Design Of Bearing System Research Articles

A system approach to the dynamic characteristics of hydrostatic bearings used on machine tools

The dynamic performance of the hydrostatic bearing system used on a grinding machine is analysed on the basis of the closed loop control theory. A system block diagram and the corresponding transfer functions are depicted. The response of the system to an impulse impact load is recorded and processed on a digital computer using the curve fitting method. The paper shows that the system approach is a powerful tool for analysis and design of hydrostatic bearing systems used on machine tools.

Steady-State Performance of Squeeze Film Damper Supported Flexible Rotors

The synchronous steady-state operation of a centrally preloaded single mass flexible rotor supported in squeeze film bearing dampers is examined theoretically. Assuming the short bearing approximation and symmetric motions, frequency response curves are presented exhibiting the effect of relevant system parameters on rotor excursion amplitudes and unbalance transmissibilities for both pressurized and unpressurized lubricant supply. Hence, the influence of rotor flexibility, rotor mass distribution, rotor speed, bearing dimensions, lubricant viscosity, support flexibility can be readily determined, allowing for optimal rotor bearing system design. It is shown that with pressurized bearing mounts, the possibility of undesirable operation modes is eliminated and a smooth passage through the first pin-pin critical speed of the rotor is feasible, while absence of pressurization significantly limits the maximum safe unbalance in the vicinity of this critical speed. Significant decrease in transmissibility and rotor excursion amplitudes over those obtainable with rigid mounts are shown to be a practical possibility, with consequent decrease in the vibration level of the rotor mounts and prolongation of rolling element bearing life, while maintaining acceptable rotor vibration amplitudes. A design example is included to illustrate the use of the data.

Application of Gas Bearings to Closed-System Brayton-Cycle Turbomachinery—Recent Accomplishments and Potential Problem Areas

Several development programs to demonstrate application of gas-lubricated bearings to gas turbine machinery are presently under way. This paper presents design and initial test data for a 24,000 rpm, 1300 F (turbine inlet temperature) gas-bearing Brayton-cycle turbocompressor operating in a closed-loop system. The bearing system design for a two-shaft power plant, consisting of a 50,000 rpm, 1490 F turbocompressor and a 12,000 rpm turboalternator, is also described. Test results to date demonstrate that gas lubrication, per se, of gas turbine machinery is definitely feasible. However, considerable data are still needed to prove the practical utility of gas bearings. A brief discussion of the needed investigations is presented.