Experimental And Numerical Study On Leakage Characteristics Of Finger Seal

Finger seal is a new type of sealing structure. It consists of multiple annular slices with"fingers"on it, forward and after cover plate and spacer. It is a contact and complaisant seal, which allows the sealing surface radial fluctuating in certain amount. This sealing structure can be used in compressor, turbine and bearing cavity. The leakage of finger seal is at the same level of brush seal, and considerably less than that of labyrinth seal, however, its costs of manufacture is considerably less than brush seal.In this dissertation the main factors that influence leakage of finger seal and the preliminary design principles has been summarized based on the review of literatures. An improved design method of contact pad of the finger seal has been proposed to reduce the sealing clearance. Three kinds of detachable finger seals test models have been made, and the experimental rig and measurement system have been improved.By using these facilities the leakage characteristics of finger seal has been investigated. The results show that the leakage of finger seal is large during its first time usage, while with the increase of the usage time the leakage gradually decrease, and finally tends to be stable. The effects of pressure drop, clearances between fingers and number of finger slice layers on leakage are obvious. While in the experimental range, the rotor speed has negligible effect on leakage.A numerical study of the leakage characteristics of finger seal is also presented in this dissertation. A porous medium model that is adapted from that for brush seal has been used to finger seal. The constants in the model are corrected by using the experimental data. In order to improve the accuracy, one of the constants is replaced by a function of pressure drop. Results show that the leakage scarcely change with the protecting height of front cover plate and the thickness of spacer; the effect of protecting height of back cover plate on leakage is obvious; the leakage of clearance fit is less than that of interference fit.