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This paper seeks to present some new designs of sliding bearings lubricated with magnetic fluids (ferrofluids) and the possibility of using them in modern bearing technology, in new computer and audiovisual equipment among others.

The paper presents new designs of journal, thrust and journal‐thrust sliding bearings lubricated and sealed with magnetic fluids such as: magnetic fluid bearing bushing made of magnetizable material, pivot bearings with porous sleeve impregnated with ferrofluid, self‐aligning bearings, hydrodynamic ferrofluid bearings with spiral and herringbone grooves structure are presented. Moreover, examples are shown of applications in modern bearing technology.

The paper provides information about new designs of magnetic fluid sliding bearings assemblies and gives the main advantages of these bearings over conventional ball bearings, such as extremely low non‐repetitive run‐out (high‐accuracy of rotation), good damping and quietness of operation, maintenance free service and high reliability.

This paper offers some new designs of compact, low friction and self‐contained magnetic fluid sliding bearings and points up their practical applications.

In this paper, a computational model of a coaxial magnetic gear (MG) design with viscose ferrofluid between rotors is proposed. Viscose ferrofluid is used to decrease the magnetic reluctance and therefore creates higher magnetic torque. However, viscose friction of ferrofluid is undesirable and must be minimised in this particular application. MG is supposed to operate under low rotational speeds, where the dynamic viscose friction is very low, and the effects of the viscose ferrofluid over the MG’s efficiency must be estimated. The paper aims to analyze the performance of MG with viscose ferrofluid and to estimate the MG efficiency by computational model using finite element method (FEM).

An MG design with viscose ferrofluid between the outer low-speed rotor and modulating steel segments was modelled as a coupled transient magnetic field problem and a kinematic model with viscous friction coefficients derived from a previously computed fluid dynamics model.

The proposed computational implementation is suitable for homogeneous magnetic fluid modelling in electromagnetic actuators and rotational machines. The results regarding power and torque transmission of MG were obtained by coupled finite element modelling. The efficiency of MG significantly decreased due to ferrofluid friction.

The described MG design with viscose ferrofluid is a novel device with new operational characteristics, and new results for the effects of viscose ferrofluid friction in the outer magnetic field over the MG efficiency are estimated.

The purpose of this study is to investigate the hydrodynamic lubrication characteristics of ferrofluid film for spiral groove mechanical seal in external electromagnetic field and to analyze the effects of the volume fraction of ferrofluid, parameters of the electromagnetic field, operating parameters and geometrical parameters of mechanical seal on the characteristics of ferrofluid film.

The relationship between the ferrofluid viscosity and the intensity of external electromagnetic field was established. Based on the Muijderman narrow groove theory, the pressure distribution was calculated with the trial method by trapezoid formula.

It was found that pressure, average viscosity, average density and opening force of ferrofluid between end faces increase with the increase in intensity of current, volume fraction of ferrofluid, rotating speed, pressure differential and spiral angle; decrease with the increase in temperature; and increase at first and then decrease with the increase in the ratio of groove width to weir and the groove length. All of them reach the maximum value when the ratio of width of groove to weir is 0.7 and the ratio of groove length is 0.6. Leakage of ferrofluid increases with an increase in intensity of current, volume fraction of ferrofluid, rotating speed, pressure differential, spiral angle and ratio of groove length; decreases with an increase in temperature; and increases at first and then decreases with the increase in the ratio of groove width to weir. The tendencies of characteristics of silicone oil are consistent with those of ferrofluid, and the characteristics of silicone oil are smaller than those of ferrofluid under the same condition.

The volume fraction of ferrofluid, rotating speed, spiral angle, ratio of groove width to weir, groove length and temperature have a significant influence on the characteristics of ferrofluid film; however, intensity of current and the pressure differential have slight influence on the characteristics of ferrofluid film. An analytical method for analyzing hydrodynamic lubrication characteristics of ferrofluid film in a spiral groove mechanical seal was proposed based on the Muijderman narrow groove theory.

This paper aims to investigate the performance of a ferrofluid-based hydrodynamic journal bearing system.

This paper presents a new design of ferrofluid-based hydrodynamic journal bearing. An experimental set-up consisting of a magnetic shaft along with a brass bearing was modified and developed. A permanent magnet was used to make the selected shaft material magnetic. The load and speed were varied to conduct the analyses for different test conditions.

The paper provides information about a design of ferrofluid-based journal bearing and its improved performances. For moderate to higher loads at different shaft speeds, it was found that because of the magnetization effect, the maximum film pressure in case of a ferrofluid lubricant increased up to approximately 60 per cent, compared with that of the conventional lubricant-based journal bearing system. Besides, the temperature rise was found smaller for ferrofluid lubricants, thus making the system cooler while running.

This paper offers a new design of magnetic bearing system for the experimental analysis by utilizing a magnetic shaft with a non-magnetic bearing. The present ferrofluid-based bearing design is less complicated from manufacturing point of view.

First, the effect of magnetic field intensity and nano-ferrofluid concentrations on surface roughness was evaluated in magnetic minimum quantity lubrication (MMQL). Then, the effect of lubricant flow rate and nozzle position on surface roughness was investigated in MQL, MMQL, electrostatic MQL (EMQL) and electromagnetic MQL (EMMQL).

This study examined the performance of MQL under magnetic and electric fields in turning AISI 304 stainless steel in terms of surface roughness and compared the results with those obtained from wet cutting and MQL turning operations. To prepare the nano-ferrofluid used in different states of MQL, Fe₃O₄ nanoparticles were added to the base fluid.

The results showed that the surface roughness under the EMMQL technique decreased by 36% and 49.4% on average compared with wet and MQL techniques, respectively. The lubrication technique affected the surface roughness by 90.2%, whereas it was 8.3% for the lubricant flow rate. EMQL and EMMQL techniques had no significant difference in their effects on surface roughness. In the innovative MMQL technique, the nano-ferrofluid concentration of 6% and magnetic field intensity of 93 G resulted in lower surface roughness of the workpiece relative to other counterparts.

Examining previously published studies showed that using nano-ferrofluids under a magnetic field for cooling purposes in machining processes have less considered by researchers. This study applies an innovative method of lubrication under the concurrent effect of magnetic and electric fields, called EMMQL, to improve the efficiency of MQL in machining hard-to-cut materials. For comprehensively inspecting the newly presented method, the effects of several parameters, including the nano-ferrofluid concentration, magnetic field intensity, lubricant flow rate and position of lubricant spray nozzle, on the surface roughness of workpiece in turning of AISI 304 stainless steel are investigated.

The purpose of this paper is to investigate the dynamic characteristics of exponential slider bearings lubricated with a ferrofluid. Because of the development of modern engineering, the increasing use of ferrofluids in lubrication fields has shown great importance. Understanding the dynamic characteristics of exponential film bearings is helpful for engineers in bearing selection.

Applying the Shliomis ferrohydrodynamic flow model and considering the squeezing action of bearing pads, a dynamic Reynolds equation is obtained for an exponential film slider bearing lubricated with a ferrofluid in the presence of a transverse magnetic field. Analytical solutions of dynamic characteristics are obtained.

According to the results, the ferrofluid-lubricated exponential film bearing provides better dynamic stiffness and damping characteristics than the non-ferrofluid ones, especially the bearing operating at higher values of the volume concentration parameter and the magnetic Langevin parameter.

Numerical tables of stiffness and damping coefficients for different values of the volume concentration parameter and the Langevin parameter are also included for engineering references.

This paper aims to study the inertia squeeze film characteristics between ferrofluid-lubricated circular stepped disks. Owing to the development of modern machine systems, the application of ferrofluids has received great attention. Because the circular disks are a special situation of circular stepped squeeze films, a further study of fluid inertia force effects on the ferrofluid-lubricated circular stepped squeezing mechanism is motivated.

On the basis of the ferrohydrodynamic flow model of Shliomis incorporating the momentum integral method, the effects of fluid inertia forces in ferrofluid-lubricated circular stepped squeeze films in the presence of external magnetic fields are investigated in this study. Analytical solutions of squeeze film performances are derived.

The fluid inertia force effects provide an increased load capacity and a longer squeeze film time for the ferrofluid-lubricated circular stepped squeeze film, especially for a larger value of the inertia parameter, the Langevin parameter and the volume concentration and a smaller value of the radius ratio and the step height ratio.

For engineering applications, numerical tables for squeeze film loads of circular stepped disks are also provided in this paper.

This paper aims to analyze the accuracy of the single and two-phase numerical methods for calculation of ferrofluid convective heat transfer in the presence of a magnetic field. The findings of current study are compared with previous single-phase numerical results and experimental data. Accordingly, the effect of various parameters including nanoparticles concentration, Reynolds number and magnetic field strength on the performance of the single and two-phase models are evaluated.

A two-phase mixture numerical study is carried out to investigate the influence of four U-shaped electromagnets on the hydrodynamic and thermal characteristics of Fe₃O₄/Water ferrofluid flowing inside a heated channel.

It is observed that the applied external magnetic field signifies the convective heat transfer from the channel surface, despite local reduction at a few locations. The maximum heat transfer enhancement is predicted as 23% and 25% using single and two-phase models, respectively. The difference between the results of the two models is mainly attributed to the slip velocity effect which is accounted for in the two-phase model. The magnetic field gradient leads to a significant increase in the slip velocity which in turn causes a slight difference in velocity and temperature profiles obtained by the single and two-phase models in the magnetic field region. According to percentage error calculation, the two-phase method is generally more accurate than the single-phase method. However, the percentage error of both models improves by decreasing either magnetic field intensity or Reynolds number.

For the first time in the literature, to the best of the authors’ knowledge, the current work analyzes the accuracy of the single and two phase numerical methods for calculation of ferrofluid convective heat transfer in the presence of a magnetic field.

Ferrofluid seals are known for their low friction torque and high tightness. However, they have some limitation due to the allowable rotational speed. The work presented here analyzes the performance of newly designed seals which are a combination of a ferrofluid and a centrifugal seal. The new seals can operate at high speeds. The purpose of this study is to theoretically predict the performance of combined seals.

Three seals were designed and selected for analysis. A version of the seals with a nonmagnetic insert is also considered, the purpose of which is to facilitate the installation and return of ferrofluid during low rotational speeds. The analyses were based on combining the results of numerical simulation of magnetic field distribution with mathematical models.

A combination of ferrofluid sealing and centrifugal sealing is possible. Analyses showed that the combined seal could hold a minimum pressure of 190 kPa in the velocity range of 0–100 m/s. The problem with this type of seal is the temperature.

New seal designs are presented. Key parameters that affect the seal operation are discussed. A methodology that can be used in the design of such seals is presented.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2023-0221/.

This study aims to investigate the combined effects of roughness and ferrofluid lubricant on finite journal bearing load capacity and squeeze time.

The stochastic theory of Christensen is applied to study the surface roughness effect. The Shliomis model is used to take into account the effects of the rotational viscosity of ferromagnetic particles and their magnetic moment. A finite wire located in the center of the shaft produces the applied magnetic field. A developed computing code allows predicting the effect of the surface roughness on the performance of the considered journal bearing. The good agreement with the results of the literature validates the used approach.

This study shows that unlike longitudinal roughness, the presence of transverse roughness makes the use of ferrofluid more beneficial in terms of increasing the performance of finite journal bearings. This increase is more significant for large relative eccentricities, which present an ideal confinement.

This study shows the effect of two surface roughness patterns on the squeezing performance of a finite journal bearing lubricated by a ferrofluid.