A NEW METHODOLOGY TO DETERMINE THE ROTATIONAL SPEED OF A FLOATING RING IN A SHORT RADIAL JOURNAL BEARING

Abstract

Turbocharger rotors for the spark and compression ignition engines are resistant steels manufactured in order to support the high exhaust gas temperatures. The power of these systems is up to 10 kW and the operating speeds are important, ranging between 30000 ÷250000 rpm. The turbocharger lubrication complicates the model, because the classical hydrodynamic theory is difficult to be applied in order to characterize the floating bush bearings operating conditions. Also, the rotational speed of the floating short ring inside the turbocharger is difficult to be determined. The paper proposes a study using Mathcad to find a simplified method for mathematical computation of a floating ring from journal bearing using the equilibrium friction torque acting on the floating ring as result of the two journal bearings: between the shaft and the floating ring and between the floating ring and the housing.