Fault Diagnosis of Gas Engine Bellows

Abstract

A bellow of an waste gas exhaust system has cracks after working 80 hours. Modal test and force source analysis were carried out for the system. It was found that cracks of the bellow was caused by resonance. The system dynamics model is established by using finite element software. The exciting force is introduced into the model. The load on bellows exceeds the maximum permissible stress. The bellow will have cracks in this state. The resonance region is avoided by modifying the structure. After structural adjustment, the bellow did not break again. Introduction The steel bellows has good ductility, high tensile strength, light weight, good durability and fast construction speed. It is widely used in engineering [1] . The performance and reliability of steel bellows is highly dependent on the design. Hamada [2] provided theoretical design formulas and standards for bellows designers. In connection with the unreinforced U-shaped titanium bellows, Qin [3] deduced the fatigue life design formula accordingly and analyzed its fatigue fracture form. Ghader Faraji [4] described the relevant finite element parameter extraction in the process of manufacturing metal bellows. He gave specific description of the relevant parameters. Tu [5] found that the bellows expansion process is equivalent to the secondary processing of itself. There are residual stresses on the inner and outer surfaces of the approximate round tube after forming. Mehrabadi [6] found that the stress of the bellows after expansion focus on the inner side of the original wave peak. The outer side of the trough and the stress value is related to the cross-section shape of the bellows. The more the number of flaps, the denser the residual stress distribution. Fault Situation and Analysis Fault Situation During the test of the bellows of a gas turbine waste bypass system, two fractures were reported. The first was found after 320 hours of durability. The second was discovered after 80 hours of replacement.