Bubbly oil lubrication is a type of lubrication method which has a high potential for application. However, the lubricating performance of the bubbly oil has not been thoroughly considered. This paper aims to investigate the lubricating performance of the bubbly oil including generation of the bubbly oil, viscosity characteristics of the bubbly oil and the application study of the bubbly oil lubrication. Due to space limitation, the work is divided into two parts. Part 1 focuses on the generation method of the bubbly oil, observation of the bubbly oil and the measurement of viscosity characteristics under a high shear rate. Part 2 focuses on the application study of the bubbly oil lubrication in high-speed bearing. A generation method for the bubbly oil was proposed by a combination of the dispersed-air method and the pressurized dissolution one. An experiment setup for generating the bubbly oil, an observation system for the bubbly oil and a specially-designed viscometer for the bubbly oil were developed. The research results show that the generation method for the bubbly oil is of high efficiency and stability and the observation system is operational.
This paper aims to investigate the lubricating performance of the bubbly oil. Due to space limitation, the work is divided into two parts. Part 1 drew a conclusion that the bubbly oil under high shear rate appears a lower viscosity than the non-aerated oil, and the air volume fraction can be adjusted conveniently to reach a high value. Based on this, in Part 2, we intend to explore the feasibility of using the bubbly oil in lubricating high-speed bearings. Here, we select a step thrust bearing as object and analyze its static characteristics under the bubbly oil lubrication. A test rig for the high-speed step thrust bearing was developed to measure the static characteristics of the bearing under the bubbly oil lubrication. The lubrication models for the hydrodynamic step thrust bearing were established to predict the bearing static characteristics. The results show that the static characteristics parameters of the bearing under the bubbly oil lubrication are less than those under the non-aerated oil lubrication, and the differences of static characteristics parameters of the bearing between the non-aerated oil lubrication and the bubbly oil one become larger with the increase of air volume fraction and the external load, especially at a higher speed.
Journal bearing reaction is usually represented by a set of forces and moments concentrated at a single point. This single point support model can not be utilized to describe behavior of fairly long bearing. This technical brief proposes a multiple nodes model for the long bearing considering the distributed characteristics of bearing reaction and the effect of shaft deformation. The static behaviors of a rotor-bearing case with the proposed multiple nodes model are compared with those of the other three typical models. The result shows that the proposed multiple nodes model is practical for the analysis of rotor system with a fairly long bearing, and the distributed effect of bearing reaction should be considered when the ratio of bearing length to the half of rotor length exceeds 0.2.
Oil-lubricated hydrodynamic bearing is a typical support for motorized spindle. However, motorized spindle supported by the oil-lubricated hydrodynamic bearing has disadvantages regarding high temperature rise and low rotational speed. To overcome this problem, this technical brief proposes novel water-lubricated hydrodynamic spiral groove bearings for the motorized spindle. A rotor-bearing static model for the motorized spindle was established considering the external loads and the tilting effect of bearings. An experimental prototype for the motorized spindle was developed, and the theoretical calculation and the experimental research on the bearing static characteristics were carried out. The result shows that the water-lubricated hydrodynamic spiral groove bearings have significant advantages in terms of low temperature rise, good high-speed performance and moderate spindle stiffness, together with the inherent low manufacture cost and high rotation accuracy of the bearings, the proposed bearings can be a potential alternative to the fluid bearing for the high-speed motorized spindle.
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