Effect of Clearance and L/D Ratio on Rotor Dynamic Stability of Journal Bearing Assembly

Abstract

Rotor dynamic performance for journal bearing is analyzed using finite element approach. Calculations are carried out to find the stiffness and damping coefficients for the considered clearance value and L/D ratio. Standard bearing formulae based on Somerfield number is applied to find the dynamic coefficients. Finite element analysis based on spring and beam elements is used to find the whirling speed for different speeds of the rotor. Here elastic support condition is considered due to the change of stiffness of the bearing for the given applied speed. The results shows higher L/D ratio has better vibrational characters compared to the lesser L/D ratio bearing assembly. But higher clearance is reducing the fundamental frequency of the system which is not desirable for better dynamic stability.