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The purpose of this paper is to analyse the static performance characteristics of lobe journal bearings lubricated with a micropolar fluid, considering effect of non‐circularity. Number of lobes and their preload value are the non‐circularity parameters considered in the present study. The bearings undertaken for the investigation are two, three and four‐lobe symmetric journal bearings with finite width.

For this purpose, modified form of Reynolds equation is derived, based on Eringen's micropolar fluid theory and it is solved numerically using finite element method (FEM). The effect of the non‐circularity parameters of bearings on the steady‐state performance characteristics such as load carrying capacity, attitude angle, coefficient of friction and side leakage flow are presented and discussed.

The results show that the number of lobes and their preload value can influence the performance of lobe bearings. It is seen that, in order to provide certain improvement over simple cylindrical bearings, the non‐circularity parameters of lobe bearings must be chosen correctly. There is no single optimum profile for multi‐lobe bearing application.

Lobe bearings, compared with simple circular bearings, offer several geometric parameters to designers. These parameters must be chosen correctly, so that the requirements of a specific application can be fulfilled.

The purpose of this paper is to design and simulate a piezoelectric micropump using microelectromechanical systems technology for drug delivery applications.

Two piezoelectric actuators are used to actuate and bend the diaphragms in the proposed structure. In this micropump, the liquid flow is rectified by two silicon check valves.

The use of two piezoelectric transducer (PZT) actuators in the parallel mod not only reduces dead volume but also increases stroke volume as well. In addition to increasing the flow rate, this phenomenon enhances the operation of the micropump to have self-priming as smoothly as possible.

This actuating method results in a 22% increase in flow rate and compression ratio, as well as a 15% reduction in function voltage. The fluid-solid interaction is simulated using COMSOL Multiphysics 5.3a.

Variable geometry turbine (VGT), a key component of modern internal combustion engines (ICE) turbochargers, is increasingly used for better efficiency and reduced exhaust gas emissions. The aim of this study is the development of a new meanline FORTRAN code for accurate performance and loss assessment of VGTs under a wider operating range. This code is a useful alternative tool for engineers for fast design of VGT systems where higher efficiency and minimum loss are being required.

The proposed meanline code was applied to a variable geometry mixed flow turbine at different nozzle vane angles and under a wide range of rotational speed and the expansion ratio. The numerical methodology was validated through a comparison of the predicted performance to test data. The maps of the mass flow rate as well as the efficiency of the VGT system are discussed for different nozzle vane angles under a wide range of rotational speed. Based on the developed model, a breakdown loss analysis was carried out showing a significant effect of the nozzle vane angle on the loss distribution.

Results indicated that the nozzle angle of 70° has led to the maximum efficiency compared to the other investigated nozzle vane angles ranging from 30° up to 80°. The results showed that the passage loss was significantly reduced as the nozzle vane angle increases from 30° up to 70°.

This paper outlines a new meanline approach for variable geometry turbocharger turbines. The developed code presents the novelty of including the effect of the vane radii variation, due to the pivoting mechanism of the nozzle ring. The developed code can be generalized to either radial or mixed flow turbines with or without a VGT system.

The purpose of this study is to propose a fast method for predicting flow fields with periodic behavior with verification in the context of a radial turbine to meet the urgent requirement to effectively capture the unsteady flow characteristics in turbomachinery. Aiming at meeting the urgent requirement to effectively capture the unsteady flow characteristics in turbomachinery, a fast method for predicting flow fields with periodic behavior is proposed here, with verification in the context of a radial turbine (RT).

Sparsity-promoting dynamic mode decomposition is used to determine the dominant coherent structures of the unsteady flow for mode selection, and for flow-field prediction, the characteristic parameters including amplitude and frequency are predicted using one-dimensional Gaussian fitting with flow rate and two-dimensional triangulation-based cubic interpolation with both flow rate and rotation speed. The flow field can be rebuilt using the predicted characteristic parameters and the chosen model.

Under single flow-rate variation conditions, the turbine flow field can be recovered using the first seven modes and fitted amplitude modulus and frequency with less than 5% error in the pressure field and less than 9.7% error in the velocity field. For the operating conditions with concurrent flow-rate and rotation-speed fluctuations, the relative error in the anticipated pressure field is likewise within an acceptable range. Compared to traditional numerical simulations, the method requires a lot less time while maintaining the accuracy of the prediction.

It would be challenging and interesting work to extend the current method to nonlinear problems.

The method presented herein provides an effective solution for the fast prediction of unsteady flow fields in the design of turbomachinery.

A flow prediction method based on sparsity-promoting dynamic mode decomposition was proposed and applied into a RT to predict the flow field under various operating conditions (both rotation speed and flow rate change) with reasonable prediction accuracy. Compared with numerical calculations or experiments, the proposed method can greatly reduce time and resource consumption for flow field visualization at design stage. Most of the physics information of the unsteady flow was maintained by reconstructing the flow modes in the prediction method, which may contribute to a deeper understanding of physical mechanisms.

The work presented in this paper is concerned with mathematical modeling and experimental validation of mono-tube shock absorber. This paper aims to create damper model to predict accurately damping force, and experimental analysis is done by varying the various parameters, such as flow area in bleed(Ab), mass (M) and operating frequency(?).

Here, input is given in the form of sinusoidal excitation, and the output is received as a numerical data of the displacement transmissibility. These data are then processed to get the values of transmissibility and magnification factor for various frequency ratios. They are then plotted to have transmissibility and frequency response curves, as it is a generally accepted measure of how well the system is isolated from its surroundings.

It is better to have low transmissibility (larger bleed area), for lower suspension velocity, as it will reduce maximum acceleration transmitted to the sprung mass. However, for higher suspension velocity, bleed area should be low (higher transmissibility) to reduce displacement of tyre from road.

The development of faster vehicles and also the requirements of smoother and more comfortable rides have led to the fitment of dampers on almost on all present day vehicles. Shock absorbers have a significant influence on handling performance and riding comfort. Shock absorber plays an important role not only for comfort of the riders of the vehicle but also in the performance and life of the vehicle. However, no further reduction of vehicle vibration can be expected for using the optimum values of damping coefficient and spring stiffness for the shock absorber. Thus, it is necessary to make modification to improve the functions of shock absorber.

The purpose of this paper is to theoretically analyze an innovative form of variable bearing configuration having four pads with unique adjustability principle operated under journal misaligned conditions. The parameters such as load positions, degrees of misalignment (DM) and pad adjustment configurations influencing the steady-state performance of the four-pad adjustable bearing are detailed in this paper.

The proposed adjustable pad geometry possesses the ability to undergo radial and tilt motions in both inward and outward directions. Analysis is carried out by considering journal misalignment in vertical and horizontal planes with bearing modelled for load-on-pad and load-between-pad configurations. The film thickness equation derived to incorporate the radial and tilt adjustment parameters is further modified to accommodate the different load orientations and misaligned journal conditions. The pressure field equation is solved by applying finite-difference technique combined with Gauss Siedel iterative method.

At higher DM, peak pressures generated in the minimum film thickness region near the pad ends highly influences the bearing load carrying capacity. Results indicated that the adjustable four-pad bearing geometry is highly efficient in withstanding the journal misalignment by radially displacing and tilting the four pads in negative directions.

For bearing designers, this research highlights the importance of considering the misalignment factor during the design stages of an adjustable journal bearing. The proposed adjustability concept is proven to be effective enough to improve the bearing performance and, in turn, withstand the journal misalignment.

This study aims to investigate the performance characteristics of an externally adjustable bearing with multiple pads in steady state conditions. The proposed adjustable bearing geometry can effectively control the hydrodynamic operation in bearing clearances by adjusting the pads in radial and tilt directions. These pad adjustments have a significant role in improving the bearing characteristics such as load capacity, attitude angle, side leakage, friction variable and Sommerfeld number, which will be analysed in this paper.

The adjustable bearing is designed with circumferentially spaced four bearing pads subjected to similar radial and tilt adjustments. Tilt angles are applied along the leading edges of bearing pads. A modified film thickness equation is used to incorporate the pad adjustments and accurately predict the variation in film profile. Finite difference approximation is adopted to solve the Reynolds equation and discretize the fluid film domain.

For negative radial and tilt adjustments, higher hydrodynamic pressures are generated in bearing clearances, which increases the bearing load capacity at different eccentricity ratios. From comparative analysis for different pad adjustments, superior bearing performance is observed for bearing pads under negative radial and negative tilt adjustments.

This research presents a detailed theoretical approach to analyse the performance capability of a four pad adjustable bearing geometry, which is not available in literatures. Improved bearing performances with negative pad adjustments can attract bearing designers to implement the proposed adjustability-bearing concept in rotating machineries.

This paper aims to study the transient flow characteristics in a mixed-flow pump during the start-up period.

In this study, numerical calculation of the internal flow field in a mixed-flow pump using the sliding mesh method was carried out. The regulation of the pressure, streamline and the relative speed during the start-up period was analyzed.

The trend of the simulated head is consistent with the experimental results, and the calculated head is around 0.3 m higher than the experimental head when the rotation speed reached the stable stage, indicating that the numerical method for the start-up process simulation of the mixed-flow pump has a high accuracy. At the beginning, the velocity inside the impeller changes little along the radius direction and the flow rate increases slowly during the start-up process. As the rotation speed reached the stable stage, the flow inside the impeller became steady, the vortex reduced and transient effects disappeared gradually.

The study results have significant value for revealing the internal unsteady flow characteristics of the mixed-flow pump and providing the reference for the design optimization of the mixed-flow pump.

PROMINENT among hydraulic servos today are those being developed in the aeronautical field, both for conventional aircraft and for guided missiles. In general these applications demand the following characteristics of the servos:

This study aims to investigate the impact of surface waviness on the static performance parameters of hydrodynamic journal bearings operating with lubricants containing copper oxide (CuO) and cerium oxide (CeO₂) nanoparticles.

The static performance parameters of bearings with surface waviness and the addition of nanoparticles in lubricants were calculated using the nondimensional form of Reynolds equation and finite element method. Static performance parameters are calculated at different waviness numbers in the circumferential, axial and both directions at various wave amplitudes with variable viscosities of lubricants with nanoparticles using the viscosity equation forming a relationship between the relative viscosity, temperature and weight fraction of nanoparticles in lubricant developed from the experimental results.

The computed results indicate that the impact of waviness on the bearing surface enhances the load capacity, reduces friction coefficient, and is more effective in the circumferential direction than in the axial direction or in both directions. The addition of CuO and CeO₂ to the lubricant enhanced its viscosity which further improved the steady-state parameters of the wave bearing.

This study is based on a numerical technique, which has significant limitations, and the simulated results must be tested experimentally.

The current findings will be beneficial for designers to improve the performance of hydrodynamic journal bearings.

The calculated results demonstrate that the combined effect of the surface waviness on bearings and the addition of nanoparticles to lubricants can greatly increase the performance of hydrodynamic journal bearings.