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Experimental study on a turbine housing with inner insulation structure has been conducted for rapid light-off of the catalyst unit, which is located at the downstream side of turbochargers.The turbine housing with feasible inner-insulation structures has been designed and prototyped. It is referred to as the inner-insulated turbine housing. The concept of inner-insulation structures is a combination of sheet metals and insulators. The turbine housing was built using metal additive manufacturing with powder bed fusion technique.The gas stand test demonstrates the inner-insulated turbine housing under cold start-up with high temperature and idle condition to evaluate the time reduction for activation of the catalyst unit. To acquire the thermal and flow characteristic of the catalyst element, sheathed thermocouples were installed in the catalyst element. As a result, the inner-insulated turbine housing can shorten the activation time for the catalyst element from 18.7sec to 14.6sec compared with conventional one. It has been proven highly effective for rapid catalyst light-off.In addition, turbine performance with thermal energy loss is also discussed through CFD and CHT (Conjugate Heat Transfer) calculations for two kinds of turbochargers, which were examined in the gas stand test. The inner-insulated turbine housing slightly degrades the turbine performance compared with the conventional one. This aerodynamics penalty originates from the modified and simplified geometry of the turbine housing to form feasible inner insulation structures. On the other hand, the inner-insulated turbine housing can reduce the thermal energy loss and contribute to the improvement in aerothermal performance.Eventually, the useful information to attain the high reliability design for an inner-insulated turbine housing has been obtained. |
