Effect of using hybrid nano lubricant on the thermo-hydrodynamic performance of two lobe journal bearings

2021 ◽  
pp. 135065012110530
Author(s):  
Abolfazl Rasoolizadeh Shooroki ◽  
Asghar Dashti Rahmatabadi ◽  
Mahdi Zare Mehrjardi
Keyword(s):  
Carrying Capacity ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Journal Bearings ◽  
Nano Particles ◽  
Load Carrying Capacity ◽  
Load Carrying ◽  
Nano Lubricant ◽  
Carbon Nano Tubes ◽  
Multiwall Carbon

Due to the wide range of journal bearings applications in the industrial machine, significant efforts have been made by tribology researchers to improve their performance in recent years. Designing new bearings geometry and using lubricants with new chemical compounds including additives are the most common solutions proposed to enhance the performance of journal bearing supports. New advancements in nanotechnology and producing the various types of nano particles have provided the chance of upgrading the properties of commercial lubricants. According to the different effect of nano fluids on the performance of mechanical systems corresponding to their composition, today they are used to achieve different goals in lubrication systems. Upgrading the steady state performance parameters including load carrying capacity, attitude angle, surface cooling and effective viscosity are among the expected results of applying nano lubricant in journal bearings. So, in this study the performance of hydrodynamic two lobe journal bearings lubricated with SiO2-multiwall carbon nano tubes /SAE40 hybrid nano fluid is presented considering the thermal effects. For this purpose, the governing Reynolds and energy equations as well as the equation of heat transfer in bearing shell are modified based on the properties of assumed rotor-bearing system. Then the effects of solid volume fraction of nano particles on the performance of two lobe bearings are studied for different amount of bearing noncircularity. The results indicate that upgrading the solid volume fraction of added nano particle to the SAE40 base oil, enhances the lubricant pressure distribution, load carrying capacity, and lubricant effective viscosity. Further, by increasing the solid volume fraction, the attitude angle and temperature of lubricant and rotor-bearing surfaces experience a decreasing trend. Generally, it's obvious from the results that choosing the appropriate solid volume fraction of SiO2-multiwall carbon nano tubes in hybrid nano oil composition, especially for high value of preload factor, can improve the performance of two lobe bearings.

Overall Characteristics of Bearings Lubricated With Ferrofluids

1983 ◽  
Vol 105 (3) ◽  
pp. 466-475 ◽  
Author(s):  
N. Tipei
Keyword(s):  
Boundary Conditions ◽  
Carrying Capacity ◽  
Magnetic Particle ◽  
Journal Bearings ◽  
Load Carrying Capacity ◽  
Pressure Center ◽  
Friction Forces ◽  
Flow Rates ◽  
Load Carrying ◽  
Side Flow

Using the results shown in some previous papers, the overall characteristics of bearings lubricated with ferrofluids are calculated. First, the load carrying capacity of infinitely long sliding and journal bearings is considered. The pressure center and the attitude angle are also determined. Then, similar characteristics of finite bearings are obtained. In both cases, the new boundary conditions and the actual film extent under magnetic stresses are taken into account. It is shown that friction forces are mainly affected by the change in viscosity due to magnetic particle suspensions, while magnetic stresses modify friction only under special conditions which usually are not met in lubrication. In addition, the flow rates and the side flow coefficients are calculated. It is shown that the lubricant leakage can be reduced and even avoided when proper measures are taken. For short bearings, diagrams are given for the film extent, the film boundaries, the load carrying capacity, and the attitude of the journal center.

Dynamic stability analysis of noncircular two-lobe journal bearings with couple stress lubricant regime

2020 ◽  
pp. 135065012094551
Author(s):  
Mahdi Zare Mehrjardi
Keyword(s):  
Steady State ◽  
Carrying Capacity ◽  
Couple Stress ◽  
Journal Bearings ◽  
Lubricating Oil ◽  
Couple Stress Fluid ◽  
Load Carrying Capacity ◽  
Stress Parameter ◽  
Attitude Angle ◽  
Load Carrying

In this research, the steady state and dynamic performances of two-lobe noncircular journal bearings with couple stress lubricant are presented. The lubricating oil, containing additives and contaminants, is modeled as the couple stress fluid. The modified Reynolds equation is obtained using the couple stress lubrication theory and is then solved by finite element method as an efficient numerical technique. The steady-state characteristics of bearings, including the load carrying capacity and attitude angle, are determined for various values of the couple stress parameter. The results show that applying the couple stress fluid improves the efficiency of two-lobe bearings in terms of an increased load carrying capacity and reduced attitude angle. Also, the stability performance of the investigated bearings is studied using rotor motion equations based on linear and nonlinear dynamic methods. The results indicate that any increase in the lubricant couple stress parameter enhances the bearing ability to damp the rotor perturbations. In other words, by varying the lubricant from Newtonian oil to the couple stress type and upgrading its properties, the curves of the critical mass parameter and whirl frequency ratio have an increasing and decreasing trend, respectively. Based on the fourth-order Runge–Kutta method results, the dynamic trajectory of the rotor center in the bearing space changes with increasing the couple stress parameter from diverging disturbances and limits the cycle perturbations around the bearing center to converging oscillations to the static equilibrium point. Moreover, the effect of changing lubricant properties on the two-lobe bearing’s performance is more pronounced at higher values of the couple stress parameter, especially with an increase in the noncircularity of bearings’ geometry.

On the Performance of Hybrid Foil-Magnetic Bearings

1999 ◽  
Vol 122 (1) ◽  
pp. 73-81 ◽  
Author(s):  
H. Heshmat ◽  
H. Ming Chen ◽  
J. F. Walton,
Keyword(s):  
Carrying Capacity ◽  
High Speed ◽  
Magnetic Bearing ◽  
Journal Bearings ◽  
Load Carrying Capacity ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Magnetic Elements ◽  
Load Carrying ◽  
Hybrid Bearing

Recent technological advancements make hybridization of the magnetic and foil bearings both possible and extremely attractive. Operation of the foil/magnetic bearing takes advantage of the strengths of each individual bearing while minimizing each other’s weaknesses. In this paper one possible hybrid foil and magnetic bearing arrangement is investigated and sample design and operating parameters are presented. One of the weaknesses of the foil bearings, like any hydrodynamic bearing, is that contact between the foil bearing and the shaft occurs at rest or at very low speeds and it has low load carrying capacity at low speeds. For high speed applications, AMBs are, however, vulnerable to rotor-bending or structural resonances that can easily saturate power amplifiers and make the control system unstable. Since the foil bearing is advantageous for high speed operation with a higher load carrying capacity, and the magnetic bearing is so in low speed range, it is a natural evolution to combine them into a hybrid bearing system thus utilizing the advantages of both. To take full advantage of the foil and magnetic elements comprising a hybrid bearing, it is imperative that the static and dynamic characteristics of each bearing be understood. This paper describes the development of a new analysis technique that was used to evaluate the performance of a class of gas-lubricated journal bearings. Unlike conventional approaches, the solution of the governing hydrodynamic equations dealing with compressible fluid is coupled with the structural resiliency of the bearing surfaces. The distribution of the fluid film thickness and pressures, as well as the shear stresses in a finite-width journal bearing, are computed. Using the Finite Element (FE) method, the membrane effect of an elastic top foil was evaluated and included in the overall analytical procedure. Influence coefficients were generated to address the elasticity effects of combined top foil and elastic foundation on the hydrodynamics of journal bearings, and were used to expedite the numerical solution. The overall program logic proved to be an efficient technique to deal with the complex structural compliance of various foil bearings. Parametric analysis was conducted to establish tabulated data for use in a hybrid foil/magnetic bearing design analysis. A load sharing control algorithm between the foil and magnetic elements is also discussed. [S0742-4795(00)01201-1]

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