Research On The Abnormal Vibration Control Of Main Engine Exhaust Pipes Of A Bohai Ferry

During the operation of the Bohai ferry,the vibration near the bellows in the exhaust pipe of the main engine was strong,which affected the normal operation of the ferry.In this paper,the vibration management of the exhaust pipe is the main content of the research.First of all,a real ship test was conducted to collect the acceleration signals of the abnormal vibration parts of the exhaust pipeline and analyze the vibration frequency characteristics of the pipeline.The main unbalance forces and moments of the diesel engine were analyzed and calculated,and the influence of the diesel engine exhaust pulsation excitation on the pipeline was analyzed at different flow rates.According to the layout drawing of the pipeline system and the actual installation on board,a finite element calculation model of the exhaust pipeline was established,and the modal analysis of the model was carried out using Abaqus software.The thermal modal calculation was completed by considering the influence of gas temperature in the pipeline,and the inherent frequency and vibration pattern of the pipeline system were obtained.The exhaust column frequency was calculated by Comsol software,and the main factors affecting the column frequency were analyzed;the causes of the abnormal vibration of the exhaust pipeline were analyzed by integrating the aforementioned test,excitation source analysis and modal calculation results.Based on the test and calculation analysis,the improvement scheme of adding bellows at the appropriate position of the exhaust pipe was proposed.Modal calculation is carried out on the improved structure to ensure the risk of resonance reduction.The velocity value of vibration test is applied to the pipeline as the excitation for harmonic response calculation,and the change of the response amplitude of the pipeline before and after the improvement is compared and analyzed to judge the vibration reduction effect of the improved structure;and the real ship application was completed according to the analysis results.Finally,the vibration test under the sailing condition of the real ship was carried out,and the results showed that the improvement scheme obviously reduced the vibration response of the main engine exhaust pipe,and the abnormal vibration phenomenon was effectively managed.