Liquid metal lubricating system, monitoring method and mechanical equipment

Abstract

The invention discloses a liquid metal lubricating system, a monitoring method and mechanical equipment, and relates to the technical field of engine lubrication. The liquid metal lubricating system comprises a bearing assembly and a liquid metal lubricant, gaps of the bearing assembly are filled with the liquid metal lubricant, the liquid metal lubricant contains rare earth elements, the bearing assembly comprises a retainer, the retainer is arranged in a raceway and used for separating and guiding a rolling body, and the interior of the retainer is provided with a gradient pore structure. The porosity of the gradient pore structure is continuously reduced in the direction from the bearing inner ring to the bearing outer ring, and the gradient pore structure is used for driving the liquid metal lubricant to flow back from the outer side area with the low porosity to the inner side area with the high porosity in a centrifugal force field generated by rotation of the bearing assembly. The liquid metal lubricating system, the monitoring method and the mechanical equipment are used for achieving stable and long-acting lubrication of the bearing in the mechanical equipment under the ultra-high-temperature working condition.

Description

Technical Field

[0001] This disclosure relates to the field of engine lubrication technology, and in particular to a liquid metal lubrication system, monitoring method, and mechanical equipment. Background Technology

[0002] As aero-engines evolve towards higher thrust-to-weight ratios and thermal efficiency, the operating environment of their core component, the main bearing, becomes extremely harsh, with operating temperatures often exceeding 400°C and instantaneous temperatures even reaching over 1000°C. In this temperature range, the synthetic hydrocarbon or ester-based lubricating oils widely used in traditional aero-engines undergo severe thermal oxidation reactions, leading to increased viscosity, decreased lubrication performance, and the formation of acidic substances and solid coking deposits. These coking deposits can clog oil passages, disrupt the continuity of the lubricating oil film, and ultimately cause serious failures such as accelerated bearing wear, overheating, and even seizure.

[0003] Liquid metal lubrication technology, which remains liquid at high temperatures, has become a solution to ultra-high temperature lubrication problems. However, directly applying existing liquid metal lubrication technology to aero engines can lead to component volatilization, crystallization, or harmful reactions with bearing materials at ultra-high temperatures, generating impurity particles. Furthermore, it can easily leak along sealing gaps, contaminating the engine. Summary of the Invention

[0004] This disclosure is made in view of the above-mentioned problems. This disclosure provides a liquid metal lubrication system, monitoring method, and mechanical equipment, which achieves stable and long-term lubrication of bearings in mechanical equipment under ultra-high temperature conditions. Simultaneously, it can accurately monitor the lubrication status in real time, provide timely warnings of lubrication failures, and improve the reliability and safety of mechanical equipment operation.

[0005] To achieve the above objectives, according to one aspect of this disclosure, the following technical solution is provided:

[0006] A liquid metal lubrication system includes: a bearing assembly and a liquid metal lubricant, wherein the liquid metal lubricant fills the gaps in the bearing assembly, and the liquid metal lubricant contains rare earth elements; The bearing assembly includes an inner bearing ring, an outer bearing ring, multiple rolling elements, and a cage. The multiple rolling elements are located within a raceway formed by the inner and outer bearing rings. The cage is disposed within the raceway to separate and guide the rolling elements. The cage has a gradient porosity structure inside, with the porosity continuously decreasing along the direction from the inner to the outer bearing ring. The gradient porosity structure is used to drive the liquid metal lubricant to flow back from the outer region with low porosity to the inner region with high porosity in the centrifugal force field generated by the rotation of the bearing assembly.

[0007] According to another aspect of this disclosure, a method for monitoring the lubrication condition of a liquid metal lubrication system is provided, comprising: Obtain the resistance signal of the liquid metal lubricant and the ultrasonic signal inside the bearing assembly; Determine whether the current change in the resistance signal exceeds a first threshold. Determine whether the current change in the ultrasonic signal exceeds a second threshold; When the current change in the resistance signal exceeds the first threshold and the current change in the ultrasonic signal exceeds the second threshold, a lubrication failure is determined in the liquid metal lubrication system and a warning signal is generated.

[0008] According to another aspect of this disclosure, a mechanical device is also provided, which employs the liquid metal lubrication system described in the first aspect.

[0009] Compared with existing technologies, the present disclosure provides one or more technical solutions, firstly, by adding rare earth elements to the liquid metal lubricant, the rare earth elements can form a stable alloy phase with the liquid metal, inhibiting the volatilization and crystallization of components in the liquid metal at ultra-high temperatures. Simultaneously, the rare earth elements can form a dense rare earth passivation film on the surface of the bearing material, isolating the liquid metal from direct contact with the bearing matrix material and preventing harmful chemical reactions. This effectively solves the problems of easy volatilization and crystallization of existing liquid metals and the generation of impurities through reactions with bearing materials, ensuring the purity of the lubricating medium and the stability of its lubrication performance. Secondly, by structurally designing the cage to form a gradient pore structure with continuously decreasing porosity from the inner ring to the outer ring, the centrifugal force field generated by the rotation of the bearing assembly drives the liquid metal lubricant to flow back from the low-porosity outer region of the outer ring to the high-porosity inner region of the inner ring, achieving self-circulation and recovery of the liquid metal lubricant. This reduces the leakage of liquid metal along the sealing gap, avoids internal contamination of mechanical equipment, and improves the sealing performance of liquid metal lubrication technology in aero-engine applications. Furthermore, the lubrication condition monitoring method disclosed herein combines the resistance signal of the liquid metal lubricant and the ultrasonic signal of the bearing assembly for dual-signal collaborative judgment. It utilizes the fact that the resistance characteristics of the liquid metal lubricant change with its composition, purity, and distribution, and that the ultrasonic signal can reflect the contact state of the bearing raceway and rolling elements and the integrity of the lubrication film, to achieve accurate real-time monitoring of the lubrication system status. Compared with single-signal monitoring, it effectively avoids the problems of misjudgment and missed judgment, can promptly detect lubrication faults and generate early warning signals, and facilitates timely response measures by staff.

[0010] Based on this, the liquid metal lubrication system disclosed herein is applied to mechanical equipment, such as aero engines, to meet the ultra-high temperature conditions of aero engine main bearings. It breaks through the temperature limitations of traditional lubricating oils and solves the defects of existing liquid metal lubrication. Combined with lubrication status monitoring, it significantly improves the lubrication reliability of aero engine main bearings under ultra-high temperature conditions, thereby improving the overall operational stability and service life of aero engines. Attached Figure Description

[0011] The accompanying drawings, which are included to provide a further understanding of this disclosure and form part of this disclosure, illustrate exemplary embodiments of the present disclosure and are used to explain the disclosure, but do not constitute an undue limitation of the disclosure. In the drawings: Figure 1 A schematic cross-sectional view of a liquid metal lubrication system provided in an exemplary embodiment of this disclosure is shown.

[0012] Figure 2 A partial view of a bearing assembly provided in an exemplary embodiment of this disclosure is shown.

[0013] Figure 3a A partial view of the sealing structure provided in an exemplary embodiment of the present disclosure at room temperature is shown.

[0014] Figure 3b A partial view of the sealing structure provided in an exemplary embodiment of this disclosure at a high temperature is shown.

[0015] Figure 4 A flowchart is shown for a method for monitoring the lubrication status of a liquid metal lubrication system provided in an exemplary embodiment of this disclosure.

[0016] Figure 5 A detailed flowchart of a lubrication condition monitoring method for a liquid metal lubrication system provided in an exemplary embodiment of this disclosure is shown.

[0017] Figure label: 110-Bearing assembly, 111-Bearing inner ring, 112-Bearing outer ring, 113-Rolling element, 114-Cage, 115-Sealing structure, 1151-First seal, 1152-Second seal, 1153-Shape memory alloy element, 120-Liquid metal lubricant, 130-Resistance sensor, 140-Ultrasonic sensor, 150-Temperature sensor. Detailed Implementation

[0018] To facilitate a clear description of the technical solutions in the embodiments of this disclosure, the terms "first" and "second" are used to distinguish identical or similar items with substantially the same function and effect. For example, the first threshold and the second threshold are merely used to distinguish different thresholds and do not limit their order. Those skilled in the art will understand that the terms "first" and "second" do not limit the quantity or execution order, and the terms "first" and "second" are not necessarily different.

[0019] It should be noted that in this disclosure, the terms "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in this disclosure should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0020] In this disclosure, "at least one" means one or more, and "more than one" means two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c can mean: a, b, c, a combination of a and b, a combination of a and c, a combination of b and c, or a, b, and c, where a, b, and c can be single or multiple.

[0021] Aero engines are the core power components of modern aircraft. Their main bearings need to operate stably for a long time under high temperature, high speed, high load and complex variable conditions. The performance of the lubrication system directly determines the reliability, lifespan and even the safety of the entire engine. At present, synthetic lubricating oil is generally used for lubrication of aero engine main bearings.

[0022] However, with the continuous improvement of engine thrust-to-weight ratio and thermal efficiency, the working environment of main bearings is becoming increasingly harsh. Traditional oil lubrication technology has revealed the following significant defects: First, poor high-temperature stability and easy coking. The operating temperature of high-pressure turbine bearings in modern advanced aero engines often exceeds 200°C, with even higher local peak temperatures. At this high temperature, synthetic lubricating oil will undergo violent thermal oxidation and decomposition, generating solid deposits such as varnish and carbon deposits. Coking deposits will adhere to and block the bearing raceway, lubrication nozzles, and oil return lines, leading to a deterioration in lubrication and cooling effects, forming a vicious cycle, and ultimately causing bearing overheating, abnormal wear, or even seizure failure, seriously restricting the development of engines to operate at higher temperatures. Second, insufficient adaptability to extreme operating conditions. Aero engines experience extremely high speeds (thousands to nearly 20,000 revolutions per minute), intense maneuvering flight attitude changes, and extremely wide operating temperature ranges during operation. The enormous centrifugal force generated by high-speed rotation can easily throw lubricating oil away from the lubrication contact area, damaging the integrity of the oil film. Extreme conditions may lead to momentary interruption of oil supply. Furthermore, a wide temperature range places extremely high demands on the viscosity-temperature characteristics of the lubricating oil. Therefore, traditional lubrication systems struggle to maintain a stable and reliable lubrication state under these combined extreme conditions. Third, condition monitoring and health management capabilities are lagging. Current lubrication systems rely heavily on macroscopic parameters such as lubricating oil pressure, temperature, and flow rate. These parameters can only indirectly and laggingly reflect the system status, failing to monitor the microscopic lubrication film condition and early wear signs within the bearing in real time. This results in maintenance strategies being primarily reactive or periodic, hindering condition-based predictive maintenance, increasing total life-cycle costs, and creating safety hazards.

[0023] To overcome the high-temperature bottleneck of oil lubrication, liquid metals (such as gallium-based alloys) have attracted attention as a novel high-temperature lubricating medium in recent years. However, directly applying existing liquid metal lubrication technologies to aero-engines still faces technical obstacles. First, the upper temperature limit of existing liquid metal lubricants is orders of magnitude lower than the requirements of aero-engines. Existing liquid metal formulations, such as Ga-In binary alloys, are typically designed for operating temperatures not exceeding 600°C. In contrast, the operating temperature range of aero-engine main bearings can reach 400°C to over 1200°C. Under these ultra-high temperature conditions, existing liquid metals are prone to component volatilization, thermal decomposition, or harmful chemical reactions with bearing materials, leading to rapid degradation of their lubrication performance and failing to meet the requirements for long service life and high reliability. Second, there is a lack of reliable sealing solutions suitable for the high-speed, high-pressure conditions of aero-engines. Liquid metals have low viscosity, high density, and strong wettability, making them highly susceptible to leakage under the strong centrifugal force generated by high-speed rotation and the pressure difference inside the engine. Traditional labyrinth seals and face seals used for oil lubrication are severely inadequate in terms of sealing performance and durability when exposed to molten metal. Leaks not only lead to lubricant loss but also contaminate other precision engine components, causing secondary malfunctions.

[0024] To overcome the above problems, this disclosure provides a liquid metal lubrication system, monitoring method, and mechanical equipment. It solves the problems of easy volatilization and crystallization, harmful reaction with bearing materials, leakage and pollution, and inaccurate monitoring of lubrication status in existing liquid metal lubrication technologies under ultra-high temperature conditions of aero-engines. It achieves stable and long-term lubrication of aero-engine main bearings under ultra-high temperature conditions, and can monitor the lubrication status in real time and provide timely warnings of lubrication failures, thereby improving the reliability and safety of aero-engine operation.

[0025] It should be understood that the aforementioned liquid metal lubrication system can be used not only for aero-engine bearings, but also extended to various rotating mechanical devices that need to operate reliably for a long time under extreme high temperature, high speed and harsh environment, including but not limited to the main shaft support of gas turbines, precision bearings of high-speed motors, high temperature transmission mechanisms of special industrial compressors and special rotating equipment in vacuum or strong radiation environments.

[0026] Figure 1 A schematic cross-sectional view of a liquid metal lubrication system provided in an exemplary embodiment of this disclosure is shown. Figure 1 As shown, the liquid metal lubrication system provided in this embodiment includes a bearing assembly 110 and a liquid metal lubricant 120. The liquid metal lubricant 120 fills the gaps in the bearing assembly and contains rare earth elements. By filling the gaps in the bearing assembly 110 with the rare earth-containing liquid metal lubricant 120, the rare earth elements are used to suppress the volatilization and crystallization of liquid metal under the ultra-high temperature conditions of aero-engines, and harmful reactions between the liquid metal and the bearing matrix are avoided. This ensures the stability and purity of the lubricating medium, breaks through the high-temperature usage limitations of traditional lubricating oils, and is suitable for the harsh working environment of main bearings.

[0027] In one feasible embodiment, the bearing assembly 110 includes an inner bearing ring 111, an outer bearing ring 112, multiple rolling elements 113, and a cage 114. The multiple rolling elements 113 are located within the raceway formed by the inner bearing ring 111 and the outer bearing ring 112. The cage 114 is disposed within the raceway to separate and guide the rolling elements 113. The standardized assembly structure of the inner bearing ring 111, outer bearing ring 112, rolling elements 113, and cage 114, combined with the separation and guiding function of the cage 114 on the rolling elements 113, ensures the stability and accuracy of the rotation of the bearing assembly 110, reduces direct friction and wear between the rolling elements 113, and the filling of each mating gap by the liquid metal lubricant 120 forms a comprehensive lubricating film, significantly reducing the coefficient of friction at each contact point of the bearing, improving the overall lubrication effect, and providing dual protection of structure and lubrication medium for the reliable operation of the main bearing of the aero-engine.

[0028] When aircraft engine bearings rotate at high speeds, they generate enormous centrifugal force, which makes it easy for liquid metal lubricant to be thrown to the outside of the bearing, resulting in insufficient lubrication of the inner rolling elements and raceways.

[0029] Based on this Figure 2 A partial view of a bearing assembly provided in an exemplary embodiment of this disclosure is shown. (As...) Figure 2 As shown, in the bearing assembly provided in this embodiment, the cage 114 has a gradient porosity structure inside. Along the radial direction from the inner ring 111 to the outer ring 112 of the bearing, the porosity of the gradient porosity structure continuously decreases. The gradient porosity structure is used to drive the liquid metal lubricant to flow back from the outer region with low porosity to the inner region with high porosity in the centrifugal force field generated by the rotation of the bearing assembly 110.

[0030] Specifically, the aforementioned gradient porosity structure exhibits a continuously decreasing porosity distribution along the radial direction from the inner ring 111 to the outer ring 112 of the bearing. Utilizing the centrifugal force field generated when the bearing assembly 110 rotates, it creates a directional backflow driving force for the liquid metal lubricant, propelling the lubricant from the outer region of the bearing outer ring 112 (low porosity) to the inner region of the bearing inner ring 111 (high porosity). This achieves autonomous circulation and recovery of the liquid metal lubricant, effectively reducing lubricant leakage along the sealing gap. Simultaneously, it ensures uniform distribution of the lubricating medium within the bearing assembly, continuously providing effective lubrication to all friction contact points, thus meeting the long-term stable lubrication requirements of aero-engines under ultra-high temperature conditions.

[0031] Specifically, from the inner side (near the bearing rotation axis) to the outer side (far from the axis) of the cage 114, its porosity gradually and continuously decreases from a high value (e.g., 55%) to a low value (e.g., 25%). This gradient porosity design, combined with the wettability of the cage material, creates a capillary pressure gradient within the cage. Due to the higher porosity inside and lower porosity outside, the resulting capillary pressure difference (which can be designed to be ≥200 Pa) drives the liquid metal to flow back from the outer side (high centrifugal force zone) to the inner side (low centrifugal force zone) of the bearing. This disclosure reverses the direction of the cage porosity gradient with the direction of the centrifugal force field generated when the bearing rotates, making the cage 114 itself act as a capillary pump, actively counteracting the centrifugal force and pumping the liquid metal thrown outward back to the inner lubrication area. This achieves a self-pumping function for returning liquid metal. This design does not require additional external power; relying solely on the structural characteristics of the cage itself, it effectively solves the lubrication problem under high centrifugal force conditions, ensuring uniform distribution and continuous supply of lubricant.

[0032] For example, the cage 114 described above is integrally formed using selective laser melting (SLM) additive manufacturing technology.

[0033] In some examples, the aforementioned liquid metal lubricants also include gallium, indium, and zinc. The liquid metal lubricant is a ternary eutectic or near-eutectic alloy system based on gallium-indium-zinc, with each element playing a synergistic regulatory role. Gallium, as the main component of the system, leverages its low melting point and wide liquid phase range to ensure the lubricant maintains a stable liquid phase across a broad operating temperature range, from room temperature to the ultra-high temperature of aero-engine main bearings, meeting the basic morphological requirements for lubrication under all operating conditions. Indium has high surface activity, significantly improving the spreading and adhesion (i.e., wettability) of the liquid alloy on the bearing steel surface and forming an indium-rich surface layer, enhancing its resistance to oxidation and corrosion. The introduction of zinc, existing in the liquid matrix as specific clusters or short-range ordered structures, effectively increases the overall viscosity and shear strength of the alloy, thereby enhancing the liquid film's load-bearing capacity and impact resistance under high pressure. At high temperatures, zinc can also form a more stable coordination structure with gallium, inhibiting the thermal migration and volatilization of gallium atoms through a pinning effect, maintaining the long-term stability of the alloy composition. Through the synergistic effect of these four components, the lubricant disclosed herein maintains excellent fluidity while possessing higher thermal stability, stronger load-bearing capacity, and better material compatibility, thus meeting the extreme operating conditions required for aero-engine bearings.

[0034] For example, based on a 100% mass percentage of liquid metal lubricant, gallium accounts for 65%–70% of the mass percentage, indium for 20%–25% of the mass percentage, zinc for 9.5%–9.9% of the mass percentage, and rare earth elements for 0.1%–0.5% of the mass percentage. Liquid metal lubricants with this formulation exhibit both excellent high-temperature fluidity and structural stability. Trace amounts of rare earth elements are uniformly dispersed in the alloy matrix in nano-particle form, without significantly affecting the system's low viscosity and flow characteristics. Simultaneously, they effectively suppress the volatilization and crystallization of matrix components under ultra-high temperature conditions. Furthermore, rare earth particles can form a dense surface passivation protective layer on the bearing contact surface through physical adsorption or chemical action during friction. This prevents harmful alloying reactions or chemical corrosion between the liquid metal and the bearing material, while also providing auxiliary effects in friction reduction and wear resistance. This balances lubrication reliability under high-temperature conditions, material chemical stability, and overall cost-effectiveness, making it suitable for the lubrication requirements of aero-engine main bearings under long-term high-temperature and high-speed operation.

[0035] In one example, the aforementioned rare earth element, yttrium, is uniformly dispersed in a liquid metal lubricant in the form of nanoparticles. When rare earth elements are uniformly dispersed in liquid metal lubricants in the form of nanoparticles (typically with a particle size between 10-100 nanometers), several beneficial effects can be achieved. First, the nano-yttrium particles can act as miniature bearings, rolling or sliding between the surfaces of the friction pair, thereby significantly reducing the coefficient of friction and improving lubrication performance. Second, these nanoparticles have a high specific surface area and surface activity, enabling them to form a physical adsorption film or chemical reaction film on the bearing surface. This protective film can effectively isolate the direct contact of the friction pair, reduce wear, and improve load-bearing capacity. More importantly, the addition of these nanoparticles can significantly improve the overall thermophysical properties of the liquid metal, such as increasing thermal conductivity, which helps to quickly remove the heat generated by the bearing, thus playing a role in heat dissipation. Furthermore, rare earth elements can also undergo microalloying with other elements in the liquid metal lubricant, refining the grain size, improving the chemical stability of the liquid metal lubricant, and further inhibiting oxidation and volatilization at high temperatures.

[0036] In some examples, embodiments of this disclosure also provide a method for preparing the above-mentioned liquid metal lubricant to ensure that the components are fully mixed, particularly to achieve the nano-sizing and uniform dispersion of the rare earth element yttrium. This preparation method mainly includes the following steps: The first step is raw material preparation and pretreatment: accurately weigh high-purity gallium, indium, and zinc metal raw materials, as well as nano-sized rare earth element yttrium powder, according to the aforementioned mass ratio. All raw materials must be cleaned before use to remove surface oxides and impurities.

[0037] The second step, preliminary melting and alloying: The weighed gallium, indium, and zinc metals are placed in a melting furnace under an inert atmosphere (such as argon). The temperature is slowly raised to slightly above the melting point of zinc (about 450°C) and maintained at this temperature for a period of time. At the same time, mechanical or electromagnetic stirring is used to ensure that the three metals are fully melted and mixed evenly to form a homogeneous Ga-In-Zn ternary alloy liquid.

[0038] The third step is the addition and dispersion of nanoparticles: Pre-weighed nano-sized yttrium powder is slowly added to the molten alloy liquid. During the addition process, vigorous stirring is continuously performed to promote the initial dispersion of the nanoparticles.

[0039] The fourth step is ultrasonic dispersion: The molten alloy containing yttrium nanoparticles is transferred to a specialized container equipped with an ultrasonic generator. The ultrasonic generator is activated, utilizing the cavitation effect of high-frequency (e.g., 20kHz~40kHz) sound waves in the liquid. This strong cavitation effect, microjets, and shock waves generated in the liquid metal effectively break up the agglomerates of nanoparticles and drive them to distribute uniformly throughout the liquid metal matrix. The time and power of the ultrasonic dispersion process need to be optimized based on the specific alloy quantity and equipment parameters to ensure the best dispersion effect.

[0040] Step 5, Cooling and Shaping: After thorough ultrasonic dispersion, the prepared liquid metal lubricant is slowly cooled to room temperature under an inert atmosphere and injected into a dedicated storage container as needed for subsequent use.

[0041] The liquid metal lubricant prepared by the above method can achieve highly uniform and stable dispersion of rare earth nanoparticles in the liquid metal matrix, thereby ensuring that it can still exert the preset comprehensive performance of lubrication, anti-volatilization, anti-crystallization and surface modification under extreme working conditions such as ultra-high temperature, high speed and heavy load.

[0042] In some alternative approaches, to further improve the compatibility of liquid metal lubricants with aero-engine bearing materials and suppress potential harmful chemical reactions between them, this disclosure provides a high-entropy alloy transition layer on the surfaces of the inner ring 111 and outer ring 112 of the bearing. It should be understood that the materials of the inner ring 111 and outer ring 112 are nickel-based superalloys, such as Inconel 718 or GH4169. This high-entropy alloy transition layer, through advanced surface engineering techniques such as laser cladding, magnetron sputtering, or hot isostatic diffusion bonding, forms a strong metallurgical bond with the working surface of the substrate raceway. It features no macroscopic interface defects, high bonding strength, and excellent high-temperature stability, ensuring long-term stable service under the harsh conditions of high temperature, high speed, and high load in aero-engine main bearings.

[0043] The aforementioned high-entropy alloy transition layer, on the one hand, leverages the excellent high-temperature hardness, wear resistance, and chemical stability of high-entropy alloys to enhance the wear resistance of the contact surfaces between the bearing inner ring 111, the bearing outer ring 112, and the liquid metal, adapting to the ultra-high temperature and high-load conditions of aero-engine main bearings and extending the service life of bearing components. On the other hand, it effectively prevents direct contact between the bearing matrix material and the liquid metal lubricant 120, forming a double protection with the modification effect of rare earth elements, further avoiding harmful chemical reactions between the liquid metal and the bearing matrix. Simultaneously, the surface interface characteristics of the high-entropy alloy transition layer improve the wettability of the liquid metal lubricant on the raceway surface, making it easier for the lubricant to form a continuous and uniform lubricating film, optimizing the lubrication effect. Furthermore, this transition layer reduces the adsorption residue of liquid metal lubricant on the bearing surface, and combined with the reflux effect of the cage's gradient pore structure, further reduces lubricant leakage and loss, ensuring the long-term stable operation of the lubrication system.

[0044] In some examples, the aforementioned high-entropy alloy transition layer is an alloy composed of five or more main metals mixed in near-equal atomic ratios or equal atomic ratios. Its unique high-entropy effect endows it with excellent mechanical properties, corrosion resistance, high-temperature resistance, and radiation resistance. The structural stability and performance synergy brought about by the high-entropy effect allow the transition layer to maintain structural integrity under ultra-high temperature, high load, and high-speed conditions in aero-engine main bearings. This directly improves the wear and erosion resistance of the raceway working surface, extending the service life of the bearing assembly, and also serves as a chemically inert isolation barrier, completely preventing direct contact between the bearing substrate and the liquid metal lubricant.

[0045] For example, the materials of the aforementioned high-entropy alloy transition layer include cobalt, chromium, iron, nickel, and molybdenum, that is, the material system of the aforementioned high-entropy alloy transition layer is a CoCrFeNiMo pentagonal system, with the atomic percentage content of molybdenum being 3 at.%~5 at.%, and the remaining metals being in near-equal atomic ratios or equal atomic ratios. This formulation scheme allows the alloy to retain the inherent advantages of the high-entropy system, and through the appropriate introduction of molybdenum, it can solid-solution strengthen the high-entropy alloy matrix, improving its hardness and strength at high temperatures. At the same time, molybdenum has a strong chemical affinity for free gallium ions in liquid metal, and can effectively capture these ions, forming a stable and dense passivation film on the surface of the bearing rings. This passivation film can prevent the liquid metal from further eroding the bearing matrix and prevent the formation of brittle intermetallic compounds, thereby significantly improving the corrosion resistance and long-term service reliability of the bearing. This design of setting a high-entropy alloy transition layer on the surface of the bearing inner ring 111 and the bearing outer ring 112 forms a high-performance buffer layer, effectively solving the compatibility problem between liquid metal and nickel-based superalloys.

[0046] In some examples, the thickness of the aforementioned high-entropy alloy transition layer is 0.8 mm to 1.2 mm. This thickness range is designed to balance structural strength, protective effect, and overall bearing compatibility. It ensures that the transition layer has sufficient thickness to resist frictional erosion and liquid metal corrosion under ultra-high temperature and high load conditions of aero-engine main bearings, avoiding protection failure and premature wear due to excessive thickness. At the same time, it avoids excessive thickness causing a surge in internal stress in the transition layer, effectively preventing structural failures such as interlayer peeling and cracking under high temperature conditions. It also adapts to the working surface accuracy requirements of the bearing raceway and does not affect the rotational fit accuracy of the bearing assembly.

[0047] like Figure 1 As shown, the bearing assembly 110 of this embodiment further includes a sealing structure 115. The sealing structure 115 includes a first seal 1151 connected to the outer ring 112 of the bearing and a second seal 1152 connected to the inner ring 111 of the bearing. The first seal 1151 and the second seal 1152 are disposed opposite to each other, and a tortuous sealing channel is formed between the first seal 1151 and the second seal 1152 to prevent leakage of liquid metal lubricant.

[0048] It should be noted that the above-mentioned sealing structure 115 is a labyrinth seal structure. The first seal 1151 and the second seal 1152 are arranged opposite to each other. The first seal 1151 is fixed to the outside of the bearing outer ring, and the second seal 1152 is fixed to the inside of the bearing inner ring, forming a tortuous sealing channel with multiple bends between them. This sealing path can effectively increase the flow resistance of liquid metal lubricant leakage to the outside, thereby achieving effective sealing and blocking of lubricant under high-speed rotation and temperature change conditions, preventing its leakage and contamination of other engine components.

[0049] Based on this, the sealing structure and the gradient pore structure of the cage 114 form a leak-proof synergistic system. The capillary pump self-pumping function of the cage actively pumps the lubricant thrown to the outside by centrifugal force back to the inner core lubrication area, reducing the migration of lubricant to the sealing area from the source. Meanwhile, the tortuous sealing channel forms the final barrier for the small amount of lubricant that escapes to the sealing area, greatly reducing the leakage loss of liquid metal lubricant.

[0050] In addition, the sealing surfaces of the first seal 1151 and the second seal 1152 are made of high-temperature wear-resistant materials with excellent compatibility with liquid metal lubricants. Under the high temperature and high speed rotation conditions of the main bearing of the aero-engine, the sealing surface can maintain the fitting accuracy and structural stability, and avoid sealing failure due to wear and deformation of the sealing surface.

[0051] Traditional labyrinth seals typically consist of a series of sealing teeth fixed to a rotating shaft and corresponding structures on a bearing housing, increasing leakage resistance by forming a tortuous flow path. However, this fixed-gap seal structure has limited effectiveness when dealing with liquid metals, especially at high temperatures, where the gap may widen due to thermal expansion of the material, leading to increased leakage.

[0052] Based on this Figure 3a A partial view of the sealing structure provided in an exemplary embodiment of this disclosure at room temperature is shown. Figure 3b A partial view of the sealing structure provided in an exemplary embodiment of this disclosure at a high temperature is shown. Figure 3a and Figure 3b As shown, in this embodiment of the present disclosure, sealing teeth protruding towards the second sealing member 1152 are formed on the first sealing member 1151, and a shape memory alloy element 1153 (SMA) is embedded in the top of the sealing teeth. This shape memory alloy element 1153 is a smart material with a special memory effect, capable of recovering to a preset shape at a specific temperature, preferably a nickel-titanium alloy or a copper-based shape memory alloy. The high-temperature state refers to the operating environment temperature of the sealing structure 115 reaching or exceeding the phase transition temperature of the shape memory alloy element.

[0053] In some examples, the phase transformation temperature of the aforementioned shape memory alloy element 1153 is 280℃~320℃, preferably 300℃. During engine startup and operation, as the temperature of the bearing and liquid metal lubricant rises, once the ambient temperature exceeds the phase transformation point of the alloy (e.g., 300℃), the shape memory alloy element embedded in the top of the sealing tooth is activated, undergoing a reversible martensitic-austenitic phase transformation, and generating active deformation based on its preset memory shape. This deformation can push the sealing tooth to move towards the relatively stationary component, thereby achieving adaptive adjustment of the sealing gap from the room temperature design value (e.g., 0.2mm) to the high temperature working gap (e.g., 0.05mm). This active, temperature-responsive gap control mechanism makes the tightness of the sealing structure increase synchronously with the increase of the working temperature, thereby effectively suppressing the risk of leakage caused by the decrease in viscosity and increase in fluidity of liquid metal under high temperature conditions.

[0054] In some examples, the liquid metal lubrication system of this disclosure embodiment further includes a resistance sensor 130, an ultrasonic sensor 140, and a temperature sensor 150. The electrodes of the resistance sensor 130 are disposed on the inner ring 111 and / or the outer ring 112 of the bearing to monitor the resistance value of the liquid metal lubricant 120. The probe of the ultrasonic sensor 140 is disposed radially outside the outer ring 112 of the bearing or on the bearing housing to emit ultrasonic waves into the raceway and receive reflected signals to detect the backflow state of the liquid metal lubricant driven by the gradient porosity structure. The temperature sensor 150 is disposed on the inner ring 111, the outer ring 112 of the bearing, or the cage to monitor the temperature at at least one location of the bearing assembly 110.

[0055] Specifically, the aforementioned resistance sensor utilizes the excellent conductivity of liquid metal to place electrodes on the inner and outer rings of the bearing to monitor the resistance value of the lubricant in real time. When the lubricating film is intact and of uniform thickness, the resistance value is relatively stable. Once the lubricating film ruptures, metal contacts occur, or impurities in the lubricant increase, the resistance value will change abruptly. The ultrasonic sensor, by installing miniature transmitting and receiving probes on the bearing housing, emits ultrasonic waves into the bearing and analyzes the amplitude, phase, and propagation time of the reflected waves. It can non-invasively detect defects, cracks, and the thickness and integrity of the lubricating film inside the bearing. For example, when the lubricating film thins or disappears, the amplitude of the ultrasonic reflected wave will increase significantly. The temperature sensor arranges miniature thermocouples or fiber optic temperature sensors in key parts such as the bearing rings, rolling elements, and cage to monitor the temperature distribution and change trend of each component in real time. An abnormal increase in local temperature is often a direct sign of lubrication failure or abnormal wear. The three types of sensors work together to achieve comprehensive monitoring of the lubrication system status.

[0056] In some examples, the resistance sensor 130, ultrasonic sensor 140, and temperature sensor 150 described above can be integrated into a compact module. The system can simultaneously acquire information about the electrical properties of the lubricant, the integrity of the lubricating film, and the thermal state of the system, providing a rich and reliable data foundation for subsequent diagnosis and early warning.

[0057] In one feasible way Figure 4 A flowchart illustrating a lubrication condition monitoring method for a liquid metal lubrication system provided in an exemplary embodiment of this disclosure is shown. Figure 4 As shown in the embodiments of this disclosure, the lubrication status monitoring method for a liquid metal lubrication system includes: S401: Acquire the resistance signal of the liquid metal lubricant and the ultrasonic signal inside the bearing assembly.

[0058] Specifically, resistance sensors located on the working surfaces of the raceways of the inner and / or outer rings of the bearing collect the resistance signal of the liquid metal lubricant in real time via electrodes immersed in the lubricant. This resistance value is sensitive to changes in lubricant composition, contaminant content, and liquid film thickness. Simultaneously, a miniature ultrasonic probe mounted on the bearing housing transmits ultrasonic waves into the bearing assembly and receives ultrasonic pulse or continuous wave signals propagating inside the bearing. This signal characterizes abnormal conditions such as lubricant deficiency, bubble formation, particulate contamination, or metal fatigue microcracks, thus completing the acquisition of the raw ultrasonic detection signal.

[0059] In some examples, the two signals can be synchronized in real time during the acquisition process, preserving the temporal correlation characteristics of the signals. At the same time, basic filtering and noise reduction processing is performed to eliminate signal noise caused by electromagnetic interference and structural vibration, resulting in effective resistance and ultrasonic signals that can be used for subsequent analysis, providing an accurate raw data foundation for multi-parameter fusion judgment.

[0060] S402: Determine whether the current change in the resistance signal exceeds a first threshold. It should be understood that this first threshold is a reference value preset based on the initial state of the liquid metal lubricant and the allowable range of performance changes, for example, the rate of change of resistivity relative to the initial reference value exceeding 10%.

[0061] Specifically, the system first retrieves the baseline resistance value when the lubrication is in good condition and the lubrication film is intact and uniform. The real-time resistance signal acquired by S401 and processed by filtering and noise reduction is compared with the baseline value to calculate the relative percentage change in the resistance value. The relative percentage change is then compared with a preset first threshold (10%) to determine whether the current change in the resistance signal exceeds the first threshold.

[0062] If the calculated percentage of relative change does not exceed the first threshold, the resistance signal of the current liquid metal lubricant is determined to be in the normal range, and no abnormality is caused by lubricating film rupture, direct metal contact, or increased impurities. The process returns to S401 to continue signal acquisition and monitoring. If the percentage of relative change exceeds the first threshold, the resistance signal is determined to be abnormal, and the process proceeds to subsequent steps. The signals from other sensors are then combined for collaborative verification to avoid misjudgment caused by a single abnormal signal.

[0063] S403: Determine whether the current change in the ultrasonic signal exceeds a second threshold. It should be understood that this second threshold is a pre-set reference value based on the statistical distribution of the characteristic parameters of the ultrasonic signal under normal lubrication conditions of the bearing assembly and the allowable engineering fluctuation range. For example, this second threshold can be set when the ultrasonic echo amplitude changes by more than 20% relative to a reference value.

[0064] Specifically, the baseline value of the ultrasonic reflected wave amplitude under normal lubrication conditions is retrieved from the system's pre-stored data. The real-time ultrasonic signal amplitude after filtering and synchronization processing in step 401 is compared with this baseline value, and the relative percentage change in the ultrasonic echo amplitude is calculated. If the relative change does not exceed 20%, the ultrasonic signal is determined to be within the normal range. Even if the resistance signal was abnormal previously, the fault triggering condition is not met, and the process returns to S401 to re-acquire and monitor the signal. If the relative change exceeds 20%, the ultrasonic signal synchronization is determined to be abnormal, satisfying the joint judgment condition of the multi-parameter "AND" logic, and the process proceeds to the subsequent fault confirmation and early warning steps.

[0065] S404: When the current change in the resistance signal exceeds the first threshold and the current change in the ultrasonic signal exceeds the second threshold, a lubrication failure is determined in the liquid metal lubrication system and a warning signal is generated.

[0066] Since a simple change in resistance may be caused by electromagnetic interference, and a simple change in ultrasonic signal may be caused by structural vibration, the simultaneous occurrence of both highly suggests damage to the lubricating film and metal-to-metal contact. Therefore, in this embodiment, only when both conditions are met—that the relative change in resistance signal exceeds a preset first threshold of 10% and the relative change in ultrasonic reflected wave amplitude exceeds a preset second threshold of 20%—are interference factors such as single sensor noise, electromagnetic interference, and structural vibration excluded, and the system is determined to be a genuine lubrication fault, such as lubricating film rupture or direct metal-to-metal contact, rather than a false anomaly signal. Upon confirmation of a lubrication fault, the system immediately generates a corresponding warning signal. The warning signal may include information such as the fault type and the time of occurrence, and can be used for local audible and visual alerts or uploaded to the engine integrated control system, providing a basis for subsequent fault handling and operating condition control. This effectively improves the accuracy and reliability of lubrication system fault diagnosis and avoids false warnings interfering with normal system operation. This dual-parameter collaborative judgment mechanism significantly improves the accuracy and reliability of fault diagnosis, reduces the risk of false alarms or missed alarms from a single signal, and provides effective condition monitoring assurance for the safe operation of aero-engine bearings under extreme conditions.

[0067] To more clearly illustrate the monitoring methods of this disclosure, Figure 5 A detailed flowchart of a lubrication condition monitoring method for a liquid metal lubrication system provided in an exemplary embodiment of this disclosure is shown, such as... Figure 5 As shown, the monitoring method includes: First, the system starts up and enters monitoring mode. After the system is powered on, it automatically enters real-time monitoring mode, and the resistance sensor 130, ultrasonic sensor 140, and temperature sensor 150 are simultaneously activated to prepare for data acquisition.

[0068] Then, real-time data from multiple sensors are acquired. These sensors include at least a resistance sensor for measuring the liquid metal lubricant, an ultrasonic sensor for measuring the internal structure of the bearing assembly, and a temperature sensor.

[0069] Next, the real-time data is preprocessed. Preprocessing includes filtering, denoising, and normalizing the acquired raw resistance, ultrasonic, and temperature signals: low-pass filtering is used to eliminate electromagnetic interference and high-frequency noise caused by structural vibration; normalization is used to unify sensor signals of different magnitudes into the same data range, improving the accuracy of subsequent feature extraction and obtaining high-quality, effective data.

[0070] Subsequently, based on the initial normal operation phase of the liquid metal lubrication system, signal baselines for each sensor are established, and the signal baselines are updated based on changes in the operating conditions of the liquid metal lubrication system.

[0071] Specifically, in the initial stage of normal system operation (when the lubricating film is intact and uniform and there are no faults), the system continuously collects sensor data, learns and establishes normal baseline values ​​for each signal, including the resistance baseline value R0, the ultrasonic reflected wave amplitude baseline value A0, and the temperature baseline value T0. In subsequent operation, the system periodically updates the baseline values ​​dynamically according to changes in engine operating conditions (such as speed and load adjustments) and the normal performance degradation law of the equipment, ensuring that the baseline values ​​always match the actual normal operating conditions and avoiding misjudgments caused by baseline drift.

[0072] Then, based on the currently acquired sensor data and the corresponding signal baseline, the current change in each sensor signal is calculated. This current change includes the rate of change in resistance of the signal acquired by the resistance sensor and the rate of change in the amplitude of the ultrasonic reflected wave of the signal acquired by the ultrasonic sensor.

[0073] The current changes in each sensor signal specifically include the resistance change rate ΔR / R0 (ΔR is the difference between the current resistance value and the baseline resistance value R0), the ultrasonic reflected wave amplitude change rate ΔA / A0 (ΔA is the difference between the current ultrasonic amplitude and the baseline amplitude value A0), and the deviation ΔT between the current temperature value and the temperature baseline value T0, which provides a quantitative basis for subsequent judgment.

[0074] Based on this, it is determined whether the resistance change rate is greater than a first preset threshold. If the resistance change rate ΔR / R0 ≤ the first threshold, the resistance signal is determined to be normal, and the process returns to S502 to continue the cyclic acquisition and monitoring; if the resistance change rate ΔR / R0 > the first threshold, the resistance signal is determined to be abnormal, and the process proceeds to the next step for multi-parameter collaborative verification.

[0075] If the aforementioned resistance change rate is greater than the first preset threshold, then it is further determined whether the change rate of the ultrasonic reflected wave amplitude is greater than the second preset threshold. The second preset threshold is 20%. If the change rate of the ultrasonic reflected wave amplitude ΔA / A0 ≤ the second threshold, it is determined to be a single signal interference (such as structural vibration), excluding a real lubrication fault, and returning to S502 to re-acquire and monitor data; if the change rate of the ultrasonic reflected wave amplitude ΔA / A0 > the second threshold, it is determined that the ultrasonic signal synchronization is abnormal, satisfying the multi-parameter AND logic judgment condition, and proceeding to S508.

[0076] If the rate of change of the reflected ultrasonic wave amplitude exceeds the second preset threshold, a lubrication failure is confirmed in the liquid metal lubrication system, and a warning signal is generated. When the system confirms that both ΔR / R0 > the first threshold (10%) and ΔA / A0 > the second threshold (20%) are met, false anomalies such as single sensor noise and external interference are eliminated, accurately determining a lubrication failure in the liquid metal lubrication system (e.g., lubricating film rupture, direct metal-to-metal contact, excessive lubricant impurities). At this time, the system automatically records data such as the time of the failure, the rate of change of resistance, the rate of change of ultrasonic amplitude, and the current temperature deviation, and immediately generates a warning signal. This warning signal can be displayed in real time via a local audio-visual module and simultaneously uploaded to the engine's full-authority digital electronic control system or the onboard health management system, providing accurate data support for fault handling.

[0077] The system stores the aforementioned monitoring data associated with lubrication failures and sends this data to an external system. The system automatically filters and stores all monitoring data directly related to the current lubrication failure, including raw data collected within a preset time period before and after the failure, pre-processed valid data, characteristic parameters (ΔR / R0, ΔA / A0), failure judgment logic results, and early warning trigger records. All data is stored in non-volatile memory to ensure data integrity after power failure. Simultaneously, the system sends the aforementioned associated monitoring data to an external system in real time via a standardized data interface. This external system includes an airborne health management system, an engine full authority digital electronic control system (FADEC), and a ground maintenance center. Data is sent to the airborne external system for real-time failure handling and control, and to the ground maintenance center for subsequent failure tracing, mechanism analysis, and maintenance plan optimization, comprehensively improving the system's failure handling efficiency and maintainability.

[0078] Finally, return and continue monitoring.

[0079] After the warning is issued, the system performs subsequent operations according to the preset fault level judgment rules: if the temperature deviation and the magnitude of the fault parameter change are judged to be a minor fault (such as a brief fluctuation of the lubricating film), it returns to S502 to continue continuous cyclic monitoring and track the fault development trend in real time; if it is judged to be a serious fault (such as complete rupture of the lubricating film or continuous metal friction), the system is triggered to enter the safety mode, such as adjusting the engine operating conditions through the digital electronic control system (reducing speed and load) and starting the backup lubrication mechanism, to prevent the fault from expanding and causing damage to the bearing components. At the same time, the sensor continues to monitor until the fault is eliminated or the system is shut down for maintenance, forming a closed-loop control.

[0080] Example Preparation and Injection of Liquid Metal Lubricant: According to the formula required by this disclosure, the raw materials of each component are first accurately weighed under an argon protective atmosphere. High-purity gallium, indium, and zinc metals are placed in a graphite crucible and installed in an induction melting furnace. The furnace temperature is raised to 450°C, and after the metals are completely melted, thorough stirring is performed. Subsequently, pre-prepared nano-sized yttrium powder is slowly added to the molten alloy, and an ultrasonic dispersion device is immediately started and treated at a frequency of 20 kHz for 30 minutes to ensure uniform dispersion of nanoparticles. After preparation, the liquid metal is cooled to room temperature to obtain a solid lubricant ingot. Before bearing assembly, the ingot is reheated to a molten state and injected into the assembled bearing in a vacuum environment using a dedicated oil injection device to ensure that all lubrication gaps are fully filled.

[0081] Bearing assembly and commissioning: The bearing assembly is carried out in a clean environment with a cleanliness level of not less than ISO 5. First, the bearing inner ring, bearing outer ring, and rolling elements with a CoCrFeNiMo high-entropy alloy transition layer on their surfaces are pre-assembled. Then, the cage, integrally formed using selective laser melting technology and featuring a gradient porosity structure, is precisely installed. Ni-Ti alloy elements with shape memory treatment are pre-set and fixed within the tooth gaps of the labyrinth seal structure. After all mechanical components are assembled, dynamic balancing tests and preload adjustments are performed to ensure that the bearing's rotational accuracy and static and dynamic stiffness meet design requirements. Finally, the monitoring module integrating resistance, ultrasonic, and temperature sensors is installed in the preset position, and preliminary electrical connections and functional tests are completed.

[0082] Calibration and Operation of the Intelligent Monitoring Module: Before the bearing system is first operated, the intelligent monitoring module must be calibrated. The assembled bearing is installed on a dedicated test bench and run under simulated normal operating conditions for a preset duration (e.g., 2 hours). During this period, the monitoring system automatically collects and records signals from resistance, ultrasonic, and temperature sensors to establish normal operating baselines for each parameter. After calibration, the system enters formal monitoring mode. Within the entire operating envelope of the engine, the monitoring module continuously collects data at high frequency and executes multi-parameter fusion diagnostic algorithms in real time. Once a fault characteristic meeting a preset warning threshold is detected, the system immediately sends a warning signal to the engine's full authority digital electronic controller via the CAN bus or ARINC429 bus, while simultaneously recording a fault log containing timestamps, sensor data, and processing results, providing data support for subsequent condition assessment and maintenance decisions.

[0083] The above description is merely an illustration of some embodiments of this disclosure and the technical principles employed. Those skilled in the art should understand that the scope of this disclosure is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the above-described concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features disclosed in this disclosure that have similar functions.

[0084] While specific embodiments of this disclosure have been described in detail by way of example, those skilled in the art should understand that the examples are for illustrative purposes only and not intended to limit the scope of this disclosure. Those skilled in the art should understand that modifications can be made to the above embodiments without departing from the scope and spirit of this disclosure. The scope of this disclosure is defined by the appended claims.

Claims

1. A liquid metal lubrication system, characterized in that, include: A bearing assembly and a liquid metal lubricant, wherein the liquid metal lubricant fills the gaps in the bearing assembly and the liquid metal lubricant contains rare earth elements; The bearing assembly includes an inner bearing ring, an outer bearing ring, multiple rolling elements, and a cage. The multiple rolling elements are located within a raceway formed by the inner and outer bearing rings. The cage is disposed within the raceway to separate and guide the rolling elements. The cage has a gradient porosity structure inside, with the porosity continuously decreasing along the direction from the inner to the outer bearing ring. The gradient porosity structure is used to drive the liquid metal lubricant to flow back from the outer region with low porosity to the inner region with high porosity in the centrifugal force field generated by the rotation of the bearing assembly.

2. The liquid metal lubrication system according to claim 1, characterized in that, The liquid metal lubricant further includes gallium, indium, and zinc. Based on a mass percentage of 100% of the liquid metal lubricant, the mass percentage of gallium is 65% to 70%, the mass percentage of indium is 20% to 25%, the mass percentage of zinc is 9.5% to 9.9%, and the mass percentage of rare earth elements is 0.1% to 0.5%. The rare earth elements are uniformly dispersed in the liquid metal lubricant in the form of nanoparticles.

3. The liquid metal lubrication system according to claim 1, characterized in that, The surfaces of the inner and outer rings of the bearing are provided with a high-entropy alloy transition layer.

4. The liquid metal lubrication system according to claim 3, characterized in that, The high-entropy alloy transition layer is made of cobalt, chromium, iron, nickel and molybdenum, wherein the atomic percentage content of molybdenum is 3 at.% to 5 at.% and the thickness of the high-entropy alloy transition layer is 0.8 mm to 1.2 mm.

5. The liquid metal lubrication system according to claim 1, characterized in that, The bearing assembly further includes a sealing structure comprising a first seal connected to the outer ring of the bearing and a second seal connected to the inner ring of the bearing. The first seal and the second seal are disposed opposite to each other, and a tortuous sealing channel is formed between the first seal and the second seal to prevent leakage of the liquid metal lubricant.

6. The liquid metal lubrication system according to claim 5, characterized in that, The first seal has sealing teeth that protrude toward the second seal, and the top of the sealing teeth is embedded with a shape memory alloy element.

7. The liquid metal lubrication system according to claim 6, characterized in that, The phase transition temperature of the shape memory alloy element is 280℃~320℃.

8. The liquid metal lubrication system according to claim 1, characterized in that, It also includes resistance sensors, ultrasonic sensors, and temperature sensors; The electrodes of the resistance sensor are disposed on the inner ring and / or outer ring of the bearing, for monitoring the resistance value of the liquid metal lubricant; the probe of the ultrasonic sensor is disposed on the radially outer side of the outer ring of the bearing or on the bearing housing, for emitting ultrasonic waves into the raceway and receiving reflected signals to detect the backflow state of the liquid metal lubricant driven by the gradient porosity structure; the temperature sensor is disposed on the inner ring, outer ring of the bearing, or the cage, for monitoring the temperature at at least one location of the bearing assembly.

9. A method for monitoring the lubrication status of a liquid metal lubrication system, applied to the liquid metal lubrication system according to any one of claims 1 to 8, characterized in that, include: Obtain the resistance signal of the liquid metal lubricant and the ultrasonic signal inside the bearing assembly; Determine whether the current change in the resistance signal exceeds a first threshold. Determine whether the current change in the ultrasonic signal exceeds a second threshold; When the current change in the resistance signal exceeds the first threshold and the current change in the ultrasonic signal exceeds the second threshold, a lubrication failure is determined in the liquid metal lubrication system and a warning signal is generated.

10. A mechanical device, characterized in that, The liquid metal lubrication system as described in any one of claims 1 to 8 is employed.

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