Design and Evaluation of Silicon Nitride Turbocharger Rotors

Abstract

Two types of silicon nitride ceramic rotor have been introduced into the Japanese market by Toyota Motor Corporation, named CT26 and CT12A, to improve engine acceleration response by the reduction in moment of inertia. In order to design a suitable blade shape for a ceramic rotor, the critical stress of the blade was determined by the results obtained experimentally from correlating the fracture origin over spintested rotors with centrifugal stress at fracture. A suitable blade shape has been determined for the CT26 turbocharger rotor type, which is identical to the metal rotor except for the disk diameter of hub back face and the blade thickness. The CT12A type is of similar design to the CT26 type; all dimensions could be reduced except for the inlet blade thickness, which is determined by foreign object damage (FOD) resistance.