Title: Effects of turbulence on dynamic performance of accelerated/decelerated hydrodynamic journal bearing system
Authors: Vijay Kumar Dwivedi; Satish Chand; K.N. Pandey
Addresses: Department of Mechanical Engineering, Motilal Nehru National Institute of Technology, Allahabad, U.P., 211004, India ' Vishveshwarya Group of Institutions, G.B. Nagar, U.P., 203207, India ' Department of Mechanical Engineering, Motilal Nehru National Institute of Technology, Allahabad, U.P., 211004, India
Abstract: The hydrodynamic journal bearing system has found the wide spread application in high speed rotating machines such as compressors, gas turbines, steam turbines, etc. The rotors generally operate at high speed; therefore the lubricant flow in the clearance space of journal bearing does not remain laminar for accelerated/decelerated journals. Then, study of the dynamic response of the hydrodynamic journal bearing system considering superlaminar flow is needed. In this paper, the analysis is done for the fluid-flow-field in the clearance space of hydrodynamic journal bearing system using short bearing assumption under laminar, transition and turbulent flow conditions. The positive pressure zone is established after deleting sub-ambient pressure around clearance space. Linear and non-linear motion trajectories at constant speed are obtained using the fourth order Runge-Kutta method. The non-linear motion trajectories during acceleration and deceleration are also obtained. Journal centre trajectories at constant speed and laminar flow, show the expected trend, i.e., system is stable below threshold speed curve, unstable above it, whereas for superlaminar flow, stable behaviour is found at some distance away from the stability curve. The behaviour during stopping/starting of journal centre trajectories is also obtained by non-linear equations of motion. The results also show the expected trend.
Keywords: dynamic performance; hydrodynamic bearings; nonlinear stability; stable region; turbulence; journal bearings; high speed rotating machines; fluid flow.
International Journal of Design Engineering, 2014 Vol.5 No.3, pp.256 - 288
Received: 12 Dec 2012
Accepted: 11 Jan 2014
Published online: 04 Jun 2014 *