Influences of Parameters of Three-Lobe Bearing on the Instability Speed of Rigid and Elastic Rotor Systems

Taking three-lobe bearings supporting rigid and elastic Jeffcott rotor as the research subject respectively,free vibration equation,Reynolds equation and perturbation Reynolds equation of the systems were solved through numerical calculation by use of finite difference method.The influences of bearing(parameters),such as length-to-diameter ratio,minimum clearance(rati)o and average oil temperature on the(instability) speeds of two systems were studied and compared.According the results,decreasing length-to-(diameter) ratio,the instability speed of elastic system increases,but the instability speed of rigid system(fluctuates) in a small region.Increasing the minimum clearance ratio,the instability speed of the two(systems) first decreases and then increases and the influence change of minimum clearance ratio on rigid(system is) more than that on elastic system.Increasing the average oil temperature,the instability speed(of the two) systems increases.