Study On Thermal Elastohydrodynamic Lubrication Mechanism For Ferrofluid Lubricated Involute Spur Gears

With the development and progress of aerospace manufacturing industry,lubrication technology in extreme environment has been paid more and more attention by researchers.Modern machinery,especially high-tech machinery such as aviation,aerospace and weapons,often works in extreme environments.And conventional lubrication materials are difficult to solve the friction problems under these extraordinary conditions.Aviation engine friction function components such as gears work for long periods of time in extreme environmental conditions such as high temperature,high speed and heavy load,so the lubrication conditions are very harsh.Meantime gears are required to work reliably in starved lubrication conditions.Magnetic fluids can accurately fill the lubricated surface while preventing leakage,and have been lubricated the rolling and sliding surfaces in contact with each other.In this paper,the ferrofluid lubrication numerical model of the involute spur gear is established with the aeronautical engine.On the basis of the development of the former program,the calculation program of the ferrofluid lubrication of the gears is written.Multigrid method and multigrid integral method based on continuous medium mechanics is applied.The dimensionless equations were discretized by finite difference method and and the temperature was calculated by column scanning method.Taking into account the load spectral characteristics of gears under different environmental conditions,the numerical simulation research is carried out.This paper puts forward the idea of ferrofluid directional geotechnical intelligent regulation of oil lubrication,and analyzes the comprehensive influence mechanism of multiphysics coupling on the gear lubrication film.The effects of magnetic particles under different base carrier fluids and different volume fractions on lubrication performance were studied.Because the magnetic particles in ferrofluid are greatly affected by the base carrier fluid,so the influence of the gear ferrofluid lubrication film is analyzed by exploring the composition,viscosity and density characteristics.Magnetic particles increase the density and viscosity of lubricants to a certain extent.When the load force is small,magnetic particles and surfactant will form a chain structure.This structure can significantly increase the thickness and strength of the lubricant film,improving the ferrofluid lubrication performance.Meantime,considering the effect of the thermal effect by viscousshearing and compression and the impact load on oil pressure profile and film thickness.It has some reference value for guiding experimental design and engineering calculation.Considering the non-Newtonian characteristics of ferrofluid lubricantion,magnetic particles and thermal effect,to derive the Reynolds equation suitable for ferrofluid lubrication and establish a numerical model of ferrofluid lubrication for the involute spur gear.The shear stress of Ree-Eyring non-Newtonian ferrofluid has an important effect on the pressure profile,film thickness,friction coefficient and maximum temperature rise.When the load and the strain rate is too high,the calculation of Newton fluid is conservative,overestimating the temperature-viscosity wedge effect.Therefore,the lubrication analysis of non-Newtonian effect should not ignored.Based on the numerical simulation of ferrofluid lubrication theory,the influence mechanism of ferrofluid on the continuity of gear lubrication film is explored.The comparative analysis of ferrofluid lubrication performance under magnetic and no magnetic field conditions was carried.This paper explored the characteristics of ferrofluid viscosity and density distribution under different magnetic field strength,and studied the effect of magnetic field strength on the lubrication performance of ferrofluid.Magnetic particles have a similar“ball” effect,when the magnetic induction strength increases,the film thickness increases,the "microbearing" effect is more obvious and the friction coefficient decrease.In order to verify the reliability and accuracy of numerical calculation results,according to the minimum film thickness formula revised by Dowson in 1967.The relative error of the numerical results and empirical values is less than 10%,which can indirectly prove the accuracy and reliability of the numerical calculation results.