A MATHEMATICAL MODEL FOR STUDYING THE REACTION OF AN AIRCRAFT ENGINE BLADE TO A BIRD STRIKE

Аннотация

The method of studying the reaction of an aircraft engine blade to a bird strike is considered. A model of the contact interaction of a soft body with the blade of an aircraft engine has been developed. By comparing the results and mathematical modeling with the results of the experiment, the efficiency and operability of the proposed model and method for studying the bird resistance of aircraft engine blades are proved. Keywords: aircraft engine, blade, bird, impact, stability. them with numerical experiments. In addition to INTRODUCTION reducing cost, the use of a computational experiment can reduce development time by 3 times and improve the quality of the finished product. Therefore, the Cases of birds getting into an aircraft engine raise development of numerical models of contact a number of questions related to the reliability of interaction between a bird (soft body) and an aircraft aircraft equipment and flight safety. The annual cost engine blade (obstacle) with the aim of introducing of bird strikes to commercial aircraft worldwide is them into the practice of designing bird-resistant estimated at US $1.3 billion. Considering that in the blades is an urgent scientific and technical problem. coming years the likelihood of solving the problem of The goal of the work is to develop a mathematical eliminating cases of birds entering an engine during model of the interaction of a soft body with an aircraft operation is very low, one of the effective ways to engine blade and a method for studying its response to reduce the negative impact of birds and improve impact. operational quality and flight safety is to create The process of a soft body colliding with an engines that are resistant to damage resulting from obstacle is a complex physical and mechanical these collisions. In birds, the durability of aircraft process, with its inherent features and certain engines is assessed using mathematical modeling methodological difficulties associated with its methods and experimentally. One of the reasons for modeling. The problem of a collision of a soft body the high cost of developing an aircraft engine is the with an obstacle is a non-stationary, spatial, contact fact that the design process involves the need for problem of continuum mechanics. Figure 1 shows a expensive full-scale testing. One of the effective ways block diagram of the computational and experimental to reduce the cost of engine development is to reduce method for studying the mechanical processes of the number of full-scale tests and partially replace contact of a soft body with an engine blade. 1 Figure 1 - Computational and experimental method for studying the mechanical processes of contact of a soft body with an engine blade In order to verify the numerical model of contact The practical implementation of the method under interaction of the soft body with the blade and consideration involves a consistent transition from a substantiate the reliability of the obtained results, the real phenomenon to an idealized representation. It has results of numerical modeling were compared with the the form of continuous media in order to obtain results of a full-scale experiment. Comparison criteria qualitative and quantitative results from numerical were developed: qualitative and quantitative simulation of a real phenomenon. The physical model comparison using integral indicators and by the describes the phenomenon of water hammer [1], which distribution of physical parameters. accompanies the collision process. There are four stages of water hammer: 1) active (initial), which is PHYSICAL MODEL associated with the propagation of the shock wave; 2) the stage of pressure decline, which is accompanied by The physical model was built with the following the propagation of a rarefaction wave; 3) stage of assumptions in mind: steady flow and 4) termination of the process. A 1) the soft body is a cylinder having a length to mathematical model, represented by a system of diameter ratio of 2; 2) soft body material is considered partial differential equations, describes the mechanical homogeneous; 3) the strength of the soft body is small motion and thermo mechanical state of deformable compared to the strength of the blade, and it is bodies. Together with geometric and physical neglected; 4) given the assumption specified in claim relationships, as well as limit, initial and contact 3, there is no rebound of the soft body; 5) forces of conditions, the equations of the mathematical model viscous damping in the material and friction forces on constitute a general initial-boundary value problem. the contact surface are neglected; 6) flow in the The construction of a numerical model involves material beyond the shock wave front is one- the transition from differential equations (strong form) dimensional, adiabatic and irreversible. to the integral equation of motion (weak form) through Figure 2 shows the four phases of the impact. The the variational principl