International Journal of Advanced Engineering Research and Science (IJAERS) Peer-Reviewed Journal ISSN: 2349-6495(P) | 2456-1908(O) Vol-10, Issue-1; Jan, 2023 Journal Home Page Available: https://ijaers.com/ Article DOI: https://dx.doi.org/10.22161/ijaers.101.4 www.ijaers.com Page | 19 Dynamic Characteristics of a Squeeze Film Damper used as Rear Bearing in a Single Spool Aeronautic Gas Turbine Vinicius da Silva Lino 1 , Damásio Sacrini 1 , Adilson Vitor Rodrigues 1 , Geraldo Creci 1* and João Carlos Menezes 2 1 Instituto Federal de Educação, Ciência e Tecnologia de São Paulo (IFSP-BRA), Bragança Paulista - SP, Brasil. 2 Instituto Tecnológico de Aeronáutica (ITA), São José dos Campos, SP, Brasil. * Corresponding author Received: 02 Dec 2022, Receive in revised form: 30 Dec 2022, Accepted: 08 Jan 2023, Available online: 15 Jan 2023 ©2023 The Author(s). Published by AI Publication. This is an open access article under the CC BY license (https://creativecommons.org/licenses/by/4.0/). Keywords— Squeeze Film Damper, Aeronautic Gas Turbine, Bearings, Lubrication, Stiffness, and Damping Coefficients. Abstract— Squeeze film dampers are widely used in aeronautic gas turbines because they effectively absorb vibrations and lessen the stresses on the structural components. In this study, we calculated the stiffness and damping dynamic coefficients of a squeeze film damper with open ends and a circumferential oil-feeding groove. This squeeze film damper was used as a rear bearing in an aeronautic gas turbine designed to generate 5-kN of thrust under ISA conditions. Three different radial clearances were investigated to determine the optimal bearing design configuration for the application because the radial clearance of a squeeze film damper is a crucial element in determining its dynamic stiffness and damping coefficients. To provide superior performance and avoid issues, a rotordynamic analysis using the calculated stiffness and damping dynamic coefficients can be conducted to predict the vibratory behavior of the entire rotating assembly. I. INTRODUCTION Aeronautic gas turbines are internal combustion engines that have an operating power rating ranging from small (100 kW) to large (180 MW). Therefore, they are suitable for electrical power generation or aircraft propulsion. Their primary advantage is their small weight and volume compared with other types of heat engines. Low thermal inertia that allows a full load in a short time is another benefit [1]. The aeronautic gas turbine investigated in this study was a high-performance turbojet designed to generate 5-kN of thrust under ISA conditions [2]. For instance, they can be used in military unmanned aerial vehicle applications. The entire project was developed in partnership with the Department of Aerospace Science and Technology (DCTA), which is a military organization of the Brazilian Air Force Command, and TGM Turbinas Ltda (TGM), with the financial support of the Financier of Studies and Projects (FINEP) and the National Fund for Scientific and Technological Development (FNDCT). The nominal rotation speed of the rotor was 28,150 rpm, although the normal operating range was between 80% and 100% of the nominal speed. It features a single spool system, air intake duct, five-stage axial compressor, direct-flow annular-type combustion chamber, single-stage turbine disk, and exhaust nozzle. Figure 1 shows the aeronautic gas turbine mounted on the test rig. The user-defined specifications were: weight should be approximately 650 N; the length and diameter of the circular section must not exceed 1.5 m and 0.35 m, respectively. The bearings of an aeronautic gas turbine must be carefully designed to provide the required stiffness and dynamic damping characteristics to the rotating assembly to prevent vibration issues. The front bearing of this aeronautic gas turbine is composed of a deep groove ball bearing and a vibration-absorbing element. The dynamic stiffness and damping coefficients of the front bearing were calculated previously [3]. The rear bearing is composed of an specific