Numerical and experimental investigation of pressure loss and critical sealing characteristics of straight-through labyrinth seal has been made.The results show that the RNG k-ε turbulence model is suited to predict the flow of labyrinth seal.The flow of the last tooth is choked when the pressure ratio between the upstream and downstream of the labyrinth seal reaches a critical value.With the increase of the pressure ratio the critical cross moves towards the upstream of the last tooth and the true flow cross area is increased simultaneously

which leads to increase of the leakage.When the total pressure is fixed

the pressure distributed between the teeth decreases linearly along the flow direction and the slope of the curve of the ratio of the pressure between the teeth to the total pressure is related to the total pressure.