Turbine Housing Boss Design in Turbocharger Application

Turbochargers are widely used to boost internal combustion engines for both on and off high way applications to meet emission and performance requirements. Due to the high operating temperature, turbochargers are subjected to hostile environment. Low vibration level is one of the key requirements while designing turbo for every application. An engine bracket is employed to support turbine housing to reduce total vibration level. Turbine housing in the turbocharger is commonly equipped with boss to accommodate the engine bracket supporting which eventually includes additional constraints in the turbocharger system. Additional constraints in the turbine housing can lead to adverse impact in the Thermo-Mechanical Fatigue (TMF) life of the housing component. Boss generally has critical influence to thermal stress distribution of the turbine housing. Bad design of boss location could bring severe thermal cracking and surface fracture that leads to loss of functionality and serious accident. Hence it is essential to design the boss appropriately in order to avoid housing cracks and loss of functionality. This paper first presents the current design with two bosses that experienced severe cracking problem in the v-band flange location during the engine thermal shock testing, then exhibits sensitivity analysis results for other three new designs with boss changes by means of finite element analysis (FEA). Considering the manufacture cost and the vibration level, new design III with one boss is selected after simulation. The optimized boss design is qualified with same engine thermal shock test. Both simulation and test endured the successful mitigation of cracking risk. This study provides a knowledge base for the design of turbine housing boss and also identifies a strain fatigue life model based on FEA analysis and testing results.