Open Access Open Access  Restricted Access Subscription or Fee Access

Study on Influence of Different Forms of Damping and Operating Temperature on Whirling Speeds of Rotors

Ravindra Gardas, Bangarubabu Popuri

Abstract


Accurate prediction of rotor whirl speeds is fundamentally important in the design of rotating machinery. There has been an impressive progress in the study of rotor dynamics in the last decade. The use of finite elements for the simulation of rotor system makes it possible to handle complex problems. Rotating shaft tends to bow out at certain speeds and whirl in a complicated manner. This phenomenon results from various causes such as gyroscopic force, internal viscous damping, internal hysteretic damping, external viscous damping and operating temperature. Finite element based dynamic model is developed in Mathcad environment for the prediction of whirling speeds of rotor. The rotor is discretized into finite elements and dynamic equations of motion are developed using Lagrangian method. Different forms of damping viz., internal viscous damping, internal hysteretic damping and external viscous damping are modelled along with operating temperature. These parameters are incorporated into the equations of motion. Expressed the equations of motion in fixed frame or inertial reference frame and rotating or whirl frame of reference. State space method is used to solve the equations of motion and extracting the eigenvalues. Dynamic model is validated with the whirl speed results published in literature for the case studies of individual parameters acting alone viz., undamped rotor, internal viscous damping and internal hysteretic damping. The validated dynamic model is further used in simulation studies of different combinations of internal viscous damping, internal hysteretic damping, external viscous damping and operating temperature acting on the rotor either independently or simultaneously. The prediction of whirl speeds is done with all sixteen combinations of critical parameters. A clear understanding of the influence of different forms of damping and operating temperature on rotor whirls speed helps in optimize the rotor in the design stage and making the robust design for different application, monitoring the rotor vibration and its behavior in the field which can avoid uncontrolled and undesired vibrations results into catastrophic failures.

Cite this Article.
Ravindra Gardas, Bangarubabu Popuri.
Study on Influence of Different Forms of
Damping and Operating Temperature on
Whirling Speeds of Rotors. Trends in
Machine Design. 2017; 4(2): 41–55p.


Full Text: PDF

Refbacks

  • There are currently no refbacks.