공기 포일 베어링으로 지지되는 2 리터급 디젤 차량용 터보차저의 회전체 진동 안정성 및 과급 성능에 관한 연구

This paper presents the rotordynamic stability and performance measurement of oil-free turbocharger supported on gas foil bearings for 2 liter class diesel vehicles. Oil-free turbocharger was designed and developed via the rotordynamic analyses using dynamic force coefficients from gas foil bearing analyses. The rotordynamics and performance of the oil-free turbocharger was measured up to 85 krpm while being driven by a diesel vehicle engine, and compared to a commercial oillubricated turbocharger supported on floating ring bearings. The test results showed that the gas foil bearings increased the rotor speed by ~ 20% at engine speeds of 1,500 rpm and 1,750 rpm, yielding the reduction of turbine input energy by more than 400 W. Incidentally, an external shock test on the oil-free turbocharger casing was conducted at the rotor speed of 60 krpm, and showed a good capability of vibration damping due to the well-known dry friction mechanism of the gas foil bearings.