Parameters Sensitivity Study on Dynamic Characteristics of Turbofan Engine Mounting System

The hinged multi-link system is often used as the mounting system of aircraft turbofan engines. It is mainly composed by multiple ball joints and links. As an important connecting structure, the dynamic performance of the mounting system directly affects the vibration transmission from engine to the cabin. In order to reduce the transmission of vibration and noise to the cabin, it is necessary to conduct parameters sensitivity study on vibration transmissibility of the mounting system, and further guide the parameter design for the mounting system. In this article, a hinged multi-link mounting system which used in a turbofan engine was selected as the research object. Then the multi-body dynamics method was used to model the mounting system, and the Hertz contact model and the Coulomb model were used to model the ball joints. Seven parameters including the ball joints parameters and the angle of the links were selected as variable factors. The influence of variable factors on the system vibration transmissibility within the engine operating frequency range was studied. The results show that, the stiffness of the main ball joint and the after ball joints have linear effect on the vibration transmissibility, and the other parameters have nonlinear effect on the vibration transmissibility. In addition, the second-order effect of the side links angle and the first-order effect of the main ball joint stiffness are the main influencing factors, so they can be used as the main design parameters. The center link angle and the after ball joints stiffness are the secondary influencing factors, which can be used as the secondary design parameters. The other parameters of the ball joints are low sensitivity factors, which can be ignored in the design. The innovation points lie in: (1) The main sensitive parameters for the vibration transmissibility of the turbofan engine mounting system were proposed in this study. (2) The nonlinear impact and friction of the ball joints in the mounting system were considered. (3) By using the self power spectrum algorithm, the total vibration transmission characteristics of the mounting system over a wide frequency range was obtained. It is beneficial for improving system robustness. The research results of this article can provide guidance for the parameters design of the turbofan engine mounting system.