Performance Analysis of Hydrodynamic Pressure Finger Seal by Wall Slip Effect

Abstract

Hydrodynamic pressure finger seal1 is a kind of flexible noncontact dynamic sealing device with good application potential. It relies on the ultrathin dynamic pressure film effect produced by the rotation of finger boot and rotor to realize the design of noncontact and low leakage and is suitable for high-speed dynamic sealing parts. However, under the high-speed condition, there is a wall slip effect when the gas flows in the microchannel with a thickness of about 10 μm between the finger boot and rotor, which affects the stability of the dynamic pressure air film and also affects the change of the air film bearing capacity and the leakage rate of the finger seal. Therefore, based on the theory of microflow, the interstitial flow field model of finger seal under fluid dynamic pressure is established, and its slip effect under high speed is analyzed. The results show that the slip ratio of the sealing medium temperature of 500°C and 0.1 MPa conditions reached 27.28%. When considering the slip effect of the wall surface generated by the gas under shear driving, the gas film bearing capacity decreased and the leakage rate increased. When the pressure difference between the upper and lower reaches of the seal is 0.1 MPa, and the rotor line speed is 400 m/s, the gas film bearing capacity decreases by 17.39% after considering the slip effect of the wall surface, and the leakage rate increases by 14.06%. The results provide an important reference for the structural design and leakage control of hydrodynamic finger seal.