How does the addition of various additives affect the viscosity of lubricants?5 answersThe addition of various additives significantly influences the viscosity of lubricants, impacting their performance across different temperatures and conditions. Fly-ash additives, for instance, have been shown to increase the viscosity of lubricating oils, with notable increments observed across different temperatures, thereby enhancing the lubricant's resistance to viscosity loss at elevated temperatures. Similarly, the introduction of viscosity index improvers (VII) like olefin copolymer (OCP) and other polymeric additives can either increase or decrease the efficiency of VII, depending on the type of base oil and the concentration of the additive used, illustrating the complex relationship between additive formulations and lubricant viscosity.
Viscosity modifiers, which are high molecular weight polymers, play a crucial role by increasing the viscosity of lubricating oils and ensuring efficient performance over a wide range of temperatures through their thickening efficiency and shear stability. The addition of specific chemical substances, such as antioxidants, friction modifiers, and viscosity index improvers, further improves the lubricant's properties by interacting with the base fluid to enhance performance in various industrial applications.
Moreover, additives designed to temporarily reduce viscosity in oil-based fluids demonstrate the versatility of additive technology in adjusting lubricant viscosity according to specific requirements. The effect of additives on kinematic viscosity has also been observed, where certain additives lead to a decrease in viscosity at higher concentrations, thereby increasing the lubricant's viscosity index.
Research into the pressure–viscosity coefficient highlights the temperature- and pressure-dependent changes in viscosity, indicating the significant role of polymer additives in these dynamics. Nanoparticle additives, such as yttrium oxide nanosheets, have been found to reduce the viscosity of mineral oil, offering insights into the design of next-generation lubricants with improved lubricating properties. Lastly, the study of polymethylmethacrylate (PMMA) as a gelling additive in synthetic base oil reveals the impact of molecular weight and concentration on the viscosity and non-Newtonian behavior of lubricants, emphasizing the importance of additive selection in lubricant formulation.
What types of nanoparticles enhance aluminum composite mechanical properties?5 answersVarious types of nanoparticles have been studied for their impact on enhancing the mechanical properties of aluminum composites. Alumina (Al2O3), titanium dioxide (TiO2), yttrium oxide (Y2O3), and zirconia (ZrO2) nanoparticles have shown significant improvements in mechanical properties when added to aluminum matrices. Studies have demonstrated that the addition of these nanoparticles leads to enhancements in tensile strength, yield strength, compression strength, micro-hardness, impact strength, wear resistance, and hardness of the resulting aluminum nanocomposites. The dispersion of nanoparticles in the aluminum matrix, along with factors like concentration and fabrication techniques, plays a crucial role in achieving these improvements. The use of various nanoparticles in aluminum composites presents a promising avenue for developing advanced materials with superior mechanical characteristics.
HBN nanoparticle using as lubricant additives?4 answersHexagonal boron nitride (h-BN) nanoparticles have been investigated as lubricant additives in several studies. The addition of h-BN particles to lithium grease has shown reductions in wear scar diameter and friction coefficients, leading to enhanced wear resistance and friction reduction. When h-BN nanoparticles were used in combination with g-C3N4 nanosheets as lubricating additives to white oil, the lubricating properties were further improved, resulting in reduced friction coefficients and wear rates. The use of commercial h-BN flakes mixed with nickel nanoparticles has also been explored, demonstrating the formation of antifriction and antiwear coatings on stainless steel substrates, leading to significantly improved friction and wear performance. Overall, the research suggests that h-BN nanoparticles have promising potential as lubricant additives, offering enhanced tribological properties and improved lubrication performance.
How rotor will help with the circulation of the waterturbine.?3 answersThe rotor in a water turbine helps with the circulation of water by directing the flow and cooling the rotor. In one paper, a rotor for transforming free flows in flow devices is described. The rotor body has an impingement surface with exit openings and lamellae, which create a larger cross-section for the flowing medium when the rotor is flown against. Another paper discusses a high-temperature rotor water circulating cooling device. The device includes a water flow passage inside the rotor body, which allows the cooling water to circulate and take away the heat generated by the high-speed rotation of the rotor. Additionally, a fluid flow turbine is mentioned, where the rotor and vanes are positioned to direct the fluid flow to one side of the rotor axis, aiding in the circulation of water. These rotor designs contribute to the efficient circulation and cooling of water in water turbines.
How does the lubrication of metal surfaces affect their friction and wear properties?4 answersLubrication plays a crucial role in minimizing the losses associated with wear by decreasing the mating surface friction. The friction and wear properties of carburized steel sliding with different materials were analyzed, and it was found that ZrO2 and carburizing steel have better tribological properties. A new active friction control method using a morphing surface was proposed, where the reduction of solid contact due to improvement of lubrication condition was likely the friction reduction mechanism. The composition of steel affects its properties such as hardness, which in turn affects wear. In the case of PEEK/steel contact, lubrication with poly-α-olefin (PAO) affected the formation and removal of PEEK transfer films, which influenced the tribological behavior.
How do nano additives and surfactants affect the dynamic behavior of droplets in two-phase flow?3 answersNano additives and surfactants have significant effects on the dynamic behavior of droplets in two-phase flow. The addition of hydrophobic particles leads to contact line pinning and receding breakup of droplets, while hydrophilic particles have little effect on droplet dynamics. Surfactants, such as 1-octanol, prevent bubble coalescence and enhance interfacial area in gas-liquid flow, resulting in smaller diameter bubbles and decreased bubble velocity. The presence of insoluble surfactants near the three-phase contact line increases local viscosity and friction, leading to restrained maximum retraction height and vertical oscillatory relaxation time of droplets. In addition, surfactants can affect droplet deformation and merging by reducing interfacial tension and generating Marangoni forces. These findings demonstrate that nano additives and surfactants play a crucial role in controlling the dynamic behavior of droplets in two-phase flow.