K. N. Pandey

Effect of the groove dimensions and orientation on the static and dynamic performance of non recessed hybrid journal bearing

The present work is focused on the theoretical study of the performance of journal bearing operating under steady state condition, with particular emphasis on the influence of lubricant supply arrangements. In this paper the influence of the location of the grooves with respect to the load line and influence of groove dimensions on the performance parameter were investigated. The optimum location of the groove axis lies between 600 to 900 to the load line. It is also concluded that smaller groove length yielded lower load carrying capacity.

Analysis of Hybrid (Hydrodynamic/Hydrostatic) Journal Bearing

The Hybrid (hydrodynamic/ hydrostatic) journal bearing system has found wide spread application in high speed rotating machines such as compressors, gas turbines, steam turbines, etc. The present studies include solution of Reynolds equation for hydrodynamic journal bearing with infinitely long approximation (ILA), infinitely short bearing approximation (ISA) and finite journal bearing approximation. Further Finite Journal bearing approximation considers two dimensional solution of Reynolds equation with natural boundary condition, which cannot be solved by analytical method. So, here the solutions for finite journal bearing have been done with finite difference method (a MATLAB® code is prepared for finite difference method) to get bearing performance parameters such as load capacity, Sommerfeld no., etc.

A Model of Fatigue Crack Growth Based on Damage Accumulation

A fatigue crack growth model based on cumulative damage is presented, when a material element ahead of the crack tip, is approached by the tip of the crack. The cyclic plastic zone and process zone ahead of the crack tip are taken as the area where damage accumulation takes place when the material element, first, enters into the cyclic plastic zone and then into the process zone. During this period, the Coffin-Manson damage law in conjunction with Miner’s linear damage accumulation is used to determine the damage in the material element. A constant strain gradient was assumed along the process zone ahead of the crack tip and the size of process zone was taken to be variable and dependent on the range of stress intensity factor. For a cyclic loading, the effective crack driving force takes into consideration the crack tip blunting process. The model results are in good agreement with experimental data available in literature for a number of materials.Copyright

Effects of turbulence on dynamic performance of accelerated/decelerated hydrodynamic journal bearing system

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-low-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.

Selection of Fluid Film Journal Bearing: A Fuzzy Approach

This paper presents a selection procedure for fluid film journal bearing by incorporating fuzzy approach. In this paper a fuzzy based selection model is proposed which can be applied for selection of hydrostatic, hydrodynamic and hybrid journal bearing. Selection criteria is formulated for the choice of space requirement, cost of bearing and load carrying capacity of the corresponding journal bearing. This approach provides a third dimension to the existing method of selection of bearing, which is dynamic and may be further refined to address to every individual needs. Therefore a fuzzy logic approach is used for decision making.