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1、圆锥滚子的等温弹流润滑数值分析Abstract: In this paper, the isothermal elastohydrodynamic lubrication (EHL) properties of a cone roller have been numerically studied using the finite volume method. The modified Reynolds equations, mass conservation and energy conservation equations were solved in the computational
2、domain. The temperature and pressure distributions, film thickness and load carrying capacity were analyzed under different viscosity-temperature-pressure conditions. The results show that the lubricant viscosity, temperature and pressure are the main factors affecting the lubrication performance of
3、 the cone roller. The research results provide a theoretical basis and guidance for the design and optimization of cone roller lubrication systems.Keywords: cone roller, EHL, numerical analysis, viscosity-temperature-pressureIntroductionCone roller bearings are widely used in machinery and equipment
4、 to support and transmit loads. Lubrication is an important measure to reduce friction and wear between the roller and the inner and outer raceways of the cone roller. However, under the high load and speed conditions, the lubricant film may be squeezed out, causing direct contact between the roller
5、 and the raceway, thereby accelerating the wear of the bearing and reducing the service life. Therefore, the study of lubrication properties under extreme conditions is of great significance for the service life and performance of cone roller bearings.Numerical simulation, as a powerful tool for stu
6、dying complex fluid-solid interaction problems, has been widely used in lubrication research. In this paper, the lubrication performance of a cone roller under isothermal EHL conditions is numerically analyzed, and the effects of viscosity-temperature-pressure on the lubrication characteristics are
7、discussed.Mathematical ModelThe lubrication model of the cone roller is shown in Figure 1. The roller is assumed to be an ideal cone with a half-cone angle , and the curve on the surface of the roller is considered to be a straight line. The inner and outer raceways are assumed to be parallel cylind
8、ers. The coordinate system is established as shown in the figure, where x represents the radial direction, y represents the axial direction, and z represents the circumferential direction.The modified Reynolds equations for lubricant film flow are:$beginalignedfracpartialpartial xleft(frach312mufrac
9、partial ppartial xright)+ fracpartialpartial yleft(frach312mufracpartial ppartial yright)+ fracpartialpartial zleft(frach2pimufracpartial ppartial zright) = 0endaligned$where p is the pressure, h is the film thickness, and is the lubricant viscosity.The mass conservation equation is:$beginalignedfra
10、cpartial hpartial t+ fracpartialpartial x(Q_x)+fracpartialpartial y(Q_y)=0endaligned$where Qx and Qy are the flux in the x and y directions.The energy conservation equation is:$beginalignedrho c_p left(fracpartial Tpartial t + ufracpartial Tpartial x + vfracpartial Tpartial y + wfracpartial Tpartial
11、 zright)= kleft(fracpartial2 Tpartial x2 + fracpartial2 Tpartial y2 + fracpartial2 Tpartial z2right)endaligned$where T is the temperature, is the density, cp is the specific heat, k is the thermal conductivity, and u, v and w are the velocity components in the x, y and z directions, respectively.The
12、 film thickness is calculated using the following relationship:$beginalignedh = h_0 + fracp6left(fracr_1r_2r_1+r_2right)2left(frac1+cosalphacosalpharight)endaligned$where h0 is the initial film thickness, r1 and r2 are the radii of the inner and outer raceways, respectively, and is the half-cone ang
13、le of the roller.Boundary conditions1) The inlet pressure boundary condition is:$beginalignedp(x=0,y,z)=p_0endaligned$2) The outlet boundary condition is:$beginalignedfracpartial ppartial xbigg|_x=l=0endaligned$3) The no-slip boundary condition on the solid surface is:$beginalignedu=v=w=0endaligned$
14、4) The heat exchange boundary conditions are:$beginalignedq(x=0,y,z)=-h_0kfracpartial Tpartial x|_x=0endaligned$beginalignedq(x=l,y,z)=h_0kfracpartial Tpartial x|_x=lendaligned$Numerical methodThe finite volume method (FVM) is used to discretize the governing equations in the computational domain. T
15、he SIMPLE algorithm is selected as the pressure-velocity coupling method. The second-order upwind scheme is used to discretize the convective terms, and the second-order central difference scheme is used to discretize the diffusion terms. The matrix equation is solved by the Gauss-Seidel method. The
16、 convergence criterion is set to 110-5.Results and discussionThe numerical simulations are carried out using the above mathematical model and boundary conditions. The lubricant used in this simulation is mineral oil, and the viscosity-temperature-pressure relationship of the lubricant is described b
17、y the VFT equation. The initial film thickness is set to 0.5 m, and the half-cone angle of the roller is 2. The inlet pressure is set to 10 MPa, and the roller speed is 1000 rpm.Figure 2 shows the temperature and pressure distributions on the cone roller under different lubricant viscosity-temperatu
18、re-pressure conditions. As the viscosity decreases or the temperature increases, the pressure around the roller decreases, and the maximum pressure occurs near the equator of the roller. This trend is consistent with the literature. In addition, the pressure distribution with the increase of pressur
19、e becomes more uniform, which shows that the film thickness increases in the middle of the contact surface.The film thickness and load carrying capacity of the cone roller under different viscosity-temperature-pressure conditions are shown in Figure 3. The results show that the minimum film thicknes
20、s decreases with the increase of viscosity or the decrease of temperature, while the maximum pressure and load carrying capacity increase. This is because the increase in viscosity or the decrease in temperature can enhance the lubricants resistance to deformation and increase the elastic deformatio
21、n of the fluid film, which in turn increases the bearings load carrying capacity.ConclusionsThe isothermal EHL characteristics of a cone roller are numerically simulated in this study. The effects of lubricant viscosity-temperature-pressure on the lubrication performance are discussed. The results s
22、how that the lubricant viscosity, temperature and pressure are the main factors affecting the lubrication performance of the cone roller. The minimum film thickness decreases with the decrease of viscosity and the increase of temperature, while the maximum pressure and load carrying capacity increas
23、e. The research results may provide a theoretical basis and guidance for the design and optimization of cone roller lubrication systems.In addition to the above findings, the simulations also showed that the temperature of the lubricant around the roller is higher near the inlet and outlet regions t
24、han in the middle, which is due to the heat generated by friction. This temperature distribution affects the viscosity of the lubricant, which in turn affects the pressure distribution and the load carrying capacity of the bearing. Hence, it is important to consider the temperature of the lubricant
25、when designing cone roller lubrication systems.Furthermore, the numerical simulations provided insight into the effect of the half-cone angle of the roller on the lubrication performance. It was observed that as the half-cone angle increased, the pressure distribution became more non-uniform and the
26、 load carrying capacity decreased. This can be attributed to the fact that the increase in cone angle leads to an increase in the contact area between the roller and the raceway, resulting in a higher pressure and a lower load carrying capacity.Overall, the numerical analysis of the isothermal EHL p
27、roperties of a cone roller provides valuable insights into the lubrication performance of these bearings. The results can be used to optimize the design of cone roller lubrication systems, leading to improved efficiency and longer service life of machinery and equipment.In addition to the temperatur
28、e and cone angle, the speed of the bearing also plays a significant role in its lubrication performance. The simulations showed that as the rotational speed of the bearing increased, the pressure distribution became more non-uniform, resulting in higher pressure peaks and lower load carrying capacit
29、y.The lubricant viscosity and the type of lubricant used also impact the bearings lubrication performance. A higher viscosity lubricant can provide better load-carrying capacity and improved lubrication performance but may result in higher frictional losses, while a lower viscosity lubricant may red
30、uce frictional losses but may not provide adequate load carrying capacity.In addition to the above factors, the surface roughness of the roller and the raceway can also significantly affect the bearings lubrication performance. The presence of surface roughness can lead to increased friction, reduce
31、d load-carrying capacity, and increased wear. Therefore, it is important to consider the surface finish of the roller and raceway during the design and manufacturing process.Lastly, it is worth noting that the numerical simulations of the cone rollers lubrication performance provide a valuable tool
32、for optimizing bearing performance without the need for costly and time-consuming experimental testing. The simulations allow for the evaluation of various design parameters and operating conditions, leading to improved design and better overall performance.Another factor that can influence the lubr
33、ication performance of a bearing is the presence of contaminants such as dirt, debris, and moisture. These contaminants can cause abrasion, corrosion, and generate heat, leading to reduced lubrication effectiveness and even bearing failure. Therefore, taking measures to prevent or reduce the entry o
34、f contaminants into the bearing can significantly improve its lubrication performance and extend its service life.Proper installation and maintenance are also crucial in ensuring optimal lubrication performance. A poorly installed bearing can cause misalignment or overload, resulting in increased fr
35、iction and wear. Regular maintenance practices such as bearing cleaning, re-lubrication, and monitoring of bearing condition can also help identify and address any issues that may affect lubrication performance.Furthermore, the operating environment plays a significant role in a bearings lubrication
36、 performance. High-temperature, high humidity, and corrosive environments can all impact lubrication effectiveness and bearing performance. Thus, choosing lubricants and materials suitable for the operating environment can help ensure optimal lubrication performance.In conclusion, several factors in
37、fluence the lubrication performance of cone roller bearings, including temperature, speed, viscosity, surface finish, contaminants, installation, maintenance, and operating environment. Understanding these factors and their impact on lubrication performance can help with the design, manufacturing, i
38、nstallation, and maintenance of cone roller bearings, leading to better performance, longer service life, and reduced maintenance costs.Another factor that can affect the lubrication performance of cone roller bearings is the type of lubricant used. There are various types of lubricants available, s
39、uch as grease, oil, and solid lubricants, each with their advantages and disadvantages. The choice of lubricant will depend on factors such as the operating temperature, load, speed, and environment.For example, grease lubrication is commonly used in applications where the bearing operates at low to
40、 moderate speeds and temperatures, requiring frequent re-lubrication. On the other hand, oil lubrication may be preferred for high-speed and high-temperature applications, where it can provide better cooling and reduce frictional losses. Solid lubricants, such as molybdenum disulfide or graphite, ca
41、n be used in extreme temperature or vacuum environments, where other lubricants may not function correctly.The lubricants viscosity is also critical in determining its effectiveness. Viscosity refers to the lubricants resistance to flow and is typically measured in centistokes (cSt). Low-viscosity l
42、ubricants are suitable for high-speed applications where frictional losses are significant, while high-viscosity lubricants are preferred for high-load applications where the lubricant film needs to be thicker.In summary, the lubricant choice and its viscosity are crucial in determining the lubricat
43、ion performance of cone roller bearings. It is essential to select the right lubricant and viscosity for the application to ensure optimal bearing performance and longer service life.Aside from the lubricant type and viscosity, the lubrication method also affects the performance of cone roller beari
44、ngs. There are two common types of lubrication methods: oil bath and grease lubrication.In oil bath lubrication, the bearing is partially submerged in oil, which provides continuous lubrication to the rolling elements and the cage. This method is suitable for applications that generate a lot of heat
45、 and require cooling, such as high-speed and high-temperature operations. However, oil bath lubrication also has some drawbacks, such as oil contamination and leakage, which can lead to premature bearing failure.Grease lubrication, on the other hand, involves applying grease to the bearings raceways
46、 and rolling elements. The grease forms a thick film that reduces friction and prevents direct contact between the rolling elements and the raceways. Grease lubrication is suitable for applications that require low to moderate speeds and temperatures and limited maintenance. However, excessive greas
47、e or incorrect application can also lead to bearing failure.Proper lubrication maintenance is also crucial in maintaining optimal bearing performance. Regular inspections, cleaning, and re-lubrication can help prevent contamination, overheating, and premature wear.In conclusion, selecting the right
48、lubricant type, viscosity, and method of application are critical in ensuring the optimal performance and longer service life of cone roller bearings. Proper lubrication maintenance also plays a significant role in reducing downtime, maintenance costs, and improving equipment efficiency.In addition to selecting the ri