Small Diesel Engine Shafting Modal Analysis and Simulation Calculation

The crankshaft is an important component of diesel engine, the vibration caused by engine vibration is an important factor in the performance of its direct impact on the reliability and life of diesel engines. In recent years, with the application of new technologies on the reliability and power of internal combustion engines have become increasingly demanding, the existing vibration analysis of crankshaft systems more and more difficult to fully satisfy the internal combustion engine design. Therefore, Vibration of Crankshaft System on a more accurate, more comprehensive study is very important.In this paper, a small diesel engine crankshaft system for the study, modal analysis theory, respectively crankshaft system in the free state and bound state to conduct a variety of experimental modal analysis. Combined with the results of experimental modal analysis, static and dynamic features of crankshaft system advantages and disadvantages of simulation modeling methods. And the engine running state, the torsional stiffness of the coupling, the load moment of inertia and the piston rod and crank pin lubrication and other contacts at the Department of factors such as the crankshaft torsional vibration were studied. The main work of this paper is as follows: First, the crankshaft of a small diesel engine shaft in the free state and bound state the case for a variety of percussion test mode, and its modal parameter identification. Free state and bound to a variety of situations under the modal test results were compared.Obtained by comparing the mode wheel on the crankshaft greater impact; main bearing and the lubricant film stiffness of the constraints support the bending and longitudinal vibration of the crankshaft a greater impact on the crankshaft torsional vibration was less affected. Therefore, the state can take to free the flywheel, the crankshaft pulley and the piston rod to get the operation modal testing crankshaft torsional mode vibration mode characteristics. Secondly, as a prototype diesel engine crankshaft system in kind, in the three-dimensional modeling software Pro / Engineer to create three-dimensional solid model of crankshaft system; the same time, the crankshaft system solid model into finite element software ANSYS to establish the free state and bound state more kinds of dynamic finite element model simulation, and its computational modal analysis. Modal test results with the comparative analysis of the free state and bound state properties of various dynamic simulation modeling accuracy of the method, advantages, disadvantages and application. Finally, the engine running state, on the coupling torsional stiffness, the load moment of inertia and the contact with the piston rod and crank pin lubrication at factors such as torsional vibration of crankshaft system were studied, torsional vibration frequency obtained With the coupling torsional stiffness, the load moment of inertia and the variation of lubrication. 

Key words: diesel engine; crankshaft system; model analysis; simulation