Journal of Applied Mechanical Engineering

Helicopter main rotor vibration analysis with varying rotating speed

2^nd International Conference on Fluid Dynamics & Aerodynamics

October 19-20, 2017 | Rome, Italy

Salvador Castillo Rivera

City University of London, UK

Posters & Accepted Abstracts: J Appl Mech Eng

Abstract:

In this work, different modelling aspects of helicopter dynamics are discussed. The helicopter model has Sikorsky configuration, i.e., main rotor in perpendicular combination with a tail rotor. The rotors are articulated and their blades are rigid. The implementation of the main rotor has been carried out considering the flap, the lag and the feather degrees of freedom for each of the equispaced blades as well as their dynamic coupling. The model has been set up by using VehicleSim, software specialized in modelling mechanical systems composed by rigid bodies. The vibrations are studied as they have a great interest in the helicopter due to the rotating behaviour of their rotors. In fact, the main cause of vibration in the fuselage comes from the main rotor. The variation of the main rotor speed generates vibrations on the helicopter and they are analyzed on the fuselage by using short time Fourier transform processing, which allows to study the spectrums of vibrations. So, a model in which the main rotor angular speed is not constant and changes by means of a PD controller is presented. This allows to obtain different combinations of frequencies between the main rotor standard frequency and external varying frequencies, this combination of frequencies is important to study and analyse the vibrations appearing in the fuselage as a consequence of these perturbations. Various tests in absence of external perturbations are carried out to study pure vibrations on the fuselage roll and pitch axes under the action of this varying rotating speed. Spectrograms analysis on the fuselage roll and pitch axes reflected appearing vibrations because of the varying nature of the main rotor angular speed.