Research On The Vibration Characteristics Of Nonlinear Vibration Isolation System Of Diesel Engine

The periodical motion of crankshaft and connecting rod generates vibration sources, causing the vibration of diesel engine, propulsion shafting and hull. As the development of internal combustion engine towards high-speed, light, high-power direction, the vibration of power equipment has becoming the main source of vibration and noises of vessels. The isolator is simplifies as the combination of linear stiffness and damping in the study of vibration isolation system. But with more requirements on the control of vibration and shock in practical application environment, the traditional linear impact vibration isolation theory can no longer meet the requirements. Therefore, understanding the dynamic characteristics of nonlinear vibration isolator is important for estimating the vibration response and improving the vibration isolation effect.Firstly, the paper establishes three-dimensional solid model of a medium-speed diesel engine in Pro/E. Through adding all constraints according to the actual connection relations via ADAMS Software, this paper then builds a linear vibration isolation system with rigid body for diesel engines. Secondly, with the help of ANSYS, by establishing a basis, meshing the model, and importing the mnf file into ADAMS so as to replace the original rigid foundation. Compared with the simulation results of rigid system, the influence of flexible foundation on vibration isolation system is analyzed. Thirdly, after fitting the isolator stiffness curve by high-order polynomial, the function of force and displacement is established. In addition, the nonlinear vibration isolator is obtained by applying spline curve function then the influence of two-layer nonlinear vibration isolation on system response is analyzed. Finally, with further experiment with LMS test system, the impact of liquid vibration absorber is studied.The results show that flexible basis has a great impact on the isolation system. What’s more, lower layer nonlinear isolator plays a decisive role on multi-stage isolation and the inappropriate choice of the combination of parameters of the isolator will, of course, make a poor isolation effect. All of these provide references for the designing of isolation system of actual power plant.