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Squeeze Film Dampers (SFDs) play a vital role in vibration control an‎d ensuring the dynamic stability of modern turbomachinery, particularly in turbofan engines featuring flexible an‎d high-speed rotors. This research focuses on the complex issue of "reverse design": redesigning the squeeze film damper for the front bearing of the low-pressure shaft of the FJ44 turbofan engine, with the aim of achieving a desired an‎d predetermined damping coefficient by identifying the optimal geometric configuration. To address this problem, an innovative hybrid methodology was developed that integrates the power of analytical modeling with the precision of numerical simulation via the Finite Element Method (FEM). In the first phase, utilizing the theoretical foundations of fluid dynamics an‎d industrial performance criteria, an analytical framework was established to purposefully constrain the infinite design space into a feasible an‎d valid domain. Subsequently, in the second phase, a high-fidelity finite element model was developed using COMSOL software, an‎d a parametric optimization process was systematically executed within this constrained design space to extract the optimal geometric parameters. The optimization results led to a final geometric configuration that achieved the target damping coefficient (150 N.s/m) with extremely high precision (149.99 N.s/m), while simultaneously satisfying all functional constraints, including force transmissibility an‎d pressure concentration coefficients. Furthermore, the study eva‎luated the robustness an‎d reliability of the final design by conducting a comprehensive Uncertainty Quantification (UQ) analysis. Sensitivity analysis revealed that radial clearance an‎d central groove width are the most influential parameters on damper performance, an‎d uncertainty propagation analysis confirmed the high robustness of the design against manufacturing tolerances. Ultimately, this thesis presents a structured an‎d efficient engineering workflow for solving reverse design problems in complex turbomachinery components an‎d introduces a robust an‎d reliable engineering solution—beyond a deterministic design point—by accounting for real-world uncertainties.

دمپر فيلم فشرده , طراحي معكوس , بهينه‌سازي , موتور توربوفن , كمي‌سازي عدم قطعيت

Squeeze Film Damper , Reverse Design , Optimization , Turbofan Engine , Uncertainty Quantification

Mohammadreza Taghian Ghavam Abadi

Dr. Majid Rajabi