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This paper deals with the steady-state response of a single disc flexible. rotor supported on two uncentralized squeeze-film damper bearings and sub-; jected to varying degrees of unbalance. The measured responseil-on an experimental rotor operating to speeds exceeding its first bending critical show that the uncentralized squeeze-film damper bearing has a very desira-. • ble effect under the abusive conditions of large unbalance. The unbalan-: ce level was increased by a factor of three in some tests and yet the corresponding vibrational amplitude of the disc, at the first bending critical speed, was increased by less than 30 %. The results predicted : • from a computer simulation study, where the equations of motion are in' .tegrated forward in time until steady-state orbits are reached and automatically plotted, show good qualitative agreement with the experimental. • results. INTRODUCTION The life, reliability and general mechanical integrity of high speed rot-: • or systems can be seriously reduced by the presence of mechanical vibration. One method for reducing the effect of vibration is the inclusion of squeeze-film damper bearing as proposed by Cooper (1). A squeeze-film damper bearing can be simply an annular space surrounding the outer race • of a rolling contact bearing. The fluid within the clearance annulus is • the oil employed in lubricating the rolling contact bearing. The outer race cf the rolling contact bearing is not allowed to rotate within the clearance circle but it can move with fixed coordinates (orbit) within this space. It is this movement which produces the squeeze-film from which tht:device gets its name. Two main types of squeeze-film damper bearing exist. One type allows the • bearing to settle freely to the bottom of the clearance circle until unbalance causes it to lift-off. The other type has the bearing outer race sup-• ported by a set of cantilever springs (known collectively as a squirrel• cage) so that the bearing is held centrally within the clearance space. The tat design variants are shown schematically in Fig. 1. The first of : the, types, which is often refered to as an uncentralized squeeze-filin * Lecturer, Aeronautical Department, Military Technical College, Cairo, EGYPT. ** Head of Applied Mechanics Group, School of Mechanical Engineering, Cranfield Institute of Technology, Bedford, ENGLAND. L+ The Experimental work was carried out in Cranfield Institute of Tech---i noluyy , ENGLAND. CANTILEVER CENTRALIZING SPRING (SQUIRRELCAGE I

THE UNBALANCE RESPONSE OF A FLEXIBLE ROTOR MOUNTED ON UNCENTRALIZED SQUEEZE-FILM DAMPER BEARINGS