Thermal Mechanical Fatigue and Creep Interaction in Turbine Housing Divider Wall Design

Turbochargers are commonly used to boost internal combustion engines for both on and off high way applications to meet current emission regulations and performance requirements. Divider wall turbochargers have two exhaust gas inlets and twin scrolls with the divider cast wall connected. Turbochargers with divider wall feature could conserve an engine’s exhaust pulse kinetic energy for great turbine wheel efficiency. It is widely used in 6-cylinder engine applications. Turbochargers with divider wall configuration operate in very hostile conditions with high temperature and great thermal gradient. Using thinner divider wall feature benefits aerodynamic performance, but with the configuration turbine housing may show cracks and large deformation during thermal cycling. In order to achieve the balance between mechanic and aerodynamic, design study of a reasonable divider wall is required. This paper first presents the initial design with thinner divider wall, which experienced severe cracking problem in the divider wall location during the engine thermal shock testing. In order to capture the failure mode at divider wall region, finite element analysis (FEA) with thermal mechanical fatigue (TMF) and creep interaction is performed. The simulation repeats the failure mode very well which shows this numerical analysis method is convincing and fast for further study. Base on the failure case and successful cases, TMF with creep interaction simulation criteria is proposed. The criteria could be used as the reference for the further design, and the design should be controlled within the criteria limit. Based on the methodology and the criteria, the new design is analyzed and the simulation result shows the risk is low. Engine thermal shock testing is done for the final validation. This design has acceptable cracks and no large deformation at divider wall location under the testing condition. TMF and creep interaction gives a right and fast methodology to capture the failure mode at divider wall. Meanwhile it provides a knowledge base for the turbine housing divider wall design.