Fluid lubricated bearings have been widely adopted as support components for high-end equipment in metrology, semiconductor devices, aviation, strategic defense, ultraprecision manufacturing, medical treatment, and power generation. In all these applications, the equipment must deliver extreme working performances such as ultraprecise movement, ultrahigh rotation speed, ultraheavy bearing loads, ultrahigh environmental temperatures, strong radiation resistance, and high vacuum operation, which have challenged the design and optimization of reliable fluid lubricated bearings. Breakthrough of any related bottlenecks will promote the development course of high-end equipment. To promote the advancement of high-end equipment, this paper reviews the design and optimization of fluid lubricated bearings operated at typical extreme working performances, targeting the realization of extreme working performances, current challenges and solutions, underlying deficiencies, and promising developmental directions. This paper can guide the selection of suitable fluid lubricated bearings and optimize their structures to meet their required working performances.

Due to their exceptional static and dynamic properties along with high-temperature resistance, liquid metal bearings are extensively employed in challenging environments. This paper carried out a multi-objective optimization work for spiral groove journal liquid metal bearings (JLMB) by using a NSGA-II. The clearance of bearing C, spiral angle a, groove depth hg, groove ridge ratio β, groove number N, and groove spacing P were chosen as design variables to maximize the load-carrying capacity and the effective stiffness of liquid metal bearing. During optimization process, the Latin hypercube sampling was adopted to generate 41 sample points, and the Kriging surrogate model was used to establish the correlations between design variables and objective functions. The Pareto front with optimal structures was obtained after optimization. Subsequently, optimal parameters were determined from the Pareto front by using the TOPSIS decision method. Finally, a comparative analysis of bearing performance was conducted between the journal liquid metal bearings with optimal parameters and the original parameters. The results indicated that the optimal JLMB parameters are given as follows: C = 10 μm, a = 26°, hg = 5.2 μm, β = 0.7, P = 11.1 mm, N = 10. The static and dynamic performance of optimized JLMB has been significantly improved. Specifically, the load carrying capacity increased to 2781.2N, making a 1313% enhancement over the JLMB with original parameters. While the effective stiffness of the optimized JLMB surged to 1.86 × 108 N/m, a more than 20-fold increase.

Vortex generators can boost heat transfer performance greatly, although they are always linked with significant pressure drops. In this article, to reduce the pressure drop while improving the thermal efficiency simultaneously, traditional delta winglet pair vortex generators (DWPVG) with slits are installed in the rectangular channel. Besides, the effects of slits on DWPVG on pressure drops and heat transfer performances for different Reynolds numbers are studied. To reveal the fluid flow characteristics, three-dimensional calculations using a confirmed turbulence model are undertaken and the underlying thermo-fluid processes are exposed for the various investigated cases. To reveal the overall thermal performance of different cases, two overall thermal performance factors Nuave/Nu0/(f/f0) and Nuave/Nu0/(f/f0)1/3 are used. The findings suggest that when the fluid flows through slits, induced vortices are located closer to the bottom surface, generating an improvement of the local Nusselt number behind DWPVG. Furthermore, DWPVG with slits can decrease the pressure drop, but also make the local thermal efficiency improve in the channel with a high blocking ratio. Moreover, the increase in the overall thermal performance of the slit DWPVG channel with a high blocking ratio is enlarged with the Reynolds number raise. Besides, the highest heat transfer enhancement is provided by opening slits on five DWPVGs in the rectangular channel.

Liquid metal is a perfect lubricant due to its low melting point, good fluidity at room temperature, higher thermal conductivity and high temperature stability. In this work, the novel hydrodynamic liquid metal bearing with spiral grooves is studied. Influences of the eccentricity, the bearing radius clearance, and the groove structural parameters on the pressure distributions and the load carrying capacity of journal liquid metal bearing are deeply numerically investigated. Meanwhile, the bearing clearance and the structure parameter of herringbone grooves on pressure distribution and load carrying capacity of thrust liquid metal bearing are also numerically conducted and experimentally validated. Numerical studies are conducted based on the finite element method. Results show that the pressure distribution and the load carrying capacity of journal liquid metal bearing are significantly affected by the eccentricity, the bearing clearance and the groove structural parameters. Specifically, for journal bearing, the load carrying capacity increases with the growth of the eccentricity and the groove spacing, while it decreases with the increase of radius clearance, the groove depth and the groove ridge ratio. Besides, it turns out that when the spiral angle is larger than 37.5 degree, the increase of the groove spiral angle results in a decrease of the load carrying capacity, while when the spiral angle is lower than 37.5 degree, the value of load carrying capacities at different spiral angle depends on the specific value of eccentricity. As for thrust bearing, the load carrying capacity increases with the decrease of bearing clearance, and the increase of groove depth. Besides, the groove numbers of 13 and the angle between two vertices of herringbone groove of 13 degree are beneficial for improving the load carrying capacity of thrust liquid metal bearings. Based on the above observations, optimal design parameter sets are selected to obtain much higher load carrying capacities up to four times for both journal and thrust bearings compared with the bearings with original parameters.