Fluid-Structure Coupled Analysis of the Transient Thermal Stress in an Exhaust Manifold

The development of thermal stress in the exhaust manifold of a gasoline engine is considered. The problem is addresses in the frame of a combined approach where fluid and structure are coupled using the GT-POWER and STAR-CCM+ software. First, the external characteristic curve of the engine is compared with a one-dimensional simulation model, then the parameters of the model are modified until the curve matches the available experimental values. GT-POWER is then used to transfer the inlet boundary data under transient conditions to STAR-CCM+ in real-time. The temperature profiles of the inner and outer walls of the exhaust manifold are obtained in this way, together with the thermal stress and thermal deformation of the exhaust manifold itself. Using this information, the original model is improved through the addition of connections. Moreover, the local branch pipes are optimized, leading to significant improvements in terms of thermal stress and thermal deformation of the exhaust manifold (a 7% reduction in the maximum thermal stress).