discharge and heat transfer characteristics in honeycomb and smooth labyrinth seals.The discharge and total temperature increase characteristics,as well as the leakage flow field of these two different seals,were also obtained under five different pressureratios at inlet preswirl ratios of-0.3,0,+0.3.The results show that the influence of the inlet preswirl on the leakage flow rate and meridian flow structure is nearly negligible for both honeycomb and smooth labyrinth seals.Positive inlet preswirl can decrease the total temperature difference between the seal inlet and outlet,while the negative preswirl will cause the opposite effect.The damping effect of the honeycomb can reduce the influence of the inlet preswirl on the total temperature difference.The computed windage heating power of the honeycomb seal is larger than that of smooth labyrinth seal with positive or without inlet preswirl,while it's smaller for the negative inlet preswirl condition.