Modal Analysis And Damper Design Of A5Cylinder Diesel Engine With Elastic Constraints

Now, diesel engine is still the power producer of shipping and automobile, etc. As a reciprocating power machinery, diesel engine is born with vibration problems, due to the unbalanced forces and moments, and this perplexes people all the time. During the practical engineering applications, diesel engine with5cylinders vibrates particularly seriously. On the bench tests and sea trials, a certain two-stroke marine diesel engine with5cylinders vibrates badly in transverse direction. Therefore, modal analysis of this diesel engine is conducted by FEM, and a transverse damper is designed in this paper.Firstly, Pro/E is used to create the simplified3D solid model in this paper based on a5cylinder diesel engine, and Ansys12.0is used to conduct modal analysis with elastic constraints on the base, and then the first20modal shapes and natural frequencies of this diesel engine are obtained. After analysis, the third order of X-type transverse vibration is maybe the reason for resonance in the speed range of this diesel engine. By contrast with the results of vibration bench test, the effectiveness of the results of modal analysis is further demonstrated.Secondly, a passive dynamic damper for the X-type transverse vibration is designed in this paper. Ansys12.0is used to conduct modal analysis to determine damper’s inertia mass in this paper, and then the spring’s stiffness and silicone oil’s damping coefficient are determined, and ultimately the damper’s structure is designed in brief.This study shows that FEM modal analysis can obtain the modal parameters of the diesel engine, as well as determine the inertial mass of damper effectively, and provide reliably theoretical basis for vibration analysis and transverse damper design.