EFFECTS OF SUPPORT FLEXIBILITY ON THE TRANSIENT RESPONSE OF ACCELERATED/DECELERATED FLEXIBLE SHAFT

Abstract

The modern high speed rotating machines which operate at speeds above first or higher natural frequencies face vibration problems while accelerating/decelerating through natural frequency zone. In this thesis, the effects of support flexibility on the transient response of accelerated/decelerated flexible shaft has been studied. The dynamic analysis of a simple rotor-bearing system consisting of system natural frequencies and unbalance rotor response during acceleration/deceleration through critical speed zone has been studied considering the variation of bearing film stiffness coefficients with shaft speed and also by assuming the coefficients as constant. The results for the two conditions are compared. A computer programme has been developed based on Finite Element Method to develop the mathematical model of rotor-bearing system. Using numerical methods, first the system natural frequencies are obtained and compared with existing results. Then by using numerical integration techniques the transient rotor response has been obtained for various acceleration/deceleration rates. Also the effects of variation of unbalance mass and numerical integration time step on rotor response has been studied.