Dynamic characteristics of the multilobe journal bearings with the lobes of different geometry

Multilobe journal bearings are applied in different types of rotating machines such as, e.g. turbounits. The design of such bearings assures proper load capacity, thermal conditions of oil film and stability of the operation of responsible turbounits. However, the design of these bearings can be changed by application of lobes with different geometries. It allows obtaining new family of the dynamic characteristics. The paper presents the multilobe journal bearings with 2- and 3-lobes characterized by different geometry of lobes. The dynamic characteristics in form of the stiffness and damping coefficients of oil film were obtained by perturbation method. Stability ranges of simple symmetric rotor were determined for considered bearings. The iterative solution of Reynolds, energy and viscosity equations allows the obtaining the oil film forces, which were the basis of the bearing dynamic characteristics. Adiabatic, laminar oil film and the static equilibrium position of journal were assumed.