Study Of The Side Pressure Effect On The Diesel Engine Block Dynamic Characteristics

As the "skeleton" of diesel engine. The block’s dynamic characteristics impact on the operation status, noise and vibration of the machine. The structure of diesel engine is complex, which has numbers of sheet. The complex characteristics are caused by the combined action of three loads, gas pressure, side pressure and bearing load. Side pressure is the dominated exciting vibration source. Side pressure was simplified as a time-dependent load while ignoring the time-varying point of action in the previous studies. Vibration is small with this simplified method. Based on the finite element software. The side pressure was simulated accurately which contained the time-varying point of action.The main content and conclusions of thesis are as follows:1. Calculated the exciting forces including the side pressure and gotten the load boundary of FEA.2. Considering the time-varying characteristic of side pressure, dynamic responses and pre-operational modal analysis about sleeve, main bearing and bolt assembly were calculated in time and frequency domain, based on the finite element software AnsysWorkbench.3. Modal analysis was pre-stress modal analysis which considered the bolt pre-tightening force. Bolt pretension was loaded directly on the bolt solid model. Gotten the first20modal of the components and the single block. The modal mainly concentrated on the skirt of the block. Second cylinder skirt become weak link due to the lack of constraints. And increasing rib there could increase local stiffness. In order to improve local mode of vibration in some frequence, we should increase the local stiffness where has the largest deformation. Optimized some local modal.4. Considering the time-varying characteristic of side pressure in dynamic response and simulating the side pressure more accurately. Getting stress nephogram and the key point of displacement curve and acceleration curve. Explaining the regularity of the curves. Comparing the displacement curves which get in different side pressure loading way and getting the important result that the vibration is stronger when considering the time-varying characteristic of the action point of side pressure.