# Study on the Leakage and Inter-Stage Pressure Drop Characteristics of Two-Stage Finger Seal  
[PERSON]  
1 School of Mechanical Engineering, Northwestern Polytechnical University, Xi'an 710072, China; [EMAIL_ADDRESS] (H.Z. ); [EMAIL_ADDRESS] (G.C. )1  
[PERSON]  
1 School of Mechanical Engineering, Northwestern Polytechnical University, Xi'an 710072, China; [EMAIL_ADDRESS] (H.Z. ); [EMAIL_ADDRESS] (G.C. )1  
[PERSON]  
1 School of Mechanical Engineering, Northwestern Polytechnical University, Xi'an 710072, China; [EMAIL_ADDRESS] (H.Z. ); [EMAIL_ADDRESS] (G.C. )1  
[PERSON]  
2 School of Mechanical and Precision Instrument Engineering, Xi'an University of Technology, Xi'an 710048, China; [EMAIL_ADDRESS] (Correspondence: [EMAIL_ADDRESS]; Tel. : +86-136-5920-5298 223  
Compared to the labyrinth seal, the brush seal has lower leakage, longer lifespan, and better sealing stability, and has been proven to be able to replace the labyrinth seal at key sealing locations in aeroengines [4; 5; 6]. When the axial pressure difference is relatively high, the bristle stiffening and blow down effect become more prominent, which increase the contact pressure between bristle and rotor, leading to more severe wear of brush seal, therefore, the sealing performance of brush seal degrades [7; 8; 9]. Finger seal is a new compliant seal, which can adapt to the radial vibration of rotor without damaging the integrity of seal [10]. The measured finger seal leakage is 1/3-1/2 of the traditional labyrinth seal, and the cost of manufacturing is less than 40-50% of the brush seal [5; 11]. Therefore, it has been widely considered by sealing researchers. Later, the sealing workers successively proposed the pressure balanced finger seal and the C/C (carbon/carbon) composite finger seal to further improve the sealing performance of the finger seal based on the traditional finger seal design [12; 13; 14]. Up to now, the theoretical and experimental research on the performance of finger seal has been relatively perfect, and a systematic summary of the research on finger seal has been made by [PERSON] [13] and [PERSON] [15]. Although the finger seal has many advantages over the labyrinth seal and brush seal, the hysteresis and wear of finger seal become more and more serious under the condition of high axial pressure difference, so it cannot meet the requirements of modern aeroengines for advanced seal technology. The pressure balanced finger seal can reduce the hysteresis effect, but the contact force between the low pressure finger element and the rotor increases rapidly with the increase of axial pressure difference due to the non-uniform gas force, so the working life of the pressure balanced finger seal cannot be guaranteed under the condition of high axial pressure difference [16]. The C/C composite finger seal with reasonable design can still ensure the sealing performance and working life under the working condition of high axial pressure difference, however, the high cost manufacture limits the price performance ratio, and the C/C composite finger seal is not suitable for operating at high temperature. With the development of the modern aeroengine, the increased pressure ratio, increased temperature, and increased rotational speed which results in higher vibration levels and possible instabilities put forward more requirements for the seals in aeroengines, as the current seals cannot meet the requirements of aeroengines. So it is still the common goal for sealing researchers to seek new sealing structures that can meet the requirements of long life, low leakage, and low manufacturing cost [17]. In a multi-stage seal, step-by-step pressure dividing function makes the axial pressure difference of each stage seal relatively small. If the finger seal is applied to the design of a multi-stage seal, the excellent sealing performance of the finger seal can be fully exerted due to the smaller hysteresis clearance and the lower contact pressure caused by the smaller axial pressure difference.