In aerostatic thrust bearings (ATBs), a high-pressure gas film with a certain bearing capacity and stiffness is formed by passing high-pressure gas between the moving surface and the static surface. Aerostatic bearings have outstanding advantages in the following aspects: high precision, high speed, and long service life, etc. They are widely used in many fields, such as high-speed air spindles, precision machine tools, air-bearing guideways, turbine machinery, and high-speed drills. With the pursuit of higher efficiency and high-precision machining machinery, there is an increasing demand for high-performance ATBs. Much effort has been spent on the study of ATBs, such as improvements in load capacity and stiffness, and the enhancement of stability. Some significant progress has been achieved. In this paper, the research developments of ATBs are summarized from several aspects, such as theoretical models and experimental methods, static performance, dynamic performance, and applications. In addition, insights on the breakthrough and development trends of ATBs are put forward. It is hoped that this paper can provide some guidance for the design and application of ATBs.

In high-speed motors, there is a huge amount of heat generation from core and winding losses, which may result in thermal failures or motor performance deterioration. In the prevention of heat accumulation, efficient cooling technology is critical for smooth and reliable motor movement. This paper summarizes the diverse application of high-speed motor and thermal requirements, such as in electrical devices, turbo-machinery, and high-precision machine tools. Three paths of case convection—cooling, internal ventilation cooling and spindle core cooling—are analyzed. Methods for configuring thermal resistance and improving cooling efficiency are summarized. Among them, coolant flow characteristics and flow channel shapes, gas supply ventilation systems, and methods to reduce air resistance, as well as axial cooling and integrated heat pipe structures, are extensively investigated. Finally, the development prospects of high-speed motor cooling are also forecasted. At present, the primary research directions are to reduce the heat generated by the heat source, utilize the latent heat of the coolant, optimize the cooling flow path of the shell, design an axial air-cooling circulation system, and enhance the heat dissipation of the spindle.

The liquefaction of hydrogen is considered to be a crucial process in the large-scale utilization of hydrogen energy. In hydrogen liquefaction, hydrogen turbo-expander is a key refrigerating machine for high liquefaction efficiency. Performance of the turbo-expander is directly affected by the hydrogen gas bearings. To obtain a deep understanding of the performance characteristics of hydrogen gas bearings, the static and dynamic characteristics of herringbone grooved journal bearings under hydrogen and other lubricating gases were numerically calculated and compared. The bearing load capacity and critical mass of hydrogen gas bearings were slightly lower than those of helium-, air- and nitrogen-lubricated bearings. To improve the performance of the hydrogen gas bearings used in high-speed turbo-machinery, the influence of working conditions was analyzed. It is found that the load capacity of hydrogen gas bearings can be improved by increasing the ambient pressure, reducing the gas film clearance, and raising the bearing eccentricity ratio. Meanwhile, the critical mass increases, and the bearing dynamic stability is enhanced.

Frost usually grows on the cooling surface of heat transfer equipment, which often operates under different working pressures. In such conditions, one of the fundamental influencing factors of frosting, the diffusion coefficient of water vapor around the cooling surface, is different from that in the normal atmosphere pressure. In order to investigate the pressure effect on frosting, a test rig for frosting visualization is designed. The role of working pressure around the cooling surface on the frost crystal morphologies and frost layer characteristics is evaluated under different air parameters and temperatures of cooling surface. The vertical growth and lateral distribution of frost crystals are strongly related to working pressure around the cooling surface. More frost crystal morphologies and faster growth rate of frost layer are presented at a lower pressure. The frost thickness, frost accumulation and density reduce with higher pressure. The dimensionless correlation of frost thickness is proposed considering working pressure around the cooling surface, humid air parameters, and temperature of cooling surface.

The hydrogen hydrostatic thrust bearing (HHTB) is a key component of hydrogen liquefaction that impacts turbo-expander characteristics. To analyze the feasibility of using the HHTB in this application, characteristics of HHTBs were calculated using a CFD model. To upgrade the performance of the HHTB, the impacts of bearing structure and operating parameters on static performance were investigated. Dynamic characteristics of the HHTB were studied using the dynamic grid method. It was found that the load capacity of the HHTB is less than that of helium-lubricated bearings but higher than that of air- and methane-lubricated bearings. The turbulent kinetic energy of hydrogen is higher than that of other gases. Load capacity can be enhanced through boosting supplied pressure, expanding the diameter of supply orifices, reducing gas film clearance, increasing the orifices quantity and setting a circumferential groove. A reduction in disturbance amplitude slightly increased the bearing’s dynamic stiffness. The dynamic stability of the HHTB was improved by a small film clearance in response to disturbance.

In cryogenic fluid storage and delivery, the rapid contraction and rebound of bubbles are prone to occur during bubble collapse due to the pressure saltation. With the contraction and rebound of bubbles, the pressure and temperature in the bubbles fluctuate greatly, which affects the service life of fluid machinery. During bubble contraction and rebound, there is an accompanied complex heat and mass transfer process. According to the thermal properties of cryogenic fluids, a single-bubble collapse model is proposed considering the temperature variations inside the bubble. In order to study the variation in temperature and pressure during bubble collapse in cryogenic fluids, the contraction and rebound of a single bubble in liquid hydrogen are investigated numerically under various operating pressures and supercooling degrees. The numerical results of the model indicate that there are periodic contraction and rebound of the bubble when the pressure rises suddenly. Furthermore, the periods and attenuation rates of bubbles in different media are studied and compared. For the most concerned pressure and temperature characteristics, the relationship between the peak pressure, the attenuation rate of the temperature and the dimensionless number is proposed.