Vibration Performance Analysis And Finite Element Model Of6Kw Diesel Generator Sets

The diesel engine is the main excitation source of diesel generator sets, vibrationproduced by it may cause motor fatigue, electrical fault, and shorten the life cycle ofparts. Enterprises and researchers have been facing the problems how to reducedisplacement amplitude of diesel engine and weaken impact on the surroundingenvironment as much as possible. Therefore, it’s important practical significance aboutthe testing and evaluation for the vibration performance of the units. Except this,reasonable optimal simulation for parts of units beyond vibration standards by means ofthe finite element method (FEM) also becomes an essential step.6Kw diesel generator sets are the research object, and working speed of dieselengine is kept at2400r/min in this paper. Compared with national or industry standards,vibration amplitude for each measuring point of the units and isolation effect forsupporting device are tested and evaluated to identify vibration performance defects ofthe units. The data from experiment would be provided for proving the reasonablenessof finite element model. With dynamic FEM, model about diesel generator sets has beenbuilt in ANSYS software.Each module’s own natural frequencies, vibration modes and interconnectednessbetween each other can be observed in the units by modal analysis. After simplifyingthe diesel engine’s internal incentive, displacement amplitude spectrums of observationnodes corresponded to experimentally measured points in X and Z direction areobtained by harmonic response analysis. Through comparing sequence of displacementson measured points from simulation with experiment in the X direction, and sequenceof vibration level differences on damping pad from simulation with experiment in the Zdirection, it is known that FEM of diesel generator sets is reasonable and reliable.Finally, main factors affecting vibration performance of the units have beendetermined, including Young’s modulus and damping coefficient of the rubber material,layout in the bottom of the diesel engine on the damping pad, as well as the thickness ofacoustic enclosures under the actual situation of the units. Within the reasonable rangeof parameters variables, objective optimizations about these factors are done for establishing influence of each parameter variation on the structural vibrationperformance of diesel generator sets by interpolation. The best actual optimizationprograms improving the characteristics have been proposed by means of the aboveprocess.The optimal simulation results indicate that when Young’s modulus and dampingcoefficient of the rubber increase to a certain value in actual allowable rangerespectively, the displacement amplitudes of units are minimized. Except this,increasing the number of damping pads not only reduces the displacement amplitude asmuch as possible, but also helps improving the vibration isolation effect. Effect ofvibration isolation of the units with acoustic enclosures does better than the oneswithout it, but thickness variation has no effect on vibration characteristics of the ones.The methods of finite element modeling and vibration performance optimizationon6Kw small units could be good reference for related diesel generator sets, such as thelarge units.