Study And Design On The Double-layer Vibration Isolation Of Marine Diesel Engine

As the source of ship power,the diesel engine is accompanied by the vibration of the whole engine in the process of output energy.These vibrations are mainly caused by overturning moment,and finally transferred to the foundation by the support.In engineering,the vibration isolation device is arranged between the diesel engine and the base to reduce the vibration to the foundation.In this paper,based on the single layer vibration isolation of the original 6L16/24 diesel engine,a double layer vibration isolation system is designed according to the engineering design specification.And then,the flexible body model of the double layer vibration isolation system is established by means of the Finite Element Substructure reduction method and the multi-body dynamics numerical method.With the model,the acceleration of each bushing mount at 90% loading points rated speed is calculated.And based on this,the 1/3 octave spectrum in the frequency domain of 10 Hz to 8 kHz band and vibration level as well as the drop of the vibration level of the system are calculated as a new method to predict the vibration isolation effect in engineering design phase.Finally,on the basis of the theoretical analysis of the principle and influence factors of the inertial isolation system,a method for the delight design of the double layer vibration isolation system is proposed.The main research work is as follows:(1)The principle and the characteristics of the isolation(especially double layer isolation)as well as methods of evaluation of the isolation effect in different stages are introduced,analyze the influence of the vibration isolation effect of the system parameters,then explicit the engineering vibration isolation design steps.(2)The experiment of measuring diesel engine vibration signal is designed,and the vibration acceleration of each mounting is measured by the LabVIEW software platform,and analyzed in both the time domain and frequency domain.(3)Using Pro/E,HyperMesh and ANSYS software to establish the finite element model of diesel engine crankshaft and body,and reduce the property file needed for multi-body dynamics calculation.A virtual prototype model for single layer vibration isolation of diesel engine was established in AVL-EXCITE software,simulating the acceleration of each mount point under the condition of rated speed and no load,and comparing them with the experiment data both in time domain and frequency domain,prove the validity of the model built by this method.(4)According to the general design steps and key points as well as the set of vibration isolation target,the diesel engine is designed.The inherent characteristics of the double-layer vibration isolation system are calculated and checked according to the engineering specifications.The flexible body model is established in AVL-EXCITE software,simulating the acceleration of each mounting in the condition of rated speed 90% load,based on this,the 1/3 octave spectrum and the vibration level as well as the vibration level drop calculated,the vibration isolation effect is predicted.(5)Discusses the light design method of the double vibration isolation system according to the principle of the inertia container.The mechanical model of double layer ISD system is established,and the natural and transfer characteristics are calculated by MATLAB simulation,and then the influence of the position and the capacity value on the vibration isolation effect of the double-layer ISD system are analyzed.