Study on the cooling performance of aviation gear oil with nanodiamonds as additives

Study on the cooling performance of aviation gear oil with nanodiamonds as additives | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Study on the cooling performance of aviation gear oil with nanodiamonds as additives Lei Wei, Feihui Yang, Pan Xie, Jiajun He, Yongbin Cao, Yixuan Li, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5653720/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract In order to enhance the service performance of aviation gear oil. This work studied the effect on the cooling performance of aviation gear oil with nanodiamonds (NDs) as additives. Different contents (0.05 wt.%, 0.10 wt.%, 0.20 wt.%, 0.30 wt.%, 0.60 wt.%) of NDs were added into aviation gear oil, and different dispersants were used to disperse the NDs, which were compounded into highly dispersible NDs gear oils. Temperature rise tested by thermostatic water bath device. Molecular modeling to simulate the microscopic mechanism of nanodiamonds interaction with gear oil. The results showed that nanodiamonds could effectively enhance the cooling performance of aviation gear oil. The cooling performance was better with the increase of NDs content, which tended to stabilize at 0.6 wt.%. It was improved by 22.87% relative to the control. The longer the dispersion time, the worse the cooling performance of NDs gear oil. The interfacial bonding between the NDs molecules and the oil molecules enhanced the cooling rate of the gear oil. This study revealed the intrinsic mechanism of nanodiamonds as additives to enhance the cooling performance of gear oil. It provided theoretical guidance for the application of aviation gear oil and provided guarantee for the smooth operation of aviation equipment. aviation gear oil nanodiamonds cooling performance molecular dynamics simulation Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 1. Introduction As a key component of the aviation transmission system, the lubrication status of gears directly affects the operational safety and performance stability of the aircraft [1]. Therefore, the development of high-performance, long-life aviation gear lubricating oil has become an important issue in the current aviation lubrication technology research [2]. During aircraft operation, aviation gears need to operate at high speeds, high temperatures, high pressures and other extreme conditions, which requires lubricating oil to have excellent extreme pressure, anti-wear, thermal stability and oxidation resistance [3–5]. The cooling performance of the lubricant is not only related to the normal operation of the equipment, but also closely related to the service life and efficiency of the equipment [6–7]. The cooling performance of different types and formulations of lubricants may vary significantly [8–10]. In recent years, the rapid development of nanotechnology has provided new solutions for aviation gear lubrication, and nano-lubricants have received widespread attention in the aviation field due to their unique anti-wear and friction reduction properties [11–14]. Since Nanodiamonds have good thermal conductivity [15–17] and lubricity [18–20], so adding them to gear oil in the right amount can help improve the overall thermal conductivity of gear oil. Pico D F M et al [21] used POE synthetic refrigeration oil with two different mass fractions of synthetic diamond nanoparticles as a nano-lubricant in vapor compression refrigeration systems and showed that 0.1% and 0.5% nanodiamonds reduced friction and wear by about 4% and about 30%, respectively, and improved the coefficient of performance and cooling capacity. In addition, nanodiamond as an all-carbon nontoxic additive, is highly environmentally friendly and meets the environmental requirements for the development of aviation gear lubricants [22–25]. However, despite the great potential of nanodiamond in aviation gear lubrication, the cooling mechanism of nanodiamond in gear oils is not fully understood. In this work, a temperature rise test setup was constructed with a thermostatic water bath to test the temperature rise of different variables of gear oil. To investigate the effects of nanodiamond content, gear oil type, dispersant type and other factors on the cooling performance of gear oil. Molecular dynamics simulations by constructing microscopic molecular models of gear oil. A microscopic investigation to reveal the mechanism of nanodiamond increased cooling performance on gear oil. The aim of this study was investigated in depth the effect of nanodiamonds as additives on the cooling performance of aviation gear oil, demonstrating the intrinsic mechanism of the nanodiamonds enhanced cooling performance of gear oil. It provided theoretical basis for the application of nanodiamond in aviation gear oil and promoted the further development of aviation gear lubrication technology. 2 Experimental details 2.1 Materials and equipment Two synthetic gear oils of different viscosity grades and one mineral gear oil were used as solvents (relevant information is shown in Table 1 ). Nanodiamonds of 10–30 nm particle size was used as an additive (Zhen Drill Abrasives Co., Ltd.). Table 1 Test gear oil Gear oil brands and models Types of gear oil viscosity grade Shell 555 synthetic oil 100 Turbo Oil 2197 synthetic oil 27 Mobil 600XP mineral oil 100 The test equipment included single-well digital display constant temperature water bath, WST digital thermometer, precision electronic balance, electric stirrer and ultrasonic cleaner. 2.2 Test design of NDs gear oil temperature rise First, different contents (0.05 wt.%, 0.10 wt.%, 0.20 wt.%, 0.30 wt.%, 0.60 wt.%) of nanodiamonds were added to 50 ml of aviation gear oil (Test Group 1: Shell 555; Test Group 2: Turbo Oil 2197; Test Group 3: Mobil 600XP). Compounded into NDs gear oil. Mechanical stirring was carried out for 30 minutes by means of an electric stirrer to ensure that the NDs were effectively dispersed in the gear oil. Then 1 wt.% of the dispersant was added to the NDs gear oil. Dispersion was carried out by ultrasonication for 1 h and again by mechanical mixing for 30 min. Obtained NDs gear oil with different dispersion profiles. The NDs gear oil was transferred to a sealed test tube for storage. Construct a set of gear oil heating detection device using constant temperature water bath method. Simulate the high-temperature working conditions faced by gear oil in the actual working process. The experimental principle of the device is shown in Fig. 1 (b). Three groups of test gear oil after dispersant dispersion for 1 h and 96 h were selected as the test objects for temperature rise test. Gears, as key components in mechanical equipment, usually operate in complex environments with high temperatures. Therefore, a water bath temperature of 90°C is used as a thermostatic source to transfer heat to the gear oil, and the rate of heating of the gear oil from 25°C to 65°C is tested. 2.3 Molecular modeling of NDs gear oil (1) Molecular modeling of synthetic oil PAO (polyalphaolefin), as a synthetic base stock widely used in the field of gear oils, has a unique molecular structure and excellent performance characteristics that make it an important part of the development of industrial lubrication technology. The molecular structure consists mainly of relatively regular long-chain alkanes, as shown in Fig. 2 . The synthetic gear oil model containing 12 PAO monomer models was constructed by constructing an amorphous polymer, and the volume size of this amorphous cell model was 24.02 nm × 24.02 nm × 20.42 nm, as shown in Figure. 3. (2) Molecular modeling of mineral oil Mineral oil as a traditional lubricant base stock. Its composition is complex, mainly including chain alkanes, cycloalkanes and aromatic hydrocarbons and other hydrocarbons. In order to study more deeply the differences in microstructure and properties between mineral oil and synthetic oil, a mineral oil model based on cycloalkyl mineral oil components was constructed. Referring to the mass ratio of mineral oil components tested in the relevant literature [26]. By calculating the relative molecular mass of each component, the molar ratios of the components of the naphthenic mineral oil were obtained as shown in Table 2 . Table 2 Component of naphthenic mineral oil Chain alkane Total cycloalkanes Aromatic hydrocarbons One ring Two rings Three rings Four rings Molecular formula C 12 H 26 C 14 H 28 C 13 H 24 C 16 H 28 C 16 H 26 C 19 H 30 Mass fraction % 11.67% 17.28% 24.07% 24.69% 14.81% 7.48% Using the method proposed by Theodorou et al [18] for the preparation of amorphous polymers. Six standard cycloalkyl mineral oil compositions were prepared in molar ratios to obtain standard amorphous mineral oil crystals as shown in Fig. 4 . In order to make the simulation results more accurate, the relative molecular mass and cell volume of the mineral oil molecular model were further set up. Making it consistent with the synthetic oil model. (3) Molecular modeling of nanodiamonds The nanodiamond cell model and molecular model are shown in Figure. 5, and the volume size of the molecular model is set to 0.2 nm. Its molecular structure consists of carbon atoms connected in the form of sp3 hybridization, and each carbon atom is surrounded by four neighboring carbon atoms, forming a three-dimensional mesh structure. (4) Molecular modeling of NDs gear oil Three of the five critical groups of nanodiamond content (0.1 wt.%, 0.3 wt.% and 0.6 wt.%) mentioned in the previous section were selected as the focus of the study. The nanodiamond molecular model was populated into the gear oil model according to three molar mass ratios. A synthetic oil model and a mineral oil model containing nanodiamond additives were constructed, respectively, as shown in Figs. 6 and 7 . By comparing the structural and performance differences between these two models at the molecular level, an in-depth understanding of the interaction mechanism between nanodiamonds and different types of gear oils was obtained. Two molecular dynamics simulation temperatures, 298 K and 363 K, were set according to the test temperatures in the previous thermostatic water bath tests. four sets of gear oil models were explored for the temperature variation laws at room temperature and test temperatures, respectively. The simulation duration was set to 200 ps. Given that the COMPASS force field has been shown to accurately simulate the motion of small molecules in silica-alumina media [28–29], it was chosen for structure optimization and molecular simulation. The Verlet velocity algorithm was used to solve Newton's equations to obtain the positions and kinetic energies of all atoms in the model at each time point. An atom-based approach was used to calculate the van der Waals forces. Ewald summation method is used to calculate the electrostatic forces. 3.Results and analysis 3.1 Study of NDs gear oil temperature rise rate The temperature rise rate of the three sets of test gear oil after dispersion for 1 h from 25°C to 65°C in a 90°C thermostatic water bath was obtained by calculation, and the data is shown in Fig. 8 . Of the three groups of gear oil without nanodiamonds. The gear oil in test group 1 (Shell 555, synthetic, viscosity grade 100) exhibited the lowest rate of temperature rise at 0.188°C/s. The gear oil in test group 2 (Turbo Oil 2197, synthetic, viscosity grade 27) exhibited a slightly higher rate of temperature rise at 0.198°C/s than test group 1. The gear oil in test group 3 (Mobil 600XP, mineral oil, viscosity grade 100) showed the highest rate of temperature rise at 0.204°C/s. All of the gear oil with nanodiamonds were temperature rise lower than the gear oil without nanodiamonds. When nanodiamond content reached 0.06 wt%, the temperature rise rate of each test gear oil reached the lowest value and gradually stabilized. Different dispersants had different effects on the temperature rise rate of the gear oil. In test group 1, the silane coupling agent group had the most significant cooling effect. Its lowest temperature rise rate was 0.145°C/s, which was 22.87% lower relative to the control gear oil. In experimental group 2, the oleic acid group showed the most significant temperature cooling effect. Its lowest temperature rise rate was 0.163°C/s, which was 17.68% lower relative to the control gear oil. In test group 3, the silane coupling agent group had the most significant temperature cooling effect. Its lowest temperature rise rate was 0.145°C/s, which was 11.27% lower than that of the control gear oil group. Among all the test groups after 1 h of dispersion, the silane coupling agent group in test group 1 had the lowest temperature rise rate. The temperature rise rate data for the three sets of test gear oils after 96 h of dispersion from 25°C to 65°C in a 90°C thermostatic water bath is shown in Fig. 9 . Similar to the case of dispersion for 1 h, all test groups showed a decrease in the rate of temperature rise compared to the control group. When the nanodiamond content was at 0.6 wt.%, the test groups achieved the lowest temperature rise rate and gradually stabilized. Among the test 1 groups, the oleic acid group showed the most significant temperature cooling effect. Its lowest temperature rise rate was 0.165°C/s, which was 12.23% lower relative to the control gear oil. In test group 2, the oleic acid group has the most significant temperature cooling effect. The lowest temperature rise rate was 0.166°C/s, which was 16.16% lower than that of the control gear oil. In test group 3, the oleic acid group has the most significant temperature cooling effect. Its lowest temperature rise rate was 0.187°C/s, which was 8.33% lower than that of the control gear oil. In all test groups after 96 h of dispersion, the lowest temperature rise rate was in the oleic acid group, followed by the polyethylene glycol group, and the highest in the silane coupling agent group. As shown in Figs. 2 and 3 . In all test groups, the temperature rise rate of gear oil showed a decreasing trend with the addition of nanodiamonds. And with the further increase of NDs content, the temperature rise rate gradually decreased and stabilized. Nanodiamonds affect the cooling performance of synthetic oil significantly better than mineral oil. The best cooling effect of NDs synthetic oil was 2.03 times higher than NDs mineral oil. With the increase of dispersion time, the change in temperature rise rate after 96 h of dispersion was significantly reduced compared to the case of 1 h of dispersion. Among them, the oleic acid group showed the smallest change after 96 h of dispersion, the polyethylene glycol group was the second largest, and the silane coupling agent group showed the largest change. 3.2 Molecular dynamics simulation of NDs gear oil Structural optimization and annealing by COMPASS force field. Molecular dynamics simulations were performed. Deriving the temperature variation rule of four groups of test synthetic gear oil at different temperatures. As shown in Figure. 10. The average temperatures for each set of modeled reactions were calculated as shown in Table 3 . The temperature differences between synthetic oil with nanodiamonds and without nanodiamonds were also comparatively analyzed. At the simulated temperature of 298 K, with the extension of simulation time, the average temperatures of the four combined synthetic oil models showed significant differences. The average temperatures of the synthetic oil model were 188.95 K, 183.32 K, 179.56 K, and 187.55 K, respectively, in order of NDs content from lowest to highest. This result tentatively suggested that synthetic oil spiked with nanodiamonds exhibit lower average temperatures at lower temperatures. Implying nanodiamonds may had a positive effect on the cooling performance of gear oil. When the simulated temperature was increased to 363 K, the average temperatures of the synthetic oil model were 238.63 K, 218.73 K, 220.14 K, and 222.13 K, respectively. Compared to the results at 298 K, the overall temperature increased, and the synthetic oil with nanodiamonds still exhibited relatively low average temperatures. This further confirms the enhancement of the cooling performance of gear oil by nanodiamonds. In the two sets of molecular dynamics simulation results at different temperatures, the temperature of the synthetic oil reached the minimum in the range of 0.1 wt. % -0.3 wt. % of the NDs content. Table 3 Average temperatures of molecular model of test synthetic oil 0.0 wt.% NDs 0.1 wt.% NDs 0.3 wt.% NDs 0.6 wt.% NDs 298 K 188.95 K 183.32 K 179.56 K 187.55 K 363 K 238.63 K 218.73 K 220.14 K 222.13 K The molecular dynamics simulation of four groups of mineral gear oil model were carried out, and the temperature variation rules of four groups of test mineral gear oil at different temperature were derived as shown in Figure.11. The average temperatures of the four groups of mineral gear oil at different setting temperatures were calculated as shown in Table 4 . At 298 K, with the extension of simulation time, the average temperatures of the four groups of mineral oil model were 195.55 K, 185.44 K, 190.30 K, and 190.71 K, respectively. At 363 K, the average temperatures were 243.59 K, 221.33 K, 221.09 K and 227.69 K, respectively. In the four groups of mineral oil model, the average temperatures of mineral oil with nanodiamonds were lower than those without nanodiamonds, which can prove that nanodiamonds can effectively enhance the cooling performance of mineral gear oil. At the same time, the average temperatures of the four groups of mineral oil model under two temperature fields were higher than those of the synthetic oil model, which can indicate that the molecular structure of synthetic oil was more stable and thermally stable than mineral oil. Table 4 Average temperatures of molecular model of test mineral oil 0.0 wt.% NDs 0.1 wt.% NDs 0.3 wt.% NDs 0.6 wt.% NDs 298 K 195.55 K 185.44 K 190.30 K 190.71 K 363 K 243.59 K 221.33 K 221.09 K 227.69 K From a microscopic point of view, NDs act as additives in gear oil, and their microstructure provides a large amount of surface area to effectively adsorb and transfer heat. By filling microscopic defects and irregular surfaces in the oil, nanodiamonds are able to reduce localized hot spots in the oil and increase the heat conduction path, thus improving the thermal conductivity of the oil. At the same time, the interfacial interaction between nanodiamonds and oil molecules also plays a key role. The surface of the nanodiamonds is rich in functional groups, which can form hydrogen bonds, van der Waals forces and other interactions with the lubricant molecules, and improve the compatibility between the nanodiamonds and the oil. This interfacial interaction makes the nanodiamonds better dispersed in the fluid, and can effectively transfer heat and improve the thermal conductivity of the oil. 4.Conclusion In this study, the effects of nanodiamond content and dispersant type on the temperature rise rate of different types of aviation gear oil were investigated through gear oil temperature rise test. Combined with molecular dynamics simulation, the intrinsic mechanism of nanodiamond enhanced cooling performance of gear oil was investigated. The conclusions are as follows: (1) Nanodiamonds had a better effect in enhancing the cooling performance of gear oil. In the range of 0.05 wt. % -0.6 wt. %, the temperature rise rate of the NDs gear oil gradually decreased and leveled off with the increase of NDs content. (2) Nanodiamonds were more suitable for use as additives in synthetic oil. NDs synthetic oil had a 2.03 times greater cooling effect than NDs mineral oil. The effect of nanodiamonds on the cooling properties of gear oil decreased with the increase of dispersion time. (3) The interfacial binding effect between NDs molecules and oil molecules. It could effectively improve the compatibility between nanodiamonds and gear oil and promote the dispersion of nanodiamonds in oil. Declarations Author Contribution Dr. Wei: Conceptualization, Methodology, Validation, Project administration. Yang: Writing - Original Draft, Investigation. Xie: Resources. He: Visualization. Cao: Data Curation. Li: Formal analysis. Zhong: Visualization. Dr. Chen: Writing - Review & Editing. Acknowledgments The authors are grateful for the financial support from the National Natural Science Foundation of China (Grant No. 52105055), National Natural Science Foundation of China (Grant No. 52475056), Natural Science Foundation of Hunan Province, (Grant No.2023JJ30281), Open Fund Project of Key Laboratory of Hunan Province for Efficient Power System and Intelligent Manufacturing (Grant No. 2022KF05), Aid Program for Science and Technology Innovative Research Team in Higher Educational Institutions of Hunan Province(High Performance Manufacturing Processes and Service Performance Optimization). References Zhao J, Sheng W, Li Z, et al. Effect of lubricant selection on the wear characteristics of spur gear under oil-air mixed lubrication[J]. Tribology International, 2022, 167: 107382. Li L, Wang S, Zhang X, et al. Numerical Calculation Analysis and Characteristic Research on Windage Loss of Oil-Jet Lubricated Aviation Gear Pair[J]. International Journal of Aerospace Engineering,2022,2022. Jie Z, Min Y, Arndt J, et al. Characterising the effects of simultaneous water and gasoline dilution on lubricant performance [J]. Tribology International, 2023, 179 Urmilla B, Maitrayee S, J. I B, et al. Functionalized polyethylene on property enhancement of lubricating oil and their performance evaluation study [J]. Journal of Applied Polymer Science, 2022, 140 (4): Pratap A S, Kumar R D, Amit S. Influence of nano particles on the performance parameters of lube oil – a review [J]. Materials Research Express, 2021, 8 (10): Saidur R, Kazi S N, Hossain M S, et al. A review on the performance of nanoparticles suspended with refrigerants and lubricating oils in refrigeration systems[J]. Renewable and Sustainable Energy Reviews, 2011, 15(1): 310-323. Kobasko N I, Souza E C D, Canale L D C F, et al. Vegetable Oil Quenchants: Calculation and Comparison of The Cooling Properties of a Series of Vegetable Oils[J]. Strojniski Vestnik, 2010, 56(2). Muhammad J, Ning H, Wei Z, et al. Tribological behavior of WC-6Co against Ti–6Al–4V alloy under novel cryogenic ethanol-ester oil dry-ice hybrid lubri-cooling[J]. Tribology International,2021,156106812-. Pinheiro C T, Pais R F, Ferreira A G M, et al. Measurement and correlation of thermophysical properties of waste lubricant oil[J]. The Journal of Chemical Thermodynamics, 2018, 116: 137-146. Pereira O, Rodríguez A, Ayesta I, et al. A cryo lubri-coolant approach for finish milling of aeronautical hard-to-cut materials[J]. Int. J. of Mechatronics and Manufacturing Systems,2016,9(4):370-384. Duan Z, Wang S, Wang Z, et al. Tool wear mechanisms in cold plasma and nano-lubricant multi-energy field coupled micro-milling of Al-Li alloy[J]. Tribology International, 2024,192109337-. Ma L, Ma L, Ma X, et al. Tribological Properties and Lubrication Mechanisms of Water-Based Nanolubricants Containing TiO 2Nanoparticles during Micro Rolling of Titanium Foils[J]. Materials,2023, 17(1). Mu’taz A, Salloom A. The effect of nanolubrication on wear and friction resistance between sliding surfaces[J]. Industrial Lubrication and Tribology, 2023, 75(5): 526-535. Weiwei T, Yi W, Xuejun Z, et al. Graphitic carbon nitride quantum dots as novel and efficient friction-reduction and anti-wear additives for water-based lubrication[J]. Wear, 2023, 528-529. Tianhao A, Wutong F, Zhonglai R, et al.Simultaneous enhancement of mechanical performance and thermal conductivity for polyamide 10T by nanodiamond compositing[J].Journal of Applied Polymer Science,2021,139(19): Aleksei V, Sergey K, Alexander V, et al.Hardness and thermal conductivity of a composite based on aluminum modified with a hybrid material detonation nanodiamond/few-layer graphene[J].Fullerenes, Nanotubes and Carbon Nanostructures,2022,30(1):205-210. Chaoyu W, Junqi S, Zhi H, et al. Flexible silicone rubber/carbon fiber/nano-diamond composites with enhanced thermal conductivity via reducing the interface thermal resistance[J]. Journal of Polymer Engineering,2022,42(6):544-553. Shuqing C, Qi D, Yan G, et al. Study of Tribological Properties of Fullerenol and Nanodiamonds as Additives in Water-Based Lubricants for Amorphous Carbon (a-C) Coatings[J]. Nanomaterials,2021,12(1):139-139. Abdulhakeem J, Bibin J. Tribological performance of nanolubricants dispersed with graphene oxide and detonation nanodiamond[J]. Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology,2021,235(9):1937-1949. Ruoxuan H, Shinan H, Tianchi Z, et al. Characterization and tribology performance of polyaniline-coated nanodiamond lubricant additives[J]. Nanotechnology Reviews,2022,11(1):2190-2201. Pico D F M, da Silva L R R, Mendoza O S H, et al. Experimental study on thermal and tribological performance of diamond nanolubricants applied to a refrigeration system using R32[J]. International Journal of Heat and Mass Transfer, 2020, 152: 119493. Wenshuang H, Minjie W, Jianxin R, et al. Effect of functionalized nanodiamond on properties of polylactic acid eco-friendly composite films[J]. Diamond & Related Materials,2023,133. Mostovoy A, Bekeshev A, Shcherbakov A, et al. Investigating the Structure and Properties of Epoxy Nanocomposites Containing Nanodiamonds Modified with Aminoacetic Acid[J]. Polymers,2024,16(4). Torres‐Sanchez C, Balodimos N. Effective and Eco‐friendly Lubrication Protocol Using Nanodiamonds in a Dry Regime for Conveyor Systems in the Beverage Industry[J].Packaging Technology and Science,2017,30(5):209-218. Chun Z, Mufan A, Minjie W, et al. Effect of curcumin-modified nanodiamonds on properties of eco-friendly polylactic acid composite films[J]. Colloids and Surfaces A: Physicochemical and Engineering Aspects,2024,680. Liu F, Xu W. Characteristic comparison between paraf-fine-base and naphthene-base transformer oils[J]. Transformer, 2004, 41(7): 27-30. Theodorou Doros N., Suter Ulrich W. Detailed molecular structure of a vinyl polymer glass[J]. Macromolecules, 1985, 18(7): 1467-1478. Li Y, Zhang X, Ye F, et al. Influence regularity of O2 on dielectric and decomposition properties of C4F7N-CO2-O2 gas mixture for MV equipment[J]. Hig h Voltage, 2020, 5(3): 256-263. Chen Z. Theory and Practice of Molecular Simulation[M]. Beijing: Chemical Industry Press, 2007: 6-18. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-5653720","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":391390503,"identity":"b57a93d1-3efe-4695-b15a-84806c9b82e1","order_by":0,"name":"Lei Wei","email":"","orcid":"","institution":"School of Mechanical Engineering, Hunan Institute of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Lei","middleName":"","lastName":"Wei","suffix":""},{"id":391390505,"identity":"0c700655-5099-4a37-851d-758d1919c6b4","order_by":1,"name":"Feihui Yang","email":"","orcid":"","institution":"School of Mechanical Engineering, Hunan Institute of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Feihui","middleName":"","lastName":"Yang","suffix":""},{"id":391390507,"identity":"5455e50e-4645-4c43-95ac-4d7c0f0eee92","order_by":2,"name":"Pan Xie","email":"","orcid":"","institution":"School of Mechanical Engineering, Hunan Institute of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Pan","middleName":"","lastName":"Xie","suffix":""},{"id":391390510,"identity":"b6acba44-859d-44a3-9f15-ba7de61691e8","order_by":3,"name":"Jiajun He","email":"","orcid":"","institution":"School of Mechanical Engineering, Hunan Institute of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Jiajun","middleName":"","lastName":"He","suffix":""},{"id":391390512,"identity":"ca483ef3-9876-4859-a7fc-a655833f417d","order_by":4,"name":"Yongbin Cao","email":"","orcid":"","institution":"School of Mechanical Engineering, Hunan Institute of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Yongbin","middleName":"","lastName":"Cao","suffix":""},{"id":391390513,"identity":"5ccadc41-9f92-488d-ae39-9e4c8f5b9b82","order_by":5,"name":"Yixuan Li","email":"","orcid":"","institution":"School of Mechanical Engineering, Hunan Institute of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Yixuan","middleName":"","lastName":"Li","suffix":""},{"id":391390514,"identity":"4d0d131a-f7ed-4021-bc3e-f0e68b925749","order_by":6,"name":"Yifeng Zhong","email":"","orcid":"","institution":"School of Mechanical Engineering, Hunan Institute of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Yifeng","middleName":"","lastName":"Zhong","suffix":""},{"id":391390515,"identity":"37ea9eaa-0c91-4779-8443-fc5362fca1ea","order_by":7,"name":"Song Chen","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA6ElEQVRIie2OsQrCMBRFUwSnaNeUgv5CpNBJ9FeeFHQJ6OimILi5R/wJQXBuCehSnAN2cXEXQeJmKrrGuAnmQPLu8A7vIuRw/CLkNX0d0mdKbZWAl8vwjUJl+dso/mq2O6lx0dkcF1l2V6hRl+BdR6YjxW4Q4fycbIsDCAwoCiRUQm5QKGFx6M1FEktGhS7WW0uoVrBRGd6Cu1YizmimAE0sFFYltbno6EBTXQzoJ4XIfhziXAApi+E+aS3z0yw0KT5PzoEai67PWXRR7Xazvk+yq0l505u+rurnTS0EhLpWWw6Hw/GfPADXdU4gODeJngAAAABJRU5ErkJggg==","orcid":"","institution":"School of Mechanical Engineering, Hunan Institute of Science and Technology","correspondingAuthor":true,"prefix":"","firstName":"Song","middleName":"","lastName":"Chen","suffix":""}],"badges":[],"createdAt":"2024-12-16 12:23:31","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5653720/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5653720/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":71881917,"identity":"7498db82-9ef9-40aa-9d43-534e2fc9b392","added_by":"auto","created_at":"2024-12-19 11:40:29","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":317782,"visible":true,"origin":"","legend":"\u003cp\u003ePhysical and schematic diagrams of the test apparatus: (a) physical diagram, (b) schematic diagram\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-5653720/v1/462e93c0d381f5b315412adb.png"},{"id":71882559,"identity":"f2a2567c-2ee3-4e48-b40f-19152fee5827","added_by":"auto","created_at":"2024-12-19 11:48:24","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":238212,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic structure of PAO\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-5653720/v1/406c2b1779f3b31dc942cc69.png"},{"id":71881903,"identity":"8ab2885a-dd6e-4bb1-afb8-9e6851fe3646","added_by":"auto","created_at":"2024-12-19 11:40:26","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":341558,"visible":true,"origin":"","legend":"\u003cp\u003eMolecular Modeling of Synthetic Gear Oil\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-5653720/v1/f58cf75b7738f2fc9b3ff139.png"},{"id":71881919,"identity":"a571d0bd-b629-4231-8d12-6fa79f167046","added_by":"auto","created_at":"2024-12-19 11:40:30","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":510639,"visible":true,"origin":"","legend":"\u003cp\u003eMolecular modeling of mineral oil\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-5653720/v1/5d9954abd769ebc88078f191.png"},{"id":71881918,"identity":"9f97e437-1222-4dc0-9df0-ccdb2e9630dd","added_by":"auto","created_at":"2024-12-19 11:40:29","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":316255,"visible":true,"origin":"","legend":"\u003cp\u003eModel of NDs (a) cellular model, (b) molecular model\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-5653720/v1/b12477dab70646bd605d9606.png"},{"id":71881897,"identity":"374efcaf-35dd-4625-ab72-bafbba64eb35","added_by":"auto","created_at":"2024-12-19 11:40:26","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":820793,"visible":true,"origin":"","legend":"\u003cp\u003eModel of NDs synthetic gear oil (a) 0.1 wt. % NDs, (b) 0.3 wt. % NDs, (c) 0.6 wt. % NDs\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-5653720/v1/fe20f5eadcca6113eb26850b.png"},{"id":71881904,"identity":"ffeb30fb-3744-4f82-9e50-831fadfc585b","added_by":"auto","created_at":"2024-12-19 11:40:27","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":896079,"visible":true,"origin":"","legend":"\u003cp\u003eModel of NDs mineral gear oil (a) 0.1 wt. % NDs, (b) 0.3 wt. % NDs, (c) 0.6 wt. % NDs\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-5653720/v1/a7917c85b987307c8a1254ef.png"},{"id":71881873,"identity":"99d6bf3f-bf3a-47ed-a393-0e67a1f08ba0","added_by":"auto","created_at":"2024-12-19 11:40:25","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":75908,"visible":true,"origin":"","legend":"\u003cp\u003eTemperature rise rate of dispersed 1 h gear oil: (a) test group 1, (b) test group 2, (c) test group 3\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-5653720/v1/64e7e9c38f322b12e443cadf.png"},{"id":71881783,"identity":"5706ac6d-7e10-406b-9f83-595cdfb4bade","added_by":"auto","created_at":"2024-12-19 11:40:14","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":68944,"visible":true,"origin":"","legend":"\u003cp\u003eTemperature rise rate of dispersed 96 h gear oil: (a) test group 1, (b) test group 2, (c) test group 3\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-5653720/v1/64d9a27ea42eb72242a21e8b.png"},{"id":71882564,"identity":"622735fa-58bc-4fc3-982c-9de51af658cb","added_by":"auto","created_at":"2024-12-19 11:48:30","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":38871,"visible":true,"origin":"","legend":"\u003cp\u003eThe synthetic oil model temperature change characteristics figure: (a) 298K, (b) 363K\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-5653720/v1/4ab0024272413da5395ac566.png"},{"id":71882560,"identity":"59a0da07-3bcf-4da1-9ef0-0ea0115998f8","added_by":"auto","created_at":"2024-12-19 11:48:24","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":41288,"visible":true,"origin":"","legend":"\u003cp\u003eThe mineral oil model temperature change characteristics figure: (a) 298K, (b) 363K\u003c/p\u003e","description":"","filename":"11.png","url":"https://assets-eu.researchsquare.com/files/rs-5653720/v1/e8e5042619a3ed1464dfa864.png"},{"id":72009022,"identity":"fb9a15c3-a833-4728-bea5-5a2f46048cc5","added_by":"auto","created_at":"2024-12-20 14:47:42","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4311241,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5653720/v1/c601db65-a279-4462-addb-36b0a262cd0e.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Study on the cooling performance of aviation gear oil with nanodiamonds as additives","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eAs a key component of the aviation transmission system, the lubrication status of gears directly affects the operational safety and performance stability of the aircraft [1]. Therefore, the development of high-performance, long-life aviation gear lubricating oil has become an important issue in the current aviation lubrication technology research [2]. During aircraft operation, aviation gears need to operate at high speeds, high temperatures, high pressures and other extreme conditions, which requires lubricating oil to have excellent extreme pressure, anti-wear, thermal stability and oxidation resistance [3\u0026ndash;5].\u003c/p\u003e \u003cp\u003eThe cooling performance of the lubricant is not only related to the normal operation of the equipment, but also closely related to the service life and efficiency of the equipment [6\u0026ndash;7]. The cooling performance of different types and formulations of lubricants may vary significantly [8\u0026ndash;10]. In recent years, the rapid development of nanotechnology has provided new solutions for aviation gear lubrication, and nano-lubricants have received widespread attention in the aviation field due to their unique anti-wear and friction reduction properties [11\u0026ndash;14]. Since Nanodiamonds have good thermal conductivity [15\u0026ndash;17] and lubricity [18\u0026ndash;20], so adding them to gear oil in the right amount can help improve the overall thermal conductivity of gear oil. Pico D F M et al [21] used POE synthetic refrigeration oil with two different mass fractions of synthetic diamond nanoparticles as a nano-lubricant in vapor compression refrigeration systems and showed that 0.1% and 0.5% nanodiamonds reduced friction and wear by about 4% and about 30%, respectively, and improved the coefficient of performance and cooling capacity. In addition, nanodiamond as an all-carbon nontoxic additive, is highly environmentally friendly and meets the environmental requirements for the development of aviation gear lubricants [22\u0026ndash;25]. However, despite the great potential of nanodiamond in aviation gear lubrication, the cooling mechanism of nanodiamond in gear oils is not fully understood.\u003c/p\u003e \u003cp\u003eIn this work, a temperature rise test setup was constructed with a thermostatic water bath to test the temperature rise of different variables of gear oil. To investigate the effects of nanodiamond content, gear oil type, dispersant type and other factors on the cooling performance of gear oil. Molecular dynamics simulations by constructing microscopic molecular models of gear oil. A microscopic investigation to reveal the mechanism of nanodiamond increased cooling performance on gear oil. The aim of this study was investigated in depth the effect of nanodiamonds as additives on the cooling performance of aviation gear oil, demonstrating the intrinsic mechanism of the nanodiamonds enhanced cooling performance of gear oil. It provided theoretical basis for the application of nanodiamond in aviation gear oil and promoted the further development of aviation gear lubrication technology.\u003c/p\u003e"},{"header":"2 Experimental details","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Materials and equipment\u003c/h2\u003e \u003cp\u003eTwo synthetic gear oils of different viscosity grades and one mineral gear oil were used as solvents (relevant information is shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Nanodiamonds of 10\u0026ndash;30 nm particle size was used as an additive (Zhen Drill Abrasives Co., Ltd.).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eTest gear oil\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGear oil brands and models\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTypes of gear oil\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eviscosity grade\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eShell 555\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003esynthetic oil\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e100\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTurbo Oil 2197\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003esynthetic oil\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e27\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMobil 600XP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003emineral oil\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e100\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe test equipment included single-well digital display constant temperature water bath, WST digital thermometer, precision electronic balance, electric stirrer and ultrasonic cleaner.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Test design of NDs gear oil temperature rise\u003c/h2\u003e \u003cp\u003eFirst, different contents (0.05 wt.%, 0.10 wt.%, 0.20 wt.%, 0.30 wt.%, 0.60 wt.%) of nanodiamonds were added to 50 ml of aviation gear oil (Test Group 1: Shell 555; Test Group 2: Turbo Oil 2197; Test Group 3: Mobil 600XP). Compounded into NDs gear oil. Mechanical stirring was carried out for 30 minutes by means of an electric stirrer to ensure that the NDs were effectively dispersed in the gear oil. Then 1 wt.% of the dispersant was added to the NDs gear oil. Dispersion was carried out by ultrasonication for 1 h and again by mechanical mixing for 30 min. Obtained NDs gear oil with different dispersion profiles. The NDs gear oil was transferred to a sealed test tube for storage.\u003c/p\u003e \u003cp\u003eConstruct a set of gear oil heating detection device using constant temperature water bath method. Simulate the high-temperature working conditions faced by gear oil in the actual working process. The experimental principle of the device is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(b). Three groups of test gear oil after dispersant dispersion for 1 h and 96 h were selected as the test objects for temperature rise test. Gears, as key components in mechanical equipment, usually operate in complex environments with high temperatures. Therefore, a water bath temperature of 90\u0026deg;C is used as a thermostatic source to transfer heat to the gear oil, and the rate of heating of the gear oil from 25\u0026deg;C to 65\u0026deg;C is tested.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Molecular modeling of NDs gear oil\u003c/h2\u003e \u003cp\u003e(1) Molecular modeling of synthetic oil\u003c/p\u003e \u003cp\u003ePAO (polyalphaolefin), as a synthetic base stock widely used in the field of gear oils, has a unique molecular structure and excellent performance characteristics that make it an important part of the development of industrial lubrication technology. The molecular structure consists mainly of relatively regular long-chain alkanes, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. The synthetic gear oil model containing 12 PAO monomer models was constructed by constructing an amorphous polymer, and the volume size of this amorphous cell model was 24.02 nm \u0026times; 24.02 nm \u0026times; 20.42 nm, as shown in Figure. 3.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e(2) Molecular modeling of mineral oil\u003c/p\u003e \u003cp\u003eMineral oil as a traditional lubricant base stock. Its composition is complex, mainly including chain alkanes, cycloalkanes and aromatic hydrocarbons and other hydrocarbons. In order to study more deeply the differences in microstructure and properties between mineral oil and synthetic oil, a mineral oil model based on cycloalkyl mineral oil components was constructed. Referring to the mass ratio of mineral oil components tested in the relevant literature [26]. By calculating the relative molecular mass of each component, the molar ratios of the components of the naphthenic mineral oil were obtained as shown in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComponent of naphthenic mineral oil\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eChain alkane\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"4\" nameend=\"c6\" namest=\"c3\"\u003e \u003cp\u003eTotal cycloalkanes\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eAromatic hydrocarbons\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eOne ring\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eTwo rings\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eThree rings\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eFour rings\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMolecular formula\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eC\u003csub\u003e12\u003c/sub\u003eH\u003csub\u003e26\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eC\u003csub\u003e14\u003c/sub\u003eH\u003csub\u003e28\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eC\u003csub\u003e13\u003c/sub\u003eH\u003csub\u003e24\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eC\u003csub\u003e16\u003c/sub\u003eH\u003csub\u003e28\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eC\u003csub\u003e16\u003c/sub\u003eH\u003csub\u003e26\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eC\u003csub\u003e19\u003c/sub\u003eH\u003csub\u003e30\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMass fraction %\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e11.67%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e17.28%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e24.07%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e24.69%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e14.81%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e7.48%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eUsing the method proposed by Theodorou et al [18] for the preparation of amorphous polymers. Six standard cycloalkyl mineral oil compositions were prepared in molar ratios to obtain standard amorphous mineral oil crystals as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. In order to make the simulation results more accurate, the relative molecular mass and cell volume of the mineral oil molecular model were further set up. Making it consistent with the synthetic oil model.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e(3) Molecular modeling of nanodiamonds\u003c/p\u003e \u003cp\u003eThe nanodiamond cell model and molecular model are shown in Figure. 5, and the volume size of the molecular model is set to 0.2 nm. Its molecular structure consists of carbon atoms connected in the form of sp3 hybridization, and each carbon atom is surrounded by four neighboring carbon atoms, forming a three-dimensional mesh structure.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e(4) Molecular modeling of NDs gear oil\u003c/p\u003e \u003cp\u003eThree of the five critical groups of nanodiamond content (0.1 wt.%, 0.3 wt.% and 0.6 wt.%) mentioned in the previous section were selected as the focus of the study. The nanodiamond molecular model was populated into the gear oil model according to three molar mass ratios. A synthetic oil model and a mineral oil model containing nanodiamond additives were constructed, respectively, as shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e and \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e. By comparing the structural and performance differences between these two models at the molecular level, an in-depth understanding of the interaction mechanism between nanodiamonds and different types of gear oils was obtained.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTwo molecular dynamics simulation temperatures, 298 K and 363 K, were set according to the test temperatures in the previous thermostatic water bath tests. four sets of gear oil models were explored for the temperature variation laws at room temperature and test temperatures, respectively. The simulation duration was set to 200 ps. Given that the COMPASS force field has been shown to accurately simulate the motion of small molecules in silica-alumina media [28\u0026ndash;29], it was chosen for structure optimization and molecular simulation. The Verlet velocity algorithm was used to solve Newton's equations to obtain the positions and kinetic energies of all atoms in the model at each time point. An atom-based approach was used to calculate the van der Waals forces. Ewald summation method is used to calculate the electrostatic forces.\u003c/p\u003e \u003c/div\u003e"},{"header":"3.Results and analysis","content":"\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Study of NDs gear oil temperature rise rate\u003c/h2\u003e \u003cp\u003eThe temperature rise rate of the three sets of test gear oil after dispersion for 1 h from 25\u0026deg;C to 65\u0026deg;C in a 90\u0026deg;C thermostatic water bath was obtained by calculation, and the data is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e. Of the three groups of gear oil without nanodiamonds. The gear oil in test group 1 (Shell 555, synthetic, viscosity grade 100) exhibited the lowest rate of temperature rise at 0.188\u0026deg;C/s. The gear oil in test group 2 (Turbo Oil 2197, synthetic, viscosity grade 27) exhibited a slightly higher rate of temperature rise at 0.198\u0026deg;C/s than test group 1. The gear oil in test group 3 (Mobil 600XP, mineral oil, viscosity grade 100) showed the highest rate of temperature rise at 0.204\u0026deg;C/s. All of the gear oil with nanodiamonds were temperature rise lower than the gear oil without nanodiamonds. When nanodiamond content reached 0.06 wt%, the temperature rise rate of each test gear oil reached the lowest value and gradually stabilized. Different dispersants had different effects on the temperature rise rate of the gear oil. In test group 1, the silane coupling agent group had the most significant cooling effect. Its lowest temperature rise rate was 0.145\u0026deg;C/s, which was 22.87% lower relative to the control gear oil. In experimental group 2, the oleic acid group showed the most significant temperature cooling effect. Its lowest temperature rise rate was 0.163\u0026deg;C/s, which was 17.68% lower relative to the control gear oil. In test group 3, the silane coupling agent group had the most significant temperature cooling effect. Its lowest temperature rise rate was 0.145\u0026deg;C/s, which was 11.27% lower than that of the control gear oil group. Among all the test groups after 1 h of dispersion, the silane coupling agent group in test group 1 had the lowest temperature rise rate.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe temperature rise rate data for the three sets of test gear oils after 96 h of dispersion from 25\u0026deg;C to 65\u0026deg;C in a 90\u0026deg;C thermostatic water bath is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e. Similar to the case of dispersion for 1 h, all test groups showed a decrease in the rate of temperature rise compared to the control group. When the nanodiamond content was at 0.6 wt.%, the test groups achieved the lowest temperature rise rate and gradually stabilized. Among the test 1 groups, the oleic acid group showed the most significant temperature cooling effect. Its lowest temperature rise rate was 0.165\u0026deg;C/s, which was 12.23% lower relative to the control gear oil. In test group 2, the oleic acid group has the most significant temperature cooling effect. The lowest temperature rise rate was 0.166\u0026deg;C/s, which was 16.16% lower than that of the control gear oil. In test group 3, the oleic acid group has the most significant temperature cooling effect. Its lowest temperature rise rate was 0.187\u0026deg;C/s, which was 8.33% lower than that of the control gear oil. In all test groups after 96 h of dispersion, the lowest temperature rise rate was in the oleic acid group, followed by the polyethylene glycol group, and the highest in the silane coupling agent group.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAs shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e and \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. In all test groups, the temperature rise rate of gear oil showed a decreasing trend with the addition of nanodiamonds. And with the further increase of NDs content, the temperature rise rate gradually decreased and stabilized. Nanodiamonds affect the cooling performance of synthetic oil significantly better than mineral oil. The best cooling effect of NDs synthetic oil was 2.03 times higher than NDs mineral oil. With the increase of dispersion time, the change in temperature rise rate after 96 h of dispersion was significantly reduced compared to the case of 1 h of dispersion. Among them, the oleic acid group showed the smallest change after 96 h of dispersion, the polyethylene glycol group was the second largest, and the silane coupling agent group showed the largest change.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Molecular dynamics simulation of NDs gear oil\u003c/h2\u003e \u003cp\u003eStructural optimization and annealing by COMPASS force field. Molecular dynamics simulations were performed. Deriving the temperature variation rule of four groups of test synthetic gear oil at different temperatures. As shown in Figure. 10.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe average temperatures for each set of modeled reactions were calculated as shown in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. The temperature differences between synthetic oil with nanodiamonds and without nanodiamonds were also comparatively analyzed. At the simulated temperature of 298 K, with the extension of simulation time, the average temperatures of the four combined synthetic oil models showed significant differences. The average temperatures of the synthetic oil model were 188.95 K, 183.32 K, 179.56 K, and 187.55 K, respectively, in order of NDs content from lowest to highest. This result tentatively suggested that synthetic oil spiked with nanodiamonds exhibit lower average temperatures at lower temperatures. Implying nanodiamonds may had a positive effect on the cooling performance of gear oil.\u003c/p\u003e \u003cp\u003eWhen the simulated temperature was increased to 363 K, the average temperatures of the synthetic oil model were 238.63 K, 218.73 K, 220.14 K, and 222.13 K, respectively. Compared to the results at 298 K, the overall temperature increased, and the synthetic oil with nanodiamonds still exhibited relatively low average temperatures. This further confirms the enhancement of the cooling performance of gear oil by nanodiamonds. In the two sets of molecular dynamics simulation results at different temperatures, the temperature of the synthetic oil reached the minimum in the range of 0.1 wt. % -0.3 wt. % of the NDs content.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eAverage temperatures of molecular model of test synthetic oil\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.0 wt.% NDs\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.1 wt.% NDs\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.3 wt.% NDs\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.6 wt.% NDs\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e298 K\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e188.95 K\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e183.32 K\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e179.56 K\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e187.55 K\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e363 K\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e238.63 K\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e218.73 K\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e220.14 K\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e222.13 K\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe molecular dynamics simulation of four groups of mineral gear oil model were carried out, and the temperature variation rules of four groups of test mineral gear oil at different temperature were derived as shown in Figure.11.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe average temperatures of the four groups of mineral gear oil at different setting temperatures were calculated as shown in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. At 298 K, with the extension of simulation time, the average temperatures of the four groups of mineral oil model were 195.55 K, 185.44 K, 190.30 K, and 190.71 K, respectively. At 363 K, the average temperatures were 243.59 K, 221.33 K, 221.09 K and 227.69 K, respectively. In the four groups of mineral oil model, the average temperatures of mineral oil with nanodiamonds were lower than those without nanodiamonds, which can prove that nanodiamonds can effectively enhance the cooling performance of mineral gear oil. At the same time, the average temperatures of the four groups of mineral oil model under two temperature fields were higher than those of the synthetic oil model, which can indicate that the molecular structure of synthetic oil was more stable and thermally stable than mineral oil.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eAverage temperatures of molecular model of test mineral oil\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.0 wt.% NDs\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.1 wt.% NDs\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.3 wt.% NDs\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.6 wt.% NDs\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e298 K\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e195.55 K\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e185.44 K\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e190.30 K\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e190.71 K\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e363 K\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e243.59 K\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e221.33 K\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e221.09 K\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e227.69 K\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eFrom a microscopic point of view, NDs act as additives in gear oil, and their microstructure provides a large amount of surface area to effectively adsorb and transfer heat. By filling microscopic defects and irregular surfaces in the oil, nanodiamonds are able to reduce localized hot spots in the oil and increase the heat conduction path, thus improving the thermal conductivity of the oil. At the same time, the interfacial interaction between nanodiamonds and oil molecules also plays a key role. The surface of the nanodiamonds is rich in functional groups, which can form hydrogen bonds, van der Waals forces and other interactions with the lubricant molecules, and improve the compatibility between the nanodiamonds and the oil. This interfacial interaction makes the nanodiamonds better dispersed in the fluid, and can effectively transfer heat and improve the thermal conductivity of the oil.\u003c/p\u003e \u003c/div\u003e"},{"header":"4.Conclusion","content":"\u003cp\u003eIn this study, the effects of nanodiamond content and dispersant type on the temperature rise rate of different types of aviation gear oil were investigated through gear oil temperature rise test. Combined with molecular dynamics simulation, the intrinsic mechanism of nanodiamond enhanced cooling performance of gear oil was investigated. The conclusions are as follows:\u003c/p\u003e \u003cp\u003e(1) Nanodiamonds had a better effect in enhancing the cooling performance of gear oil. In the range of 0.05 wt. % -0.6 wt. %, the temperature rise rate of the NDs gear oil gradually decreased and leveled off with the increase of NDs content.\u003c/p\u003e \u003cp\u003e(2) Nanodiamonds were more suitable for use as additives in synthetic oil. NDs synthetic oil had a 2.03 times greater cooling effect than NDs mineral oil. The effect of nanodiamonds on the cooling properties of gear oil decreased with the increase of dispersion time.\u003c/p\u003e \u003cp\u003e(3) The interfacial binding effect between NDs molecules and oil molecules. It could effectively improve the compatibility between nanodiamonds and gear oil and promote the dispersion of nanodiamonds in oil.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eDr. Wei: Conceptualization, Methodology, Validation, Project administration. Yang: Writing - Original Draft, Investigation. Xie: Resources. He: Visualization. Cao: Data Curation. Li: Formal analysis. Zhong: Visualization. Dr. Chen: Writing - Review \u0026amp; Editing.\u003c/p\u003e\u003ch2\u003eAcknowledgments\u003c/h2\u003e \u003cp\u003eThe authors are grateful for the financial support from the National Natural Science Foundation of China (Grant No. 52105055), National Natural Science Foundation of China (Grant No. 52475056), Natural Science Foundation of Hunan Province, (Grant No.2023JJ30281), Open Fund Project of Key Laboratory of Hunan Province for Efficient Power System and Intelligent Manufacturing (Grant No. 2022KF05), Aid Program for Science and Technology Innovative Research Team in Higher Educational Institutions of Hunan Province(High Performance Manufacturing Processes and Service Performance Optimization).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eZhao J, Sheng W, Li Z, et al. Effect of lubricant selection on the wear characteristics of spur gear under oil-air mixed lubrication[J]. Tribology International, 2022, 167: 107382.\u003c/li\u003e\n \u003cli\u003eLi L, Wang S, Zhang X, et al. Numerical Calculation Analysis and Characteristic Research on Windage Loss of Oil-Jet Lubricated Aviation Gear Pair[J]. International Journal of Aerospace Engineering,2022,2022.\u003c/li\u003e\n \u003cli\u003eJie Z, Min Y, Arndt J, et al. Characterising the effects of simultaneous water and gasoline dilution on lubricant performance [J]. Tribology International, 2023, 179\u003c/li\u003e\n \u003cli\u003eUrmilla B, Maitrayee S, J. I B, et al. Functionalized polyethylene on property enhancement of lubricating oil and their performance evaluation study [J]. Journal of Applied Polymer Science, 2022, 140 (4):\u003c/li\u003e\n \u003cli\u003ePratap A S, Kumar R D, Amit S. Influence of nano particles on the performance parameters of lube oil \u0026ndash; a review [J]. Materials Research Express, 2021, 8 (10):\u003c/li\u003e\n \u003cli\u003eSaidur R, Kazi S N, Hossain M S, et al. A review on the performance of nanoparticles suspended with refrigerants and lubricating oils in refrigeration systems[J]. Renewable and Sustainable Energy Reviews, 2011, 15(1): 310-323.\u003c/li\u003e\n \u003cli\u003eKobasko N I, Souza E C D, Canale L D C F, et al. Vegetable Oil Quenchants: Calculation and Comparison of The Cooling Properties of a Series of Vegetable Oils[J]. Strojniski Vestnik, 2010, 56(2).\u003c/li\u003e\n \u003cli\u003eMuhammad J, Ning H, Wei Z, et al. Tribological behavior of WC-6Co against Ti\u0026ndash;6Al\u0026ndash;4V alloy under novel cryogenic ethanol-ester oil dry-ice hybrid lubri-cooling[J]. Tribology International,2021,156106812-.\u003c/li\u003e\n \u003cli\u003ePinheiro C T, Pais R F, Ferreira A G M, et al. Measurement and correlation of thermophysical properties of waste lubricant oil[J]. The Journal of Chemical Thermodynamics, 2018, 116: 137-146.\u003c/li\u003e\n \u003cli\u003ePereira O, Rodr\u0026iacute;guez A, Ayesta I, et al. A cryo lubri-coolant approach for finish milling of aeronautical hard-to-cut materials[J]. Int. J. of Mechatronics and Manufacturing Systems,2016,9(4):370-384.\u003c/li\u003e\n \u003cli\u003eDuan Z, Wang S, Wang Z, et al. Tool wear mechanisms in cold plasma and nano-lubricant multi-energy field coupled micro-milling of Al-Li alloy[J]. Tribology International, 2024,192109337-.\u003c/li\u003e\n \u003cli\u003eMa L, Ma L, Ma X, et al. Tribological Properties and Lubrication Mechanisms of Water-Based Nanolubricants Containing TiO 2Nanoparticles during Micro Rolling of Titanium Foils[J]. Materials,2023, 17(1).\u003c/li\u003e\n \u003cli\u003eMu\u0026rsquo;taz A, Salloom A. The effect of nanolubrication on wear and friction resistance between sliding surfaces[J]. Industrial Lubrication and Tribology, 2023, 75(5): 526-535.\u003c/li\u003e\n \u003cli\u003eWeiwei T, Yi W, Xuejun Z, et al. Graphitic carbon nitride quantum dots as novel and efficient friction-reduction and anti-wear additives for water-based lubrication[J]. Wear, 2023, 528-529.\u003c/li\u003e\n \u003cli\u003eTianhao A, Wutong F, Zhonglai R, et al.Simultaneous enhancement of mechanical performance and thermal conductivity for polyamide 10T by nanodiamond compositing[J].Journal of Applied Polymer Science,2021,139(19):\u003c/li\u003e\n \u003cli\u003eAleksei V, Sergey K, Alexander V, et al.Hardness and thermal conductivity of a composite based on aluminum modified with a hybrid material detonation nanodiamond/few-layer graphene[J].Fullerenes, Nanotubes and Carbon Nanostructures,2022,30(1):205-210.\u003c/li\u003e\n \u003cli\u003eChaoyu W, Junqi S, Zhi H, et al. Flexible silicone rubber/carbon fiber/nano-diamond composites with enhanced thermal conductivity via reducing the interface thermal resistance[J]. Journal of Polymer Engineering,2022,42(6):544-553.\u003c/li\u003e\n \u003cli\u003eShuqing C, Qi D, Yan G, et al. Study of Tribological Properties of Fullerenol and Nanodiamonds as Additives in Water-Based Lubricants for Amorphous Carbon (a-C) Coatings[J]. Nanomaterials,2021,12(1):139-139.\u003c/li\u003e\n \u003cli\u003eAbdulhakeem J, Bibin J. Tribological performance of nanolubricants dispersed with graphene oxide and detonation nanodiamond[J]. Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology,2021,235(9):1937-1949.\u003c/li\u003e\n \u003cli\u003eRuoxuan H, Shinan H, Tianchi Z, et al. Characterization and tribology performance of polyaniline-coated nanodiamond lubricant additives[J]. Nanotechnology Reviews,2022,11(1):2190-2201.\u003c/li\u003e\n \u003cli\u003ePico D F M, da Silva L R R, Mendoza O S H, et al. Experimental study on thermal and tribological performance of diamond nanolubricants applied to a refrigeration system using R32[J]. International Journal of Heat and Mass Transfer, 2020, 152: 119493.\u003c/li\u003e\n \u003cli\u003eWenshuang H, Minjie W, Jianxin R, et al. Effect of functionalized nanodiamond on properties of polylactic acid eco-friendly composite films[J]. Diamond \u0026amp; Related Materials,2023,133.\u003c/li\u003e\n \u003cli\u003eMostovoy A, Bekeshev A, Shcherbakov A, et al. Investigating the Structure and Properties of Epoxy Nanocomposites Containing Nanodiamonds Modified with Aminoacetic Acid[J]. Polymers,2024,16(4).\u003c/li\u003e\n \u003cli\u003eTorres‐Sanchez C, Balodimos N. Effective and Eco‐friendly Lubrication Protocol Using Nanodiamonds in a Dry Regime for Conveyor Systems in the Beverage Industry[J].Packaging Technology and Science,2017,30(5):209-218.\u003c/li\u003e\n \u003cli\u003eChun Z, Mufan A, Minjie W, et al. Effect of curcumin-modified nanodiamonds on properties of eco-friendly polylactic acid composite films[J]. Colloids and Surfaces A: Physicochemical and Engineering Aspects,2024,680.\u003c/li\u003e\n \u003cli\u003eLiu F, Xu W. Characteristic comparison between paraf-fine-base and naphthene-base transformer oils[J]. Transformer, 2004, 41(7): 27-30.\u003c/li\u003e\n \u003cli\u003eTheodorou Doros N., Suter Ulrich W. Detailed molecular structure of a vinyl polymer glass[J]. Macromolecules, 1985, 18(7): 1467-1478.\u003c/li\u003e\n \u003cli\u003eLi Y, Zhang X, Ye F, et al. Influence regularity of O2 on dielectric and decomposition properties of C4F7N-CO2-O2 gas mixture for MV equipment[J]. \u0026nbsp;Hig h Voltage, 2020, 5(3): 256-263.\u003c/li\u003e\n \u003cli\u003eChen Z. Theory and Practice of Molecular Simulation[M]. Beijing: Chemical Industry Press, 2007: 6-18.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"aviation gear oil, nanodiamonds, cooling performance, molecular dynamics simulation","lastPublishedDoi":"10.21203/rs.3.rs-5653720/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5653720/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIn order to enhance the service performance of aviation gear oil. This work studied the effect on the cooling performance of aviation gear oil with nanodiamonds (NDs) as additives. Different contents (0.05 wt.%, 0.10 wt.%, 0.20 wt.%, 0.30 wt.%, 0.60 wt.%) of NDs were added into aviation gear oil, and different dispersants were used to disperse the NDs, which were compounded into highly dispersible NDs gear oils. Temperature rise tested by thermostatic water bath device. Molecular modeling to simulate the microscopic mechanism of nanodiamonds interaction with gear oil. The results showed that nanodiamonds could effectively enhance the cooling performance of aviation gear oil. The cooling performance was better with the increase of NDs content, which tended to stabilize at 0.6 wt.%. It was improved by 22.87% relative to the control. The longer the dispersion time, the worse the cooling performance of NDs gear oil. The interfacial bonding between the NDs molecules and the oil molecules enhanced the cooling rate of the gear oil. This study revealed the intrinsic mechanism of nanodiamonds as additives to enhance the cooling performance of gear oil. It provided theoretical guidance for the application of aviation gear oil and provided guarantee for the smooth operation of aviation equipment.\u003c/p\u003e","manuscriptTitle":"Study on the cooling performance of aviation gear oil with nanodiamonds as additives","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-12-19 11:38:54","doi":"10.21203/rs.3.rs-5653720/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"1634a061-229b-4d39-b329-6e2a7f07e13e","owner":[],"postedDate":"December 19th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-12-20T14:39:27+00:00","versionOfRecord":[],"versionCreatedAt":"2024-12-19 11:38:54","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5653720","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5653720","identity":"rs-5653720","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}