Авіаційно-космічна техніка та технологія (Aug 2021)
Simulation of dynamic impact of an aircraft engine on aircraft wing caused by a fan blade breakaway
Abstract
One of the requirements for a projected aircraft is the ability to continue flying and land in the event of a breakdown of one of the engines. One of the calculated cases of engine breakdown is a fan blade breakaway. This phenomenon causes large vibrations of both the engine itself and the aircraft structure.Design model and method for studying engine vibrations with damage in the form of blade breakaway have been developed; numerical studies of unsteady vibrations of an engine suspended on a pylon have been carried out. Herewith, the following load options are considered: engine operation with fan imbalance before shutdown, which is performed by the pilot; sharp braking and jamming of the fan rotor as a result of breakage of the front elastic support of the rotor, which can occur when the blade breaks off; braking the rotor after turning off the engine.The front bearing of the rotor is ball the bearing installed in elastic elements "squirrel wheel". The ball bearing is modeled as a rigid joint. Outside the elastic element, there are two thin-walled shells, which are intermediate load-bearing elements. With an increase in the imbalance of the fan rotor, the gap in the oil damper closes, the damper housing sits on the shells, switching on their rigidity to work. Thus, the stiffness characteristic of the support is bilinear. The stiffness coefficients of the elastic element "squirrel wheel" and the front support shells are determined by the method of numerical simulation. The fan rotor is modeled as a solid body on bearing supports. The stator of the engine is modeled by a rigid body on an elastic suspension. The pylon and the elastic engine mount elements are modeled by beams of variable cross-section operating simultaneously in tension, torsion and bending.A numerical analysis of the transient vibration processes of the D-436-148FM engine on the pylon of the An-178 airplane is carried out. The most dangerous case of damage as the breakdown of the bearing support after the fan blade breakaway is investigated. The results of the calculations are the graphs of the forces in the bearing arrangements and in the hinges of the engine mounting depended on time.
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