Thermo-Structural Analysis of Ship Exhaust System

The marine engine exhaust system consists of various elements, such as thermal expansion joints and silencers. It is essential to choose suitable acoustic and thermal insulations, mountings, and vibration dampening devices according to established practices and, if necessary, with the support of numerical analysis. Heat-induced vibrations in the exhaust piping system are a result of the velocity and temperature of the exhaust flow. Expansion joints (Bellows) are used to control these vibrations. This paper introduces a procedure for thermo-structural analysis of exhaust system to predict directional deformation and the developed stresses in the system. Sample case of exhaust inlet and outlet piping with silencer (exhaust piping system) is investigated. The conjugate heat transfer (CHT) analysis methodology is implemented using ANSYS workbench with coupled solution. Thermal solver Fluent and finite element solver ANSYS are used. The results of thermal solution, i.e., the time varying temperature on the piping system due to heated flow of the exhaust gas are mapped onto the structure and used as input load in structural solver to perform structural analysis. In the first case, a constant velocity is applied at the inlet and in another case, a fluctuating velocity pulse is applied at the inlet. The findings indicate that the fluid-thermal-structural model is proficient in accurately anticipating the structural response, particularly vibrations, in relation to variations in the inlet flow conditions. The induced vibrations are purely due to the flow conditions. The maximum axial deformation from two cases of the exhaust system is noted to be 30.47 mm. Based on the predicted results the suitable bellow having vibration absorption capacity e.g., axial compression more than the predicted vibrations can be selected i.e., ~31 mm. The proposed methodology can assist the designers or reviewers to analyse exhaust systems used in ship structures.