Research On Engine Vibration Isolation And Cooling Module Mounting System

As the engine becomes increasingly compact and powerful, customers gradually have higher expectations for automobile noise vibration and harshness performance than ever before, which attracts the attention of whole industry. This thesis focuses on the vibration of engine and its cooling module and optimizes the mounting system. With the help of numerical simulation, the mounting system of a L6engine was analyzed. The original rubber mounting system was optimized with the objective of modal frequencies and decoupling rates. The amplitude-frequency response under unit excitation of powertrain was analyzed before and after optimization, which indicated the limitations of rubber mounting system. The structure, stiffness and damping characteristics of hydraulic engine mount (HEM) were studied. The five-parameter fractional derivative model was chosen to quantify the dynamic properties of HEMs. The parameters of HEMs were globally optimized with the objectives of powertrain dynamic and mounting force response. This design method was validated by simulation results and offered an innovative solution for HEMs.Experiments were done to identify the factors influencing the vibration of engine cooling module and the stiffness of rubber isolators. The vibration of cooling module and steering wheel were tested with different cooling fans and under various working conditions. Numerical simulation model was built in Matlab to analyze modal frequencies and decoupling rates of engine cooling module, which utilized energy-decoupling theory and helped quantify optimization objectives. The rubber isolators of cooling module were optimized to improve its modal frequencies and decoupling rates in Z and Rx direction, utilizing hybrid genetic algorithm and taking manufacturing and installing constraints into account. The vibration of engine cooling module before and after optimization was analyzed numerically and experimentally, under external excitations and in time and frequency domain. The software platform and design process for mounting system were built to help further design and manufacturing.Combined with experimental and numerical tools, this thesis analyzes the mounting system of engine and its cooling module, which could help mounting design and improve efficiency.