Abstract
Blade off that occurs during operation will generate a sudden imbalance excitation and make the rotor become inertially asymmetric, which leads to large instantaneous impact load and induces more complex rotor dynamic phenomena. In order to study the transient dynamic characteristics for complex rotors suffering from blade off, a mathematical model for solving the response of the gas generator rotor in the aero-turboshaft engine is established based on the FE method and DOF condensation, in which the complex structural characteristics, transient impact load, and inertia asymmetry of the rotor are considered. The complex impeller structure is modeled by piecewise linear fitting with cylindrical beam elements and tapered beam elements. Without loss of generality, the modeling method suitable for complex rotors is verified through a general complex test rotor with modal experiments. Based on this, the responses are solved for carrying out parametric studies and an understanding of the transient dynamic characteristics of the rotor under the extreme working conditions of blade off. The results show that the blade off has a great impact effect on the time-domain waveform, frequency components, and rotor orbits. At the instantaneous stage after blade off, the complex motion is composed of synchronous motion and some lower-order natural modes excited by blade off. Although the transient responses with blade off at different rotational speeds have similar time-varying characteristics, the impact factor is sensitive to the rotating speed. Most important is that the parameter of the blade off location will not only have a significant effect on the impact factor, but also on the frequency spectrum. These dynamic characteristics as well as impact effect provide certain guidance for the fault recognition and dynamic analysis to these complex rotors suffering blade off.
Highlights
Blade off is a typical extreme load condition [1] that an aero-engine may suffer, which may lead to severe vibration of the aircraft and even cause the failure of some parts of the aero-engine
In order to better understand the fault features of complex aero-engines when blade loss occurs during operation, this paper aims at establishing a more reasonable dynamic model to study the dynamic response of the complicated rotor suffering blade off
It can be seen that when the sudden unbalance is applied on the rotor, i.e., the blade off occurs at the moment t = 0.05 s, the amplitude of the transient response increases suddenly and quickly reaches a peak point, oscillates downward within a certain time range, and decays to a stable value after several revolutions due to the damping existing in the system
Summary
Blade off is a typical extreme load condition [1] that an aero-engine may suffer, which may lead to severe vibration of the aircraft and even cause the failure of some parts of the aero-engine. For the gas generator rotor used in the turboshaft engine, there is very little research on its dynamic modeling and response analysis This is no doubt because the previous dynamic models based on constant-section beam elements or ANSYS solid elements are difficult for characterizing variable-section rotors with complex profiles, the calculation cost is very large, and the conclusions or laws obtained provide limited guidance to the actual engineering. In order to better understand the fault features of complex aero-engines when blade loss occurs during operation, this paper aims at establishing a more reasonable dynamic model to study the dynamic response of the complicated rotor suffering blade off. Taking the typical gas generator rotor in an aero turboshaft engine (ATE) as the research object, a more reasonable rotor dynamical model is proposed based on the FE method and DOF condensation theory. The work can provide better theoretical and technical support for rotor modeling and fault identification of aviation turboshaft engines suffering from the blade off event
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