# Study on the Performance of Liquid Metal Lubricated V-Groove Bearing Considering Turbulence
## 1 Introduction  
Computed tomography (CT) equipment can find the internal problems of the object before the implementation of measures. It can reduce the cost and risk, and plays an increasingly important role in medical diagnosis, equipment diagnosis, and other aspects. As the high-value and consumable parts of CT machines, one or two CT are generally needed to be replaced once a year per CT equipment. Therefore, to medical giants in various countries, CTT is the core component in the development and production process of CT machines [1] and has a great market value. In order to avoid the local damage of a fixed anode due to heat accumulation in the CTT, a mature technology is to use a rotating anode instead of a fixed one, so that the heat will be dispersed into an arc area, and not a point, preventing materials from local damage. Considering the actual working conditions of CTT, it is required that the lubricant used in the rotating anode should not pollute the vacuum tube. The lubricant should also be able to withstand high temperature and conduct electricity. Meanwhile, it is better to conduct heat. Gallium based liquid metal (GBLM) has excellent electric and thermal conductivity as well as fluidity. These qualities make it the best choice to lubricate the rotating anode. In the Netherlands, the Philips Medical Institution has produced the IMRC CTT [1]. This CTT changed the anode applied to medical diagnosis from fixed to rotating, and used a spiral groove anode bearing with LM as the lubricant. This technology has not only improved the performance of CTT, but also broadened the research field. Next, the technology was developed, comparatively well-established in Europe and America [2, 3, 4, 5]. Professor [PERSON] of Xi'an Jiaotong University in China [6] provided a detailed design and research on this type of LM lubricated spiral groove bearing. GBLM has the advantages of low vapor pressure, high thermal conductivity, and good fluidity, but is also non-toxic and stable in thermo-physical properties. The research on GBLM is increasing, especially its lubrication performance, and its application is growing extensively [7]. For example, [PERSON] [8] used LM as a high temperature conductive lubricating fluid in magnetohydrodynamic bearings for nuclear power, and found that the bearings' capacity had been greatly improved; [PERSON] [9] used gallium-indium-tin liquid metal (G-I-T LM) to lubricate and found that the resistance and calorific value of the brush with high current density decreased; [PERSON] [10] discovered that GBLM could lubricate deep groove ball bearings in an oxygen free environment, at the same time, the surface tension and adhesion of GBLM had a great influence on the lubrication performance; [PERSON] [11] studied the lubrication properties of LM at different temperatures; [PERSON]'s research [12] showed that GBLM could effectively prevent the welding of sliding interface under extreme pressure and high load; and [PERSON]'s team [13; 14; 15; 16] has conducted many friction and wear tests, showing that a GBLM oxide film has a certain lubricating effect. The research of spiral groove bearing has a history of more than 90 years [17]. Due to the spiral groove bearing's self-sealing performance, this kind of bearing does not need external oil supply equipment. The hydrodynamic sliding bearing realizes load carrying through the dynamic pressure oil film. Due to the special structure of the spiral groove bearing, this kind of bearing forms an oil film by the pumping pressure effect and periodic step effect of the spiral groove. Compared with the traditional ball bearing used in CTT, the spiral groove bearing has many advantages such as compact structure, good stability, low vibration noise, low friction power consumption, low wear, and long service life [17]. Therefore, it can better meet the needs of high-speed and stable rotation of the anode target.