Experimental investigation of up stepped and down stepped labyrinth seals was made to study the effects of the pressure ratio of inlet and outlet and relative axial location of step and labyrinth on leakage characteristics at rotational and static states.The results show that the sealing characteristics of both up stepped and down stepped labyrinth seals are similar.The leakage coefficient increases with the increase of the pressure ratio.At given inlet total pressure and total temperature

the pressure distribution along the sealing passage decreases almost linearly.The leakage is almost unchanged with variation of the step axial location or the low rotating speed in the experimental range.