Journal of The Brazilian Society of Mechanical Sciences and Engineering最新文献

Improving wind generator performance demands advanced and efficient control strategies to maximize aerodynamic energy conversion. Since the wind is always changing, the output power of a wind generator may be maximized by driving the wind rotor at the best rotational velocity for a given wind velocity. This is accomplished using a maximum power point tracking (MPPT) system. Over the years, many advanced MPPT controls have been developed, each with huge potential to generate the maximum power in the most efficient and effective way. Concerning the present study on the MPPT control, this paper discusses the analysis, design and real-time implementation of a new intelligent cooperative control technique to enhance the MPPT of wind power generators with isolated loads. The primary goal of the research is to develop of an interval type-2 fuzzy logic system (IT2-FLS) MPP estimator that can ensure the operation of the wind generator in maximum power with higher efficiency, less steady-state error, and power fluctuation. Furthermore, a fractional nonlinear synergetic controller has also been designed to enhance the speed response, which can be implemented with a DC–DC boost converter. The suggested intelligent cooperative MPPT controller is tested in an experiment using a permanent magnet synchronous generator-based wind turbine structure. Two different wind speed test scenarios were performed to evaluate the performance of the considered strategy, where the performance of the suggested intelligent cooperative MPPT controller was compared to the performance of the IT1-FLS-based MPPT technique in terms of speed fluctuation ratio, speed error in steady state, and tracking reference. The obtained results indicate that the suggested intelligent cooperative MPPT controller achieves superior performance. The effectiveness of the considered strategy is very good, which makes it a suitable option for regulating various wind generators.

The present study concentrates on the flow of 2 immiscible fluids through space between 2 coaxial cylinders filled with 2 different layers of anisotropic porous mediums. The inner cylinder is impermeable, and we assumed that its surface is slippery. The permeability of both porous regions is different and depends on anisotropic parameters. The flow in porous regions is due to the applied pressure gradient and the movement of the outer cylinder in the axial direction with a constant speed. Velocity profiles of Couette flow, Poiseuille flow, and Couette-Poiseuille of the present problem are analytically obtained using appropriate boundary conditions. Further, the impacts of anisotropic parameters and other physical parameters are studied and graphically presented. It is found that increasing permeability ratio and anisotropic angles have increasing and decreasing impacts on velocity profiles, respectively and strongly influence the skin friction. In the no-slip case, there is greater skin friction on the surface of the inner cylinder than in the slip case. We found that a difference in the viscosities slows the velocity of the fluids, but a slippery surface enhances the velocity. Current findings about anisotropic permeability, viscosity ratio, and slip are used to study the flow mechanism in various industrial and engineering problems involving artificial porous materials.

The present work investigates the transonic flow past a 2D circular cylinder using the dynamic mode decomposition (DMD) method. The DMD is a data-driven tool for the analysis and characterisation of dynamic systems that identifies coherent structures (or modes) in the data with corresponding frequencies and rates of growth. Numerical simulations using the Euler equations for compressible flows are done considering Mach numbers 0.5 and 0.75. In the first case, the flow is periodic and acoustic oscillations are synchronised with the vortex shedding, while in the second case it presents more complex structures with shock waves. The DMD revealed that the cylinder emits noise similarly to an acoustic dipole, and captured the fundamental Strouhal number for the flow in both cases. Additionally, the DMD modes were used to reconstruct the data set. The reconstruction was able to describe well the time series for a Mach number of 0.5, but there was a significant error for Mach 0.75. The Sound Pressure Level field was also reconstructed, and the maximum error for Mach 0.5 was around 1 dB, while for Mach 0.75 was 18 dB.

In order to improve corrosion resistance of structural elements, stainless-steel coatings can be employed thus allowing a relatively low-cost carbon steel substrate to be protected against potentially hazardous environments. In the present work, austenitic stainless-steel coatings were produced by friction surfacing, with constant horizontal (190 mm/min) and vertical (95 mm/min) feed rates and rotation speed values of 1300, 1500, 1700, 1900 and 2100 rpm. The average dynamically recrystallized grain size (d_DRX) on the coatings surface was determined by optical microscopy as a function of deposition conditions, allowing subsequent correlations with different parameters obtained from potentiodynamic polarization scans and electrochemical impedance spectroscopy analyses in 0.5 M H₂SO₄ and 0.6 M NaCl to be investigated. EDX analyses were performed along the thickness of coatings to evaluate possible variations in the (Cr, Ni and Mo) contents of mechtrode material (alloy 316L), and it was possible notice that the increase in rotation speed contributed to producing a coating with more homogeneous chemical composition. In both investigated electrolytes, the variation of rotation speed did not significantly influence the corrosion resistance of the deposited coatings, evidencing that the friction surfacing process delivers stable output in terms of electrochemical performance even when varying parameters over a relatively wide range (1300–2100 rpm rotation speed).

Research has been conducted on the material trends and manufacturing characteristics of the drive motor, which is one of the three core technologies of electric vehicles. To develop high-efficiency and vibration-free motors, automobile manufacturers are considering various design changes, material modifications, and alterations in manufacturing methods for the drive motor. Typically, the drive motor core is stacked using 0.25–0.3t steel plates in both emboss-type and welding-type configurations. However, there is a shift toward a bond-adhesive lamination method using self-bond material to create high-efficiency motors. The self-bond method is a layering method using bond-coated steel plates. In this study, we investigated the factors affecting the induction and convection heat fusion temperatures, temperature distribution characteristics, and stacking factor of heat-fused products using self-bond material. Additionally, experiments were conducted to analyze the heat transfer properties during the fusion process and the temperature distribution changes over time. In the heat fusion experiments, induction resulted in temperature increases of 277.1 °C (Zone ①), 161.4 °C (Zone ②), and 103.2 °C (Zone ③) after 120 s of heating. Carbonization occurred due to higher temperature rise in Zone ① compared to Zones ② and ③. On the other hand, convection required 330 min to reach a product fusion temperature of 209 °C, but the temperature deviation was more uniform compared to induction. Furthermore, we analyzed the plate thickness, glue coating thickness, and weight of self-bond material Lots A and B. The experimental results for the stacking factor before and after fusion showed that Lot B had a stacking factor of 96.98%, which was 0.48% higher than Lot A. The fusion process significantly influenced the stacking factor.”

The liquid piston thermoacoustic stirling engine (LPTSE) is a type of Stirling engine that utilizes the reciprocating motion of liquid columns within U-tubes instead of a traditional mechanical piston, enabling the working gas to experience the Stirling-like thermodynamic cycles. To date, LPTSE has primarily been used for cooling purposes; however, it also holds the potential for electricity generation. This paper presents a numerical investigation of methods for generating electric power from LPTSE. The first method involves the use of a linear alternator to harness the oscillation of the gas column, while the second method employs a float-type alternator to utilize the oscillation of the liquid column. Numerical simulations were performed utilizing DeltaEC, a dedicated design tool founded on the principles of linear thermoacoustics theory. The results showed that proposed methods did not alter the acoustic fields in the regenerator, indicating that the engine operates with the Stirling-like thermodynamic cycle and achieves high thermal efficiency. The linear alternator generated an electric power of 0.2 W with a thermal-to-electric efficiency of 2.48(%) under a load resistance of 1 (Omega), whereas the float-type alternator produced an electric power of 0.7 W with thermal-to-electric efficiency of 4.5(%) under a load resistance of 7 (Omega). The research results presented in this paper offered perspectives on electricity generation from the LPTSE.

This research explores the cutting performance of newly developed DURANA (AlTiN/TiSiXN)-coated carbide tool and investigates the lubrication–cooling performance of ionic liquid-based lubricants for improving the machinability of biomedical-grade stainless steel under sustainable minimum quantity lubrication. This article also explores comparative performance assessment between two different ionic liquid-based lubricants (1-methyl 3-butylimidazolium tetra fluoroborate, BMIM BF4) and (1-methyl 3-butylimidazolium hexafluorophosphate, BMIM PF6). Technological performance characteristics such as cutting force and thrust force, flank and crater wear, surface integrity (surface roughness, surface morphology, residual stress, microhardness), chip morphology, and cutting temperature are taken into account when evaluating the machinability of biomedical-grade stainless steel. In addition, the study analyses the thermo-physical and tribological properties of ionic liquid (IL)-based lubricants for machining. The lubricant based on BMIM PF6 IL exhibited an improved wear resistance of coated tool, higher viscosity as well as thermal conductivity with minimal contact angle in comparison with the lubricant based on BMIM BF4. Due to the development of improved chip morphology, lower cutting forces and minimum cutting temperature, enhanced machined surface integrity, and decreased tool wear, the turning with BMIM PF6 IL-based lubricant committed superior than BMIM BF4-based lubricant.

Centrifugal pumps play a crucial role in industrial operations involving fluid transport. The quest for optimizing efficiency and reducing energy usage is a driving force behind research into their performance. The literature continues to offer opportunities for the creation of models that accurately depict the head generated by pumps, with a particular focus on impellers. The current pumps, however, are still far from being completely optimized. The idea of this paper is to conduct an analysis of energy losses and propose a mathematical expression to represent the head produced by a radial impeller, P23 model, working with water flow, considering that head is influenced by losses due to recirculation, shock/incidence, internal friction. The head losses are quantitatively evaluated from experimental data acquired via particle image velocimetry, which provides information on velocity vector direction and wall shear stress, both useful for the analysis. Our results reveal that the loss due to friction is the most significant, accounting for 40–90% of the total head loss, while shock and recirculation losses are restricted to 35% and 25%, respectively. Friction factors vary from 1.0 to 26 depending on the flow rate, as a result of wall shear stresses reaching up to 430 N/m², mainly influenced by pressure and pseudoforces. The head calculated through the new proposed expression is finally compared with the actual head generated by the impeller, measured via experiments dedicated to assess the pump performance. According to our results, the relative deviations between the calculated and measured heads are limited to 5%. Although our results have been validated for a single P23 impeller geometry, the methodology developed here can be extended to other impellers in the future. The results may thus represent a step forward for designing more efficient and power-saving pumps.

Adhesive bonding has been replacing traditional joining methods such as welding, bolting, and riveting in the design of mechanical structures in the automotive, aerospace and aeronautic industries. This joining method has several advantages over traditional methods such as ease of manufacture, lower costs, ease of joining different materials, higher fatigue resistance, and high corrosion resistance. Although tubular adhesive joints have varying applications, such as in truss structures and vehicles, machine axles, and piping, different joint configurations exist, such as rod-tube joints (RTJ), which are not conveniently addressed in the literature. This work compares the tensile performance of adhesively bonded RTJ between aluminium alloy components (AW6082-T651), considering the variation of the main geometric parameters: overlap length (L_O), tube thickness (t_S), rod diameter (d), adhesive fillet angle (f), and type of adhesive. The Taguchi’s method was employed in the elaboration of the applied design of experiments (DoE). To compare the RTJ behaviour, a numerical analysis was carried out through finite element analysis (FEA) and cohesive zone modelling (CZM). Peel (σ_y) and shear (τ_xy) stresses in the adhesive layer were initially obtained by applying purely elastic models. CZM modelling made possible to obtain the damage evolution in the adhesive layer, the maximum load (P_m) and dissipated energy (U) at P_m of the adhesive joints. As a result of applying the Taguchi method, the adhesive joint that showed the best overall performance used the adhesive Araldite^® AV138, L_O = 40 mm, d = 20, and t_S = 3 mm.

Sandwich structures and auxetic materials have had a significant impact on various applications as energy absorbers. The purpose of this study is to manipulate the deformation mechanism of sandwich beams by using a combination of rigid and flexible material components in the core structure, thus improving their absorption capacity and flexural behavior. The effects of flexible and rigid material layer arrangements and the percentage of flexible/rigid material in the core structures were investigated by using experimental and numerical methods. Three-point bending tests of fourteen different multi-material auxetic cores and two different single material core structures were carried out using flexible TPU and rigid PLA 3D printed layers. Then, the FE analysis was performed parametrically to reveal the effects of t/l ratios of the unit cell on the flexural behavior and energy absorption performance of the sandwich beams. Experimental studies shows that the TPPP, PTPT, and TTPT hybrid core arrangements exhibit greater energy absorption capacities (9.07 J, 9.61, and 9.60 J, respectively). The deformation mechanism of the flexible and rigid materials and inclined struts of the core structures play a key role in the flexural strength and energy absorption capacities. For example, the plastic deformation mechanism could be spread over a wider area to delay the localized fractures by reinforcing the rigid auxetic core with flexible material. Also, the strength and energy absorption could be increased when the bottom layer is made of rigid material. It is recommended to avoid using adjacent layers of the flexible material because they have lower flexural strength. The parametric analysis show that the energy absorption performance could be increased within the range of ~ 5 to ~ 20% when the t/l ratio decreases.