Translated Abstract
Due to the advantages of low production costs, low power consumption and good stability, the floating ring bearings are widely used in the high speed and light load rotating machinery such as turbocharger and internal combustion engine. However, at present there are still many problems with the design and use of the process. For example，dropping down of the ring speed ratio，sticking of the bearing with the shaft，even catastrophic failure at high speed. Aiming at to solve these problems, this study attempts to use the surface texture to improve the lubrication performance of floating ring bearing and bearing system under harsh working conditions. Surface texture as a means for enhancing tribological properties has been proven to be very efficient in reducing the friction coefficient and the wear rate of mating surfaces. It can be seen that the surface texturing is one of the important means of technology in the future decrease the friction. It is of great significance to try to introduce the concept of surface texture to improve the lubrication performance of the floating ring bearing under harsh operating conditions. The main contents of this thesis are summarized as follows:
The theoretical predictions of the lubrication characteristics of floating ring bearing shows significant discrepancies with test data at high speed condition. Aiming at solving this problem, the model considering the influence of thermal effect is established to investigate the lubrication performance of floating ring bearing. Comparing the test result and simulation result, rationality and feasibility of the thermal model is verified. The results show that the calculated speed ratio can be in accord with the experimental value. The influence of external factors on the speed ratio is also addressed. Furthermore, at different rotating speeds the structure parameters of inner and outer film oil clearance，thickness and width of ring on lubrication characteristics of floating ring bearing were studied. The results could provide an important reference for find out the influence mechanism of the structural parameters of bearing on lubrication characteristics of floating ring bearing and reference for design and analysis of floating ring bearing lubrication characteristics.
To study the effects of the surface texture on the performance of floating ring bearings (FRB), a thermal model is employed to estimate the FRB performance. The model is first validated through comparing the predicted results with measured data. Then, the effects of three types of textures on the bearing behaviors are systematically studied. The results show that textures can considerately affect the FRB performance, such as significantly increasing the side leakage and reducing the temperature rise, which is desirable in many cases for the turbocharger development.
The continued interest in the use of floating-ring bearings for the control of oil film whirl in rotor bearing system is attested by the numerous publications devoted to this bearing. However for the commercial reason much of the reported experimental work either reveal the bearing parameters nor the bearing performance at these tests has been reported in the open literature. Hence, an experimental program was undertaken on the condition that the shaft speed ranges between 1000 ~10000 r／min, the bearing load 30~100N respectively to determine the effects of surface texture on ring speed ratio. The non textured specimen experimental results show that Floating ring bearing can effectively reduce the relative speed between the journal and the bearing, on the heavy static load condition, the ring speed ratios rapidly decreasing as the shaft speed increases, on the light static load condition, the ring speed ratios rising as the shaft speed increases, and there are nonlinear relationship between ring speed ratio and shaft speed. The textured specimen results show that on the heavy static load condition, the ring speed ratios increasing as the shaft speed increases. This means surface texture has an attractive potential application in improving the performance of floating ring bearings.
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