Theoretical Analysis and Optimum Design of High Speed Gas Film Thrust Bearings (Static and Dynamic Characteristic Analysis with Experimental Verifications)

Abstract

This paper describes the theoretical and experimental investigations of static and dynamic characteristics of four types of high-speed gas film thrust bearings, such as stepped, pocketed, spiral and herring bone grooved bearings. The specially designed test rig is used to measure the air film thickness, friction torque, spring and damping coefficients of air film under the high speed operation conditions from 20000 rpm to 40000 rpm. It is verified that the maximum error in the measurements by the present test rig is less than 7 percent. On the other hand, the measured results are compared with the theoretical results for checking the applicability of numerical analysis method to bearing design. Good agreements are seen between the measured results and theoretical predictions, and applicability of theoretical prediction method is confirmed with experimental verifications.

A Review of Grooved Dynamic Gas Bearings

“…Hashimoto and Ochiai [158] tested four sets of thrust gas bearings, i.e., (1) stepped (2) pocketed (3) spiral grooved and (4) herringbone grooved, with the same depth of grooves/steps/pockets. The results suggested that the spiral groove thrust bearing (SGTB) presents the smallest friction torque while maintaining the highest stiffness coefficients for high speed operating conditions.…”

Theoretical Analysis and Optimum Design of High Speed Air Film Thrust Bearings (Application to Optimum Design Problem)

“…On the other hand, the spring coefficient of air film should be increased to improve the dynamic response for the external excitation. In the optimum design, the damping coefficient is neglected as compared with the spring coefficient because the effect of damping coefficient on the dynamic response is much smaller than that of spring coefficient as shown in the previous paper (9) . Figure 1 shows the geometry of spiral and herring bone types of grooved bearings to be treated in this paper.…”

“…The friction torque, Tr, and spring coefficient of air film, k, are obtained by the numerical analysis method developed in the previous paper (9) . The outline of the numerical analysis method is briefly described as follows.…”

“…The specifications and the geometries of the test bearings are shown, respectively, in Table 3 and Fig.9, in which the specifications of conventional designed bearing B has the same specifications as the bearing A except the groove depth hg. Fig.8 Comparison between the optimum designed and non-optimum designed herringbone grooved bearing Figure 10 shows the overview of specially designed test rig for the measurements, which is the same test rig as reported in the previous paper (9) . The test rig consists of a rotor ①, test bearing⑨ and stator⑥.…”

“…In the previous paper (9) , the authors presented the experimental method to measure the static and dynamic characteristics of various types of air film thrust bearings and verified the applicability of the numerical analysis method combining DF method and Newton-Raphson iteration method based on the boundary fitted coordinate, by comparing the calculated results with the measured data for four types of air film thrust bearings. In this subsequent paper, the optimum design methodology to enhance the quality of spiral and herring bone types of grooved bearings based on the numerical analysis method verified in the previous paper is described.…”