Supply Orifice Research Articles

An Experimental Investigation of the Effect of Inter-Orifice Variations on the Performance of an Externally-Pressurized, Orifice-Compensated Air Journal Bearing

The performance of an externally-pressurized, orifice-compensated air journal bearing fitted with various combinations of nonuniform supply orifices of known size is compared with the performance of the same bearing fitted with uniform orifices. In general, it is found that even a substantial amount of scatter in orifice size about a mean, design value does not result in a marked deterioration in bearing performance. Furthermore, the bearing load capacity at a given eccentricity may actually be enhanced (at the expense of a relatively smaller reduction in radial stiffness) by using nonuniform orifices, the best arrangement being one where there is a progressive, circumferential variation of orifice size.

Pneumatic Hammer in a Gas Lubricated Externally Pressurized Annular Thrust Bearing

An experimental study was conducted on the occurrence of pneumatic hammer in a gas lubricated externally pressurized annular thrust bearing. The bearing, which was orifice compensated, was fed by sets of three approximately equal orifices having nominal diameters 0.040, 0.020, 0.015, 0.010, and 0.005 in. Instability was most marked for the supply orifices of nominal diameter 0.020 in. The employment of orifices which had nominal diameters greater or smaller than 0.020 in. tended to make the bearing more stable. Experimental results were compared with the predictions of the simple, lumped parameter analysis.

Experimental Investigation of Whirl in Self-Acting Air-Lubricated Journal Bearings

Bearing characteristics influencing the threshold speed at which large-amplitude self-excited whirl occurs in complete, air-lubricated journal bearings were experimentally investigated. Various combinations of rotors having clearance ratios, Ψ = c/r, ranging from 0.268 × 10−3 to 2.350 × 10−3 and symmetrical bearing assemblies having slenderness ratios, L ′ = L/D, ranging from ¼ to 1 were tested. By varying slenderness and clearance ratios and unit load, by opening or closing supply orifices, or by adding imbalance, the whirl threshold speed could be varied between zero and the limit set by the available power. Experimental methods of identifying the cylindrical and conical modes of synchronous and self-excited whirl are described. The whirl hysteresis region and the nature of whirl at speeds above the threshold are examined. Three methods of avoiding large-amplitude self-excited whirl are discussed.