The Crankshaft Vibration Analysis of Large-type Piston Compressor-Modal Analysis

The crankshaft accidents due to vibration become severe with increasing number of rows of reciprocating compressors.The study on the crankshaft vibration need to be further developed to promote development of the reciprocating compressor.However,the main factor of influencing crankshaft vibration is the mode of crankshaft.In this paper,a modal analysis was done to a crankshaft in a reciprocating compressor and to simplify the crankshaft.The finite element model(FEM) based on Timoshenko beam was built in ANSYS.In the model,the bearing film rigidity was taken into account.This model can also be used to carry out the harmonic analysis and forced vibration analysis on crankshaft.The first 7 modal of the crankshaft was calculated using Lanzos method.The results show that the first modal is torsion mode with natural frequency of 29.073 Hz.The Fourier decomposition was done to the exciting force,which taking the effect of flow fluctuation produced by valve motion during suction and discharge process on exciting force into account.The power spectral density map is obtained to judge whether resonance vibration will happen to the crankshaft under the condition of working.