Simulation Modelling of the Process of Birds Fly into the Turbojet Aircraft Engine Fan to Determine Most Dangerous Cases in Terms of Blade Strength

Abstract

The paper considers an approach to numerical simulation of bird strike on the fan blades of an aircraft dual-flow turbojet engine. The purpose of such simulation modelling is determining the most critical cases of bird impact from the strength viewpoint of the blade apparatus. These cases are determined by the Airworthiness Standards for aircraft engines, which must be met for all of their designed components. However, only some of them are the most critical and subject to in-depth verification. To identify such cases, finite-element modelling using explicit dynamics methods is applied. The choice of the most critical case from the strength viewpoint of the blades is made between two variants simulating a flock of medium-size birds or a single big bird with given sets of parameters (mass, sizes, speed, angle) with the rotating fan wheel. The model of the fan impeller is used as a circular assembly of the sector of fan blades on a model disk with a hydrodynamic model of a single big bird or a flock of medium-size birds with discretization by the SPH method. A feature of the proposed approach is an algorithmic solution for damping parasitic oscillations of the blades that occur during the instantaneous application of the angular speed. The distributions of the main parameters of the stress-strain state of the blades depending on time are obtained. This data is an informative simulation of process dynamics. They allow assessing the possibility of failure of the material of the blades and the overall bird resistance of the structure. These virtual experiments make it possible to conclusively narrow the number of tested parameter sets for a given design class in compliance with the Airworthiness Standards. The proposed computational models and algorithmic schemes for carrying out numerical analyses are verified according to the data of bench experiments. The use of such computational analysis tools makes it possible at the design stage to reduce the time and resources spent by reducing the number of bench experiments required for certification.