Development and modal analysis of a discrete model of a wing with engine

Abstract

The object of this study is the vibrations of a wing with an engine. This study aims to develop a model with the smallest possible number of degrees of freedom (DOF) for solving the influence of imbalance and engine axis tilt on aeroelastic oscillations of the wing console. Current economic constraints and environmental regulations require the development of more efficient aircraft configurations. The observed trend in aircraft design to reduce aerodynamic drag and fuel consumption and emissions is to increase the wing aspect ratio. However, under the same operating conditions, a thin wing is more flexible and subject to higher deflections. This effect can lead to changes in the dynamic behavior and aeroelastic response, potentially leading to instability. Following the requirements of AC 25.629-1B, the absence of aeroelastic instability must be demonstrated for all speed and altitude combinations. In this case, all possible engine operating conditions and combinations of conditions must be considered to consider the influence of gyroscopic loads and thrust on aeroelastic stability. A review of publications showed that models with a maximum of three DOF are used to study the aeroelasticity of a high aspect ratio powered wing. A discrete wing model with an engine has been developed. This model has 23 DOF. This model significantly expands the capabilities of the numerical analysis of aeroelastic oscillations compared with the generally accepted model with three DOF, which reduces wing oscillations to oscillations of an average profile. This number of DOF is sufficient to approximate the shapes of the wing’s bending and torsional oscillations in the frequency range up to the engine speed. A rotating imbalance force can be applied to the concentrated mass, which models the engine at the pylon end. The effect of imbalance in any given plane on the dynamics of the model can be investigated to meet the requirements of AC 25.629-1B. Modal analysis of the discrete model was performed. The obtained frequencies and modes of oscillations were similar to those of the high aspect ratio wing of a transport aircraft. In the future, this model will be used to investigate the effect of engine imbalance and tilt on aeroelastic oscillations, flutter, and the transition to limit wing oscillation cycles.