dual-rotor system

dual-rotor system

A system of helicopter rotors in which there are two counter-rotating rotors driven by coaxial drive shafts.
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In order to investigate the dynamic characteristics of pedestal looseness, a dual-rotor system dynamic model is established based on dual-rotor system test rig and one-dimensional finite element model of the dual-rotor system, in which loosened pedestal is considered a rigid body doing plane motion and pedestal's collision with foundation and bolts is also considered.
Figures 1(a) and 1(b) show the dual-rotor system test rig and structure diagram, respectively.
One-dimensional finite element model of dual-rotor system (excluding pedestal) is built based on Timoshenko beam element, as presented in Figure 2, which is composed of the inner rotor (node 1 to node 13) and the outer rotor (node 14 to node 20).
As for the dual-rotor system test rig in the research, the fastening bolts on one side of the pedestal are loosened to simulate the pedestal looseness.
Based on dynamic equations of dual-rotor system, systematic transient dynamic simulation is accomplished.
The time waveform of outer rotor and inner rotor with pedestal looseness fault is shown in Figure 8(a); the axis orbits of dual-rotor system with and without looseness fault are illustrated in Figure 8(b); the frequency spectrum plots under normal status and fault status are illustrated in Figure 9.
The time waveform of outer rotor and inner rotor with pedestal looseness fault is shown in Figure 10(a); the axis orbits of dual-rotor system with and without looseness fault are illustrated in Figure 10(b); the frequency spectrum plots under normal status and fault status are illustrated in Figure 11.
In order to verify the efficiency of the theoretical model, the unilateral looseness fault of inner rotor's bearing pedestal is simulated in the dual-rotor system test rig.
In the study, the dynamic model of dual-rotor system has been proposed to describe the mechanics of pedestal looseness between the pedestal and the foundation and bolt cap.
1) A new dynamic model of dual-rotor system with pedestal looseness considering the effects of the collision is presented.
Caption: Figure 1: Dual-rotor system test rig and structure diagram.
Caption: Figure 2: The node map of one-dimensional finite element model of dual-rotor system.
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