BS ISO 13939:2019 pdf free.Foil bearings – Performance testing of foil journal bearings一Testing of static load capacity, friction coefficient and lifetime.
The test mainly aims to measure and evaluate the static load capacity, friction coefficient and lifetime of foil journal bearings. These primary performance metrics of the foil journal bearing as a mechanical element with a specific dimension are closely related to the performance of the mechanical systems to which the bearings are applied. The configuration of a typical foil journal bearing is shown in Annex A.To compare the static load capacity, the test should be performed after the ambient pressure, temperature and humidity of the environment in which the bearing operates have reached a state of equilibrium. Bearing performance is obtained by measuring the bearing torque and rotational speed of the shaft. In this case, the take-off speed, at which the shaft floats on the top foil without contact, can be observed. For measuring and comparing the bearing performance, the rotational speed shall be higher than the take-off speed.The bearing test facility should be designed to control the relative position of the bearing in relation to the shaft. The bearing housing can be connected to a separate supporter, such as a spring or springs. Otherwise, a vibration-proof facility can be applied to prevent perturbation, which can severely affect the test results. Moreover, excessive friction can cause misalignment of the bearing and thus significantly affect the test results.Figure 1 illustrates the installation of the equipment to measure the bearing torque and static load capacity of the foil journal bearings. Using the measurement system shown in Figure 1, the bearing torque and applied load can be measured and calculated as explained in 6.4. As shown in Figure 2, the displacement sensors are installed at right angles to each other at both ends of the bearing housing. The displacement of the shaft axis is observed by measuring and comparing the obtained values. To measure the rotational speed of the shaft, a fast Fourier transform (FFT) algorithm is applied to the measured displacement data or a rotational speed meter is used. A thermocouple is installed inside the bearing housing to measure the temperature of surrounding air (gas). To measure the surface temperature of a top foil, the thermocouple should be welded to the top foil surface.BS ISO 13939 pdf download.