Hybrid journal bearings are widely employed in high-speed applications due to their superior load-carrying capacity and improved stability compared to conventional journal bearings. The dynamic performance of such bearings can be further enhanced by incorporating an asymmetric hybrid hole-entry configuration in conjunction with surface roughness effects. In the present study, the Reynolds equation governing Micropolar lubrication in a journal bearing system is modified to account for surface roughness and is solved using the finite element method coupled with the constant-flow valve restrictor equation. Numerical results are presented for a prescribed applied load W & strns; o = 1.5 , a concentric design pressure ratio ( beta * = 0.5 ) , and a variance ratio V & strns; r j = 0.5 under hybrid operating conditions. Bearing performance characteristics are evaluated for surface roughness parameters in the range Lambda = 4 - 10 , considering different roughness orientations (gamma), and for Micropolar lubricant parameters N 2 = 0.5 , 0.9 and l m = 10 , 30 . The results reveal significant improvements in dynamic coefficients when a longitudinally roughened bearing operates with a Micropolar lubricant. Compared to a smooth bearing lubricated with a Newtonian fluid, increases of up to 53.77% and 46.5% are observed in the stiffness coefficients, while enhancements of up to 34.11% and 35.63% are achieved in the damping coefficients of the fluid film.

This article investigates the synergistic effect of surface texturing and Magneto-rheological (MR) lubricants on the steady-state and dynamic performance indices of two-lobe journal bearings. MR lubricants, composed of magnetic particles in mineral oil, offer tunable viscosity through applied magnetic fields. The study employs a generalised Reynolds equation, incorporating a continuous Bingham fluid model to capture the lubricant's non-linear behaviour. The Dave model has been used to describe the shear stress of commercially available MRF122EG lubricant, as a function of volume fraction of magnetic particles and magnetic field. Surface textures, comprising arrays of spherical and conical cap dimples in various circumferential configurations, are analysed. The Reynolds equation is solved using a finite element approach coupled with the Newton-Raphson method, and a mass-conserving algorithm addresses gaseous cavitation. Optimal surface texture configurations for maximising direct stiffness parameters are determined, revealing that partial texturing in the first half of the bearing is most effective. The study further examines the influence of dimple shape, texture configuration and MR lubricant on the performance of circular and two-lobe journal bearings. Journal center trajectories are predicted by solving the equation of motion using the fourth-order Runge-Kutta method. The key findings indicate that the combined application of MR lubricant and partial surface texturing in the first half of two-lobe bearings enhances direct stiffness parameters by up to 781.9%. Threshold speed, a critical design parameter, is significantly improved (89.3%) in two-lobe bearings through surface texturing and MR effects. Two-lobe journal bearings with MR lubricants exhibit smaller and more stable journal center trajectories and limit cycles, indicating enhanced dynamic stability. Consequently, for applications requiring enhanced stability and performance, first half partially textured surface two-lobe journal bearings with MR lubricants should be preferred.

In the present study, the combined influence of surface roughness and Micropolar lubricants on the performance of a hole-entry type hybrid journal bearing is investigated. The Reynolds equation governing Micropolar lubrication for the journal bearing system is suitably modified to incorporate the effects of surface roughness. The resulting governing equations are solved by coupling the capillary restrictor flow equation with a finite element formulation. Different magnitudes of surface roughness and Micropolar lubricant parameters are considered for various surface roughness patterns in order to comprehensively evaluate their impact on the bearing performance characteristics. The analysis demonstrates that surface roughness, when used in conjunction with Micropolar lubricants, significantly alters the hydrodynamic behavior of the bearing. Specifically, the results reveal an 18.9% reduction in bearing flow rate, a 5% increase in the minimum fluid film thickness, and a pronounced enhancement in the stiffness and damping coefficients for a bearing with a longitudinal surface roughness pattern operating under Micropolar lubrication, compared to an equivalent smooth bearing lubricated with a Newtonian fluid. These findings highlight the potential advantages of employing Micropolar lubricants and engineered surface textures in improving the dynamic and load-carrying performance of hybrid journal bearings.

This study deals with the finite element method-based simulations of a textured surface, two-lobe journal bearing operating with a magnetorheological (MR) lubricant-a smart fluid composed of fine magnetic particles suspended in a carrier fluid. The flow of the MR lubricant within the textured bearing, which incorporates rectangular micro-grooves along axial directions, is modeled using Reynolds' equation. The Bingham plastic model defines the MR fluid's viscosity, accounting for the influence of yield stress, magnetic field, and shear-strain rate. The Reynolds equation is solved using the finite element method to determine film pressure, film direct stiffness coefficients, threshold speed, journal trajectories and limit cycles. A Multi-Objective Genetic Algorithm (MOGA) is used to optimize rectangular micro-groove attributes (i.e., number, width, depth and length) to maximize the direct film stiffness coefficients and threshold speed of stability. A robust design recommendation is proposed based on Fuzzy-based Multi-Objective Genetic Algorithm (Fuzzy-MOGA) optimization, targeting improved film stiffness coefficients and threshold speed. The results exhibit a stable and resilient optimization landscape, with minimal sensitivity to input variations. The numerical results demonstrate that the combined use of MR lubricant, two-lobe geometry and surface texturing enhances stiffness coefficients (116.7%similar to 850.8%) and threshold speed (81.3%). The two-lobe bearing with partial surface texturing in the leading half demonstrates the highest dynamic stability, as evidenced by threshold speed, minimal journal center trajectories and compact limit cycles.

Purpose This study aims to investigate effectiveness of surface texturing in improving steady-state and dynamic performance characteristics of two-lobe journal bearings using electrorheological (ER) lubricants. Design/methodology/approach The Reynolds equation is solved using finite element approach and Newton–Raphson method, with gaseous cavitation in lubricant addressed via a mass-conserving algorithm. The ER fluids constitute dielectric particles suspended in non-conductive oil. A continuous Bingham fluid model describes lubricant’s non-linear behavior. The study explored how dimple shape, surface texture configuration and applied electric field affect performance of two-lobe journal bearings. To assess the journal’s dynamic stability, equation of motion is solved using fourth-order Runge–Kutta method, predicting the journal’s center trajectory. Findings The findings reveal that applying ER lubricants and partial surface texturing in two-lobe journal bearings boosts direct stiffness by 1037.1% and damping by 46%. In addition, the threshold speed improves by 100.1%, and the bearings exhibit smaller, more stable linear motion trajectories and limit cycles. These results suggest that designers should consider using first-half textured surface two-lobe journal bearings operating with ER lubricants to enhance stability and performance under simulated conditions. Originality/value This study presents rotor-dynamic performance of textured surface two-lobe journal bearing operating with ER lubricant. Texture shape, attributes and configuration are determined to maximize direct stiffness coefficients and minimize the journal center motion trajectories. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-12-2024-0458/

The piston is a critical component of an engine, subjected to cyclic gas pressure and inertial forces during operation. These conditions expose the piston to various fatigue-induced wear such as side wear, piston head cracks, etc. Thus, it is essential for the designer to consider both dimensional and material aspects in the design considerations concerning a piston. This paper describes the procedural framework for designing a piston of a four-stroke engine. A systematic optimization of the same has been done by utilizing on three different materials. Conventionally, the piston is usually made of aluminium alloy, but this paper explores the possibility of using gray cast iron and aluminum silicon carbide composite. It involves modelling on SpaceClaim with further investigations on ANSYS Workbench. The model is analysed on thermal and static loading conditions and the results of the same are recorded numerically and graphically. The validation of the model developed is done by convergence and grid independence. Comparison between the experimental and the standard values are also done to ensure the accuracy of present model for further analysis.

Air journal bearings are generally employed in the ultra-high-speed machinery and robotics because of their high values of stiffness and damping coefficients. The current work deals with the numerical analysis of misaligned two-lobe air journal bearings. By using the finite element formulation, nonlinear Reynolds equation for compressible air as a lubricant has been solved for computing the characteristics of misaligned air bearing. The coefficients for stiffness and damping of film of air have been computed for misaligned two-lobe air journal bearing. The effect of misalignment on these coefficients has been found significant. Analytically calculated results also show that the misalignment in air bearing significantly drops its air-film thickness. However, the misalignment increases the air bearing stability and critical speed of bearing.

This study investigates the effectiveness of surface texturing for enhancing steady-state and dynamic performance of three-lobe journal bearings using electrorheological (ER) lubricants. ER fluids consist of dielectric particles suspended in non-conductive oil. The fluid flow in bearing clearance is modeled by generalized Reynolds equation. The non-linear characteristics of lubricant are captured using continuous Bingham fluid model. Surface textures are designed with arrays of spherical and conical dimples arranged in various circumferential configurations. The Reynolds equation is solved using finite element approach and Newton-Raphson method, incorporating a mass-conserving algorithm to address gaseous cavitation in film. Different surface texture configurations are analysed to maximize bearing's direct stiffness parameters. The findings indicate that partial texturing in first half of the bearing maximizes these stiffness parameters. The study further examines impact of dimple shape, surface texture configuration, and applied electric field on the performance of circular and three-lobe journal bearings. The equation of motion for journal is solved using fourth-order Runge-Kutta method to predict journal's center trajectories. The application of ER lubricant and partial surface texturing in three-lobe journal bearing enhances direct stiffness parameter by 339.3% and increases damping parameter by 43%. The threshold speed, a crucial design factor for journal bearings is significantly improved (72.8%) through surface texturing and ER effect in three-lobe bearings. Moreover, three-lobe journal bearings utilizing ER lubricants demonstrate smaller and more stable linear motion trajectories of journal. Under simulated conditions, designers should consider textured surface three-lobe journal bearings with ER lubricants for enhanced stability and performance.

This study is conducted to investigate the effect of ER lubricant on the bearing performance characteristics. The numerical solution of Reynold’s equation has been presented using the finite element technique. Fluid’s Non-Newtonian behaviour has been modelled using the Bingham model and JFO boundary conditions have been applied to solve the problem of cavitation in the journal bearing. Two-lobe shape journal bearing resulted in better stiffness and damping characteristics as compared to the traditional bearing design. The ER fluid shows very promising results in improving the bearing performance parameters for the design of the two-lobe bearing. The stability analysis is performed by considering Routh’s criteria. The two-lobe bearing configuration gave higher values for marginal threshold speed.

PurposeAn electrorheological (ER) fluid consists of dielectric particles blended in a nonconducting oil. ER lubricants are often considered smart lubricants. This paper aims to examine the steady state and dynamic response of multilobe journal bearings using an ER lubricant.Design/methodology/approachReynold's equation has been used to describe the lubricant flow in the journal-bearing clearance space. The Bingham model is used to characterize the nonlinear behavior of the lubricant. The solution of the Reynolds equation is obtained using the Newton-Raphson method, with gaseous cavitation in the fluid film numerically addressed by applying a mass-conserving algorithm. The effects of lobe geometry and the applied electric field are investigated on film pressure profile, fluid film thickness, direct stiffness and damping parameters. The equation of motion for journal center coordinates is solved using the fourth-order Runge-Kutta method, to predict journal center motion trajectories.FindingsUsing ER lubricant combined with two-lobe journal bearing significantly improved the minimum film thickness by 49.75%, the direct stiffness parameter by 132.18% and the damping parameter by 206.3%. However, the multilobe configuration was found to negatively impact the frictional powerloss of the bearing system. In the case of multilobe configurations of journal bearings using ER lubricant, linear motion journal trajectories are observed to be reduced and exhibit increased stability.Originality/valueThis study presents the effect of an ER lubricant and multilobe configuration on the rotor-dynamic performance and stability analysis of hydrodynamic journal bearings.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-06-2024-0201/

The crankshaft plays a pivotal role in ensuring the internal combustion engine’s efficiency and precision. To enhance its design parameters, an optimized crankshaft is proposed. Through computer simulations, two different materials (grey cast iron and cast iron ENGJL100) are selected for the crankshaft, and their equivalent stress, total deformation, equivalent elastic strain, and directional deformation are computed. This paper focuses on analysing the materials used for the engine's crankshaft and conducting structural strength tests in accordance with specific requirements. The crankshaft model is developed using SolidWorks 2018 software. The study concludes that grey cast iron ENGJL100 is a suitable material for the crankshaft, exhibiting superior strength and durability when placed in the designated location within the design.

The hydrodynamic journal bearing is a crucial machine element used to support radial load in turbomachines. The research in journal bearings focuses on enhancing the steady state and dynamic performance indices. This study deals with the CFD simulations of hydrodynamic journal bearing operating with non-Newtonian lubricants. The CFD simulations have been performed using the Fluent module of Ansys 2023. The Power law fluid model has been used to describe the non-Newtonian character of the lubricant. The plots are generated for maximum fluid pressure, film pressure distribution, and turbulence dissipation for the Newtonian, pseudoplastic, and Dilatant nature of lubricant. Insights into fluid film pressure distribution and turbulence dissipation rates inform guiding designers for improved performance. Understanding maximum pressure trends is vital for design assessment, preventing failures, and optimizing the durability of the hydrodynamic journal bearings. Practical applications for machine designers include a comprehensive understanding of design parameters’ impact on performance, ensuring reliability in turbomachines. Overall, the research contributes to the field, offering academic and simulation insights of a hydrodynamic journal bearing.

An Electro-rheological (ER) fluid comprises dielectric particles blended in a non-conducting oil. The ER lubricants are commonly known as smart lubricants. This study utilizes an ER lubricant to examine the static and dynamic response of multi-lobe journal bearing. The lubricant flow within the journal-bearing clearance space is described by Reynold’s equation, while the non-linear behavior of the lubricant is characterized using the Bingham model. The solution of the Reynolds equation is obtained employing the Newton-Raphson method, with numerical addressing of gaseous cavitation in the fluid film through a mass-conserving algorithm. The effects of lobe geometry and the applied electric field are scrutinized on bearing performance metrics. The equation of motion for the journal is solved utilizing the fourth-order Runge-Kutta method to predict journal center locus/trajectories. The utilization of ER lubricant in conjunction with a two-lobe journal bearing notably enhances the minimum film thickness by 63.5%, the direct stiffness parameter by 182.4%, and the damping parameter by 210.14%. The multi-lobe configuration adversely affects the frictional power loss of the bearing system. The threshold speed, a critical parameter in the design and operation of journal bearings, is improved by the ER effect and is higher for multi-lobe bearings. In multi-lobe configurations of journal bearings operating with ER lubricant, linear motion journal trajectories are noted to be smaller and more stable. Under given operating conditions, designers should prioritize two-lobe journal bearings operating with ER lubricants, as they exhibit greater stability and superior performance metrics in both steady-state and dynamic conditions.

This article deals with the steady and dynamic performance analysis of rough surface circular and multi-lobe journal bearings operating with non-Newtonian lubricant in turbulent regimes. The numerical solution of Reynold's equation was obtained using the finite element method. To account for surface roughness, the Patir and Cheng model was used, and fluid turbulent behavior was modeled using the turbulent theory as proposed by Ng and Pan. The non-Newtonian behavior of the lubricant is presented by the Rabinowitsch fluid model, and JFO boundary conditions are used to solve Reynold's equation, considering gaseous cavitation. The bearing with micro-roughness has been considered in numerical analysis and transverse roughness has been reported to improve bearing performance indices. Among the different bearing design configurations, the two-lobe bearing configuration provides significantly improves the minimum film thickness, hydrodynamic pressure, and dynamic parameters. The presence of turbulent flow and transverse surface roughness produces a synergistic effect that enhances the minimum film thickness, stiffness, and damping parameters of journal bearings. This study provides a detailed comparison between various bearing designs and recommends the use of two-lobe bearings for high-speed applications.

The functionality of an engine relies on the efficient working of its piston. The piston is always acted upon by cyclic stresses and dynamic loads which directly affects its performance. Therefore, it is imperative to study its static and modal characteristics. The present study has been carried out to analyse the natural frequencies of vibration of a mechanical piston. The piston model used in the study has been modelled for two different aluminium alloys AA6105 and A7075-T6. Honda Activa 110 cc BS-IV Engine has been used for standard piston dimensions. Finite element analysis solver ANSYS has been used to perform static structural analyses. The equivalent stress, shear stress, and deformation in the solid model of the piston were obtained for two different aluminium alloys. The von Mises stress is computed as 163.87 MPa and 157.75 MPa for AA6105 and A7075-T6, respectively, which were below the yield value of the material. Six vibration modes were computed by performing modal analysis on piston considering both the aluminium alloy materials. The lowest natural frequencies reported for AA6105 and A7075-T6 were 8320.8 Hz and 8185.6 Hz, respectively. The piston skirt shows maximum deformation under different modes of natural frequencies. The solid model showed improvement in static and dynamic capabilities of a piston. Findings of this study will serve as a reference and framework for piston design.

This article concerns with the numerical simulations of textured surface hybrid thrust bearings operating with Electro-rheological (ER) lubricant. An ER fluid comprises dielectric particles suspended in an insulating viscous medium. Electrorheological (ER) lubricants are considered smart lubricants. Reynold's equation is used to model the flow of an ER lubricant in textured surface thrust bearings. The texture is provided as hemispherical, cylindrical, elliptical, and square shape micro-depression oriented along the circumferential and radial direction. The Patir and Cheng model is used to describe micro-roughness on a thrust pad. The continuous Bingham model is used to define the viscosity of the ER lubricant in terms of yielding stress, electric field, and shear-strain rate. The Reynolds equation is solved by applying the finite element method to obtain film pressure, load-supporting capacity, frictional power loss, film stiffness, and damping parameters. The texture shapes are optimized for dimple size, depth, and length for getting maximum load-supporting capacity and stiffness coefficient, and minimum frictional power loss. The numerical results predicted an enhancement in the load-supporting capacity (+257.3%) and film stiffness parameters (+323.2%) owing to the synergistic use of ER lubricant and optimized geometric parameters of square/elliptical dimples. The frictional power loss was reported to reduce significantly (−48.8%) by the use of micro-dimples. The application of ER lubricant was also found to slightly enhance (+4.3%) the frictional power loss in textured bearings. The transverse surface roughness vis-à-vis smooth surface is observed to improve the load-supporting capacity, stiffness, and damping parameters of textured surface bearings.

This paper concerns with the numerical simulations of hydrodynamic journal bearing. Influence of number of lobes has been examined on the steady and dynamic performance parameters of bearing system. Finite Element (FE) formulation is carried out to perform numerical simulations of bearing system. The performance of circular and multi-lobe (2–4 lobe) journal bearings have been computed and compared for film pressure distribution, min. film thickness, rotor-dynamic coefficients, etc. These performance indices are obtained for a wider range of external load. It has been found that a two-lobe journal bearing offers better steady and dynamic performance as to circular and multi-lobe journal bearing configurations. It is observed that a two-lobe journal bearing vis-a-vis circular bearing significantly enhances the minimum film thickness and direct stiffness coefficients, and marginally reduces the threshold stability margin.