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Foil bearing is considered to be a promising supporting technology in high-speed centrifugal machinery. Due to the high-speed shearing effect in the viscous lubricant film, heat generation could not be ignored. In this paper, a thermo-elastic model of the multi-leaf foil thrust bearing is proposed to predict its thermal and static characteristics. In the model, modified Reynolds equation, energy equation, and Kirchhoff equation are solved in a coupling way. The contact area between the foil and welding plate is taken into account. Besides, the effect of cooling air on the bearing temperature is investigated. The ultimate load capacity and transient overload failure process of the bearing is analyzed and discussed. The effect of rotation speed on the bearing temperature is more obvious than that of the bearing load. The bearing temperature drops obviously by introducing the cooling air, and the cooling effect is improved with the supply pressure. The transient overload failure of the bearing occurs when the bearing load exceeds the ultimate value.

Perovskite barium stannate (BaSnO3) is a promising candidate that can be used as transparent conducting oxide in optoelectronic devices and as the channel material in high-mobility oxide electronics. In this work, we calculate the lattice thermal conductivity and investigate the impact of point defects on thermal transport in BaSnO3based on the phonon Boltzmann transport equations with interatomic force constants from first-principles calculations. In pristine BaSnO3, we find the contribution of acoustic phonons to thermal transport accounts for 54% at 300 K and the rest is attributed to the lower-frequency (27.5–50 THz) optical modes with relatively high group velocity. We show oxygen vacancies and impurities can cause noticeable reduction in thermal conductivity of BaSnO3, but the corresponding mechanisms differ in terms of scattering rates on different phonon modes. The thermal conductivity reduction due to oxygen vacancies at 300 K is mainly caused by the increased scattering of the acoustic phonons and the low-frequency optical phonons. Lanthanum and potassium impurities mainly increase the scattering of acoustic phonons, but antimony impurity lowers the thermal conductivity by increasing the scattering rate of dominant phonons, including both the acoustic modes and the low-frequency optical modes. The results and findings facilitate us to better understand the thermal transport mechanisms of perovskite oxides with an emphasis on the impact of oxygen vacancies and impurities on the thermal properties of BaSnO3.

The multilayer protuberant foil bearing, as a new type of compliant surface foil bearing, shows a great and wide application promise. Six pads multilayer protuberant foil thrust bearings with different configurations were designed and fabricated in this study. The static characteristics of these bearings and the effects of their key configuration parameters including the thickness of top foil, the thickness of protuberant foil, and the layers of protuberant foil are investigated. The experimental results reveal that the bearings show nonconstant structural stiffness, and the stiffness mainly depends on both the load force and the configuration of the bearings. In the airborne regime, the torque of the bearing is mainly dependent on the load force rather than the rotational speed, which can be interpreted by the proportional relationship between the bearing clearance and the rotational speed. Furthermore, the experimental results also show that the maximum load capacities of the bearing are also greatly affected by the bearing configuration. With more layers of the protuberant foils and thinner top foil, the bearing shows larger maximum load capacity. The work provides some insights about the relationships between the characteristics and the configuration of the bearings.

In this paper, the hydrodynamic performance of a new double-layered protuberant gas foil journal bearing (DPGFB) was experimentally studied in a high-speed turbo-expander and compared with the conventional Hydresil foil journal bearing (HGFB). The material properties of supporting foils are important for the bearing performance such as load capacity and frictional damping. In both DPGFBs and HGFBs, two types of materials, stainless steel (0Cr18Ni9) and beryllium bronze (QBe1.7), have been used as supporting foil materials, and their effects on the bearing performance were discussed. A stable operation of turbo-expander with rotational speed up to 70,000 rpm was achieved in the tests of both of two types of bearings. Due to the larger stiffness of the foil layer, the DPGFBs had larger lift-off speed and larger gas film friction torque than HGFBs at high speed when the same foil material was used. The comparison showed that the bearings using 0Cr18Ni9 had a larger life-off friction torque. The synchronous vibration amplitudes of the rotors during the high speed operation and the shut-down process were smaller for DPGFBs than HGFBs, which indicated that the DPGFBs had a better damping performance than HGFBs.

The supporting stiffness and coulomb damping in a bearing play significant roles in the smooth operation of rotor-bearing system. The performance of multi-decked protuberant gas foil journal bearing is evaluated experimentally in a high-speed turboexpander. The effect of radial clearance on the bearing performance is analyzed based on the relationship between rotor speed and supply pressure in the speed-up and speed-down processes. The maximal speed of the 25 mm diameter rotor reached as high as 100 kr/min, and subsynchronous vibrations are suppressed in the tests. For the bearings with 0.05 mm protuberant foils, there will be thermal runaway problem with −20 µm clearance, while unstable operation appears with 80 µm clearance. For the bearing with 0.07 mm protuberant foil, the vibration amplitude is constrained within smaller amplitude due to stiffer supporting structure. The test results indicate that the bearing can operate stably under different gas film thickness and supporting stiffness, and that this kind of foil bearing can be applied in high-speed turbomachinery due to its stability and adaptability.

Coal-bed methane (CBM) reserves are rich in Sinkiang of China, and liquefaction is a critical step for the CBM exploration and utilization. Different from other CBM gas fields in China, CBM distribution in Sinkiang is widespread but scattered, and the pressure, flow-rate and nitrogen content of CBM feed vary significantly. The skid-mounted liquefaction device is suggested as an efficient and economical way to recover methane. Turbo-expander is one of the most important parts which generates the cooling capacity for the cryogenic liquefaction system. Using turbo-expander, more cooling capacity and higher liquefied fraction can be achieved. In this study, skid-mounted CBM liquefaction processes based on Claude cycle are established. Cryogenic turbo-expander with high expansion ratio is employed to improve the efficiency of CBM liquefaction process. The unit power consumption per liquefaction mole flow-rate for CBM feed gas is used as the object function for process optimization, compressor discharge pressure, flow ratio of feed gas to turbo-expander and nitrogen friction are analyzed, and optimum operation range of the liquefaction processes are obtained.