The finite element model was used to study the lower bearing structure. Considering the above simplified model of the bearing, in the finite element model, the lower bearing structure is regarded as a solid component, and the compressor casing is regarded as a shell component. Under the same bearing distance condition, the ratio of the maximum deformation of the crankshaft to the lower bearing is representative. The natural frequency of the type of bearing type is higher than the natural frequency of the type. We improved the original model used for analysis and performed frequency response analysis on the improved model. The surface velocity of the compressor obtained from the above study was also analyzed by acoustic radiation. The results show that the natural frequency of the first deformation of the crankshaft increases. The journal bearing damping effect also increases. The optimal crankshaft support structure for the compressor installation was studied. The noise test results were optimized and the noise peaks were determined. The band is shifted to the band and the level is reduced, which is consistent with the results of the acoustic radiation analysis. In addition, these not only confirm the determination of the crankshaft vibration that has been described in the noise source section. The conclusion of the rigid mode vibration of the band, and the noise reduction effect has also been observed in the high frequency band. Thus, it can be said that the improvement of the crank support structure is quite effective for compressor noise reduction.
According to the test results, finite element analysis and acoustic analysis of reducing crankshaft vibration, the following conclusions can be drawn: the noise generated by the crankshaft vibration is caused by the same frequency of the first deformation mode of the crankshaft and the acoustic resonance frequency of the exhaust space, and is caused by the vortex The rotary exhaust pressure vibration excitation is caused. It is effective to increase the natural frequency of the crankshaft and increase the bearing damping as a method of reducing the noise caused by the vibration of the crankshaft, and the improved crankshaft support structure contributes to noise reduction in the high frequency band. As a method of increasing the natural frequency of the crankshaft, it is effective to shorten the distance between the bearings. The natural frequency of the bearing is not only related to the rigidity of the upper bearing, but also related to the structural rigidity of the main bearing. If the stiffness and damping of the upper bearing are predetermined, we can predict the natural frequency of the bearing when the bearing structure and bearing type are improved, and predict the sound level value caused by the crankshaft resonance. Based on a series of experimental studies, we have summarized the compressor noise reduction technology, which does not require major changes to the crankshaft structure, but can effectively reduce the noise caused by crankshaft vibration.
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