Effect of the sleeve profile on the stability of rotor operating in multilobe journal bearings

Multilobe journal bearings with the sleeve of the 2-, 3 or 4- sliding lobes of cylindrical profile are applied in different types of rotating machinery. The design of such journal bearings, the number of lobes and oil grooves improves thermal state of bearing at higher speeds and the stability of operation. The paper describes the results of the calculations of dynamic characteristics and determination of stability ranges of simple symmetric rotor operating in the offset types of multilobe journal bearings. The dynamic characteristics of supporting bearings are defined by four stiffness and damping coefficients of oil film. The iterative solution of Reynolds, energy and viscosity equations allows the obtaining of the load capacity of bearings and the required dynamic coefficients of oil film. Adiabatic, laminar oil film and the static equilibrium position of journal were assumed. The oil film pressure, temperature, viscosity fields and the oil film forces were the basis of the bearing dynamic characteristics and stability determination