Session: 01-01: Aero-engine Operation in Harsh Environments

Submission Number: 176371

Dynamic Response of Turbofan Engine to Shaft Failure: Analysis of Turbine Overspeed Influencing Factors, Fan/Compressor Operating Points and Turbine Overspeed 

Physics-based turbine and turbofan engine models are developed to investigate factors influencing unloaded turbine speed following shaft failure and engine dynamic response under various shaft failure scenarios. Simulation results show that, with all other parameters constant, a higher fuel-air ratio, higher initial speed, higher core mass flow, higher inlet temperature, and lower inlet pressure collectively increase the unloaded turbine’s terminal speed within a given timeframe. Specifically, turbine acceleration is positively correlated with fuel-air ratio, core mass flow, and inlet temperature, but negatively correlated with initial speed and inlet pressure. The influence mechanism of the factors can be categorized into two aspects. On one hand, parameters such as initial speed, core mass flow, and inlet temperature directly affect the calculation of turbine acceleration. On the other hand, such as inlet pressure, core mass flow, and initial speed influence the corrected parameters used in the interpolation process, change the turbine characteristics (e.g., expansion ratio and efficiency), thus indirectly affect the turbine acceleration. However, these parameters inevitably vary and interact concurrently during an actual shaft failure event. Therefore, the mechanisms of fan/compressor operating point dynamic shift and turbine overspeed are also systematically analyzed. Results demonstrate that shaft failure critically compromises the engine’s functional integrity, causing fan and compressor operating points to deviate from steady-state characteristics and inducing the unloaded turbine to accelerate rapidly. Notably, fan-shaft failures produce less severe outcomes than low-pressure shaft failures, while dual-shaft failures are more catastrophic than single-shaft failure. Following shaft failure, the rapid core mass flow reduction causes the fan or compressor operating point to cross the surge boundary. The ensuing surge, involving severe blockage of mass flow, combined with drive loss in the affected component, significantly exacerbates engine performance degradation. Crucially, surge and its associated mass flow reduction and combustor flameout mitigate turbine overspeed by reducing turbine power and average angular acceleration after shaft failure, thereby delaying turbine overspeed and potential disc burst.

Presenting Author: Yuxi Guan Civil Aviation University of China

Presenting Author Biography: A Phd student of Civil Aviation University of China

Authors:

Yuxi Guan Civil Aviation University of China
Shuai Liu Civil Aviation University of China
Jie Bai Civil Aviation University of China