An Experimental Study of the Steady-State Response of Oil-Film Dampers

Oil-film dampers are an integral feature of most high-speed, lightweight turbo engines, in which they are used to suppress undesirable shaft dynamic responses. They are generally located at the antifriction main bearings. An experimental study of the steady-state response of an oil-film damper at a main bearing was conducted on the high-speed rig developed for this purpose. The rig and some typical test results on a damper with a discreet number of oil-inlet ports were described in an earlier publication [1]. In this paper, the experimental results are presented on dampers with different geometries and oil-supply arrangements. The results are presented in terms of transmissibility, deflection and damping coefficient plots. The response of the damper with radial springs to simulate gravity effects in a vertical rotor arrangement is compared to that without radial springs. It is shown that there is a range of speeds up to which the response of the damper is synchronous and beyond which it becomes nonsynchronous. No nonsynchronous behavior was observed for damper amplitudes not exceeding the mass eccentricity of the rotor, that is, the displacement of the rotor center of gravity from the geometric center for a given unbalance. It appears that in a good damper design the maximum amplitude does not exceed the mass eccentricity of the rotor.