Dynamic Analysis Of Torsional Vibration System Of Helicopter With Variable Speed

In this paper,the torsional vibration mechanism of variable speed helicopter and its coupling with engine combustion control system are studied.The variable speed helicopter has a single rotor and two engines.The rotor and tail rotor of the variable-speed helicopter are capable of operating indirectly driven by two engines connected to the speed reducer and transmission system.The parts of these mechanical connections constitute a rotor/power/transmission torsional vibration system.When the frequency of excitation force is close to or even consistent with the natural frequency of torsional vibration system,the system will bear too much alternating torque,and the blade will bear a large alternating chord bending moment,resulting in premature fatigue damage of the structure,sometimes it will cause strong vibration on the helicopter.At the same time,the coupling of torsional vibration system and engine combustion control system will cause the problem of dynamic stability.This paper first introduces the dynamic model of rotor/power/transmission torsional vibration system of helicopter with variable speed,establishes the dynamic model of rotor/power/transmission torsional vibration system without damping,obtains its related mass and stiffness matrices,and coupling dynamic model of torsional vibration system and engine combustion control system with damping.Then,the numerical calculation and quantitative processing of the relevant parameters are introduced,and the inherent characteristics of the torsional vibration system are calculated.The natural frequency and intrinsic vibration patterns of each order of the system are obtained,and the resonance of the torsional vibration system is determined.The influence of rotor speed changes on the inherent characteristics is obtained.At the same time,the stability of the system after coupling the torsional vibration system with the engine ignition control system is determined.Finally,the influence of rotor speed on the stability of coupling system and the stability margin of coupling system with different degrees of freedom are analyzed by using Byrd diagram.The influence of relative parameters on the stability of the coupling system is determined by the root trajectory diagram.