关键词: 涡扇发动机, 暖机, 叶尖间隙, 流热固耦合, 过渡态

Abstract:

Aero-engine requires maintaining high rotational speeds for warm-up operations prior to takeoff； otherwise， thrust degradation may occur during the climb-out phase. To address this issue， this study focuses on a core engine of a small-bypass-ratio turbofan and develops a fluid-thermal-solid coupling computational methodology that integrates a 1D fluid domain model with a 2D axisymmetric finite element model of the solid structure. This approach enables coupled simulation across different scales for solid domain analysis， air system evaluation， multi-component thermal analysis， and deformation prediction. Simulation results reveal that tip clearance exceeding design specifications constitutes the primary cause of thrust reduction during takeoff. Warm-up operations effectively reduce tip clearances， resulting in a 0.85% improvement in high-pressure turbine efficiency and a 0.5% enhancement in compressor efficiency. These improvements drive a maximum 0.51% increase in high-pressure rotor speed， augment core mass flow， reduce engine bypass ratio， and ultimately elevate minimum takeoff thrust by 2.4%. Further analysis demonstrates that either extending warm-up duration or increasing warm-up rotational speed can enhance takeoff thrust. However， when the warm-up speed remains below 0.75， increasing rotational speed fails to effectively reduce high-pressure turbine tip clearance. Finally， leveraging sequential quadratic programming optimization， a warm-up parameter optimization model constrained by thrust requirements is established to achieve optimal combinations of minimum warm-up time and rotational speed across various operational conditions.

Key words: turbofan engine, warm-up, tip clearance, fluid-thermal-solid coupling, transient state