Prediction & Analysis Of Rotor Vibration Load

Complex flow environment and various coupling effects have made the rotor load prediction a tough problem to tackle. Prediction of rotor laods is the key issue for rotorcraft design. On one hand, in both the conceptual design and the detail design, accurate prediction of rotor loads can effectively cut down design cycle, save the experimental cost and avoid project rist. On the other hand, by using precise and reliable numerical analysis tools, the study into the laws and physical essence of rotor loads can help the designer find effective ways of improving helicopter performance .Low speed flight,high speed flight and high thrust flight are the typical flight regimes that rotor encounter high vibration loads.These conditions are the key and also difficult part that the engineer concern in the flight envelope.This paper investigates rotor vibration loads in the typical conditions Several works are present as follows:1. Dynamics model of rotor system A comprehensive analysis based on flexible multibody dynamics method is used to model rotor system. Leishman/Beddoes 2D unsteady/dynamic stall model is incorporated and used to calculate rotor blade section airloads. The inflow is evaluated with the free wake analysis.Rotor loads are obtained by trim procedure.2. Prediction and analysis of rotor loads in typical flight regime SA349/2 "gazelle" helicopter is used as the sample in this paper. Rotor loads calculation has been carried out in typical forward flight regime, including transition speed,high speed and steady turn. For steady forward flight, the results correlate well with the test data, and have comparable precision with CAMRADII. For steady turn, analysis captures main characteristics of rotor loads caused by dynamic stall. Several laws of rotor airload and balde vibration load are obtained from both calculations and flight test data.3. Investigation of rotor pitch link load Based on the accurate prediction of sample helicopter's pitch link load in the typical regimes, calculations are extended to other flight conditions. laws and the influence factors of pitch link load are studied by using flight test data and calculation results of sample helicopter and other conventional rotorcraft or rotor models.