Evaluation of the free-windmilling rotational speed of a damaged wide-chord fan rotor

Jiguo Zhang; Yong Chen; Lu JinXu TangZijian Wang

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Evaluation of the free-windmilling rotational speed of a damaged wide-chord fan rotor

机译：Evaluation of the free-windmilling rotational speed of a damaged wide-chord fan rotor

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摘要

The windmilling imbalance condition occurs after engine shut-down due to fan blade loss, but the engine continues to rotate under aerodynamic forces. This condition can induce undesirable structural excitation throughout the engine and airframe. Especially in the progression of larger high-bypass-ratio fans with fewer blades with larger chords, the excitation is considerably greater and is directly determined by the fan rotational speed. The aim of this study is to explore the windmilling flow through damaged fan rotor numerically according to the zero-torque characteristic, and to develop a prediction method of the windmilling rotational speed of damaged fans. An idealized span-damaged type is introduced to examine the effect of blade-to-blade flow interaction on the rotational speed of fans with various degrees of damage. In full-annulus simulations, whenever the damage of a single blade reaches 35, the positive torque of the damaged blade reaches its maximum value, and the fan rotational speed instead reaches a new minimum. The results also show that the radial flow profiles at the rotor outlet are independent of airflow and can be determined using only the geometry of the damaged fan. This indicates the self-similar nature of the intra-stage flow. According to numerical results, a speed similarity coefficient of damaged fan is identified, and the dynamic pressure at the damaged fan outlet is the appropriate scale for the stagnation pressure loss across the rotor. Further, the engine is regarded as a finite number of variable cross-section frictional ducts, which facilitates the construction of a total stagnation pressure-loss model, allowing the windmilling airflow for any flight Mach number to be obtained. Finally, this study proposes a mathematical model to predict the windmilling rotational speed using the damaged fan speed similarity coefficient and the one-dimensional windmilling airflow function. The model can be applied to the early stages of high-bypass turbofan development and can be used to evaluate the safety characteristics during engine windmilling operations.

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来源
《Aerospace science and technology》 |2023年第9期|108421.1-108421.16|共16页
作者
Jiguo Zhang; Yong Chen; Lu JinXu TangZijian Wang;
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作者单位

School of Mechanical Engineering, Shanghai Jiao long University, Shanghai 200240, China;

School of Mechanical Engineering, Shanghai Jiao long University, Shanghai 200240, China, Engineering Research Centre of Gas Turbine and Civil Aero Engine, Ministry of Education, Shanghai Jiao Tong University, Shanghai, China;

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收录信息美国《科学引文索引》(SCI);美国《工程索引》(EI);
原文格式 PDF
正文语种英语
中图分类航空;
关键词
High-bypass turbofan; Damaged fan; Windmilling speed; Flow similarity;

Evaluation of the free-windmilling rotational speed of a damaged wide-chord fan rotor

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