Optimal Thickness Ratio Research Articles

An Optimization Approach for Enhancing Energy Efficiency, Reducing CO2 Emission, and Improving Lubrication Reliability in Roller Bearings using ABC Algorithm

Friction and energy waste pose significant challenges in various industrial processes. Lubrication plays a crucial role in reducing friction and optimizing energy consumption. This study focuses on analyzing, simulating and calculation the oil film thickness, friction levels, energy losses, and CO2 emissions. The objective is to optimize lubrication conditions to enhance performance, improve energy consumption, and maximize lubrication efficiency for rolling bearings in a centrifugal fan. The simulation utilizes ANSYS CFX software, MATLAB programming. The optimal oil viscosity grade is determined based on two objectives by using artificial bee colony algorithm (ABC): minimizing energy consumption (thus reducing CO2 emission) and achieving the optimal oil film thickness and viscosity ratio. The findings reveal that, under the current lubrication conditions and normal fan operation, energy losses due to oil friction amount to 36.3 MWh per year, with CO2 emissions resulting from power losses reaching 18,750 kilograms per year. By transitioning to the optimized oil grade, energy savings of 1.08 MWh per year and a corresponding reduction of 557 kilograms in CO2 emissions per year can be achieved.

Dynamic response and safety performance of composite-laminated heliostat under hail impact

ABSTRACT Areas rich in solar energy are prone to strong convective weather, leading to severe hail disasters, which makes heliostats under the threaten of hail impacts. An evaluation model of composite laminated heliostat under hail impacting is established and validated. Subsequently, the effect of interlayer type and thickness ratio on the dynamic response and safety assessment of composite laminated heliostats impacted by hail are investigated. Additionally, the velocity thresholds for hail terminal velocity of composite laminated heliostats with a thickness range of 2–4 mm, based on the optimal thickness ratio, are studied. The results indicate that the maximum principal stress value of the composite laminated heliostat remains similar to that of the single-layer heliostat when the interlayer types are SentryGlas Plus (SGP) and Polyvinyl Butyral (PVB). The maximum principal stresses of single-layer heliostats with thicknesses of 2-4 mm are 2.92, 1.50, and 1.35 times, compared to the first-layer glass of composite laminated heliostat with the same thickness under the optimal thickness ratio, which indicates that the hail resistance of the composite laminated heliostat is superior to that of the single-layer heliostat. The findings offer the guidance for the hail resistance of composite laminated heliostat under hail impact.

Torque‐tuned I‐V characteristics in a piezoelectric semiconductor composite fiber

AbstractThis paper studies the multi‐physical fields in a torsional composite fiber composed of a non‐piezoelectric semiconductor (PS) core coated with a piezoelectric dielectric shell. Based on the three‐dimensional framework of piezoelectricity and drift‐diffusion theory, we develop a nonlinear one‐dimensional model that incorporates the warping deformation, shear deformation, and axial variations of the electric field and charge transportations. A One‐dimensional model is linearized for small perturbations of charges, and we obtain the analytical solutions for single rods or PN junctions when torques are applied, which explicitly illustrates the electromechanical fields and redistribution of mobile charges. We also examine how the thickness of the composite rods affects the interaction between the piezoelectric and semiconductor components in the model. The optimal thickness ratio for maximizing the overall mobility of carriers has been discovered. This enables us to modify the thickness ratio to achieve the greatest PS interaction performance. Based on the nonlinear equations, we analyze the relationships between electric currents and applied voltages on the end of rods. Finally, we examine how twisting moments influence the characteristics of this I‐V relationship. The presented study provides a potential application for mechanical switches or sensors for PSs.

Direct-Contact Seebeck-Driven Transverse Magneto-Thermoelectric Generation in Magnetic/Thermoelectric Bilayers.

Transverse thermoelectric generation converts temperature gradient in one direction into an electric field perpendicular to that direction and is expected to be a promising alternative in creating simple-structured thermoelectric modules that can avoid the challenging problems facing traditional Seebeck-effect-based modules. Recently, large transverse thermopower has been observed in closed circuits consisting of magnetic and thermoelectric materials, called the Seebeck-driven transverse magneto-thermoelectric generation (STTG). However, the closed-circuit structure complicates its broad applications. Here, STTG is realized in the simplest way to combine magnetic and thermoelectric materials, namely, by stacking a magnetic layer and a thermoelectric layer together to form a bilayer. The transverse thermopower is predicted to vary with changing layer thicknesses and peaks at a much larger value under an optimal thickness ratio. This behavior is verified in the experiment, through a series of samples prepared by depositing Fe-Ga alloy thin films of various thicknesses onto n-type Si substrates. The measured transverse thermopower reaches 15.2 ± 0.4µVK-1, which is a fivefold increase from that of Fe-Ga alloy and much larger than the current room temperature record observed in Weyl semimetal Co2MnGa. The findings highlight the potential of combining magnetic and thermoelectric materials for transverse thermoelectric applications.

Effects of piezoelectric synthetic jet actuator parameters on synthetic jet formation process and actuator performance

Aiming at the problem that the non-linearity between the piezoelectric vibrator deflection and the excitation amplitude of the piezoelectric synthetic jet actuator (SJA) causes it difficult to obtain the variation laws of the synthetic jet (SJ) velocity accurately, a theoretical model of the whole flow field of the piezoelectric SJA is established and four important parameters (half period jet mean velocity, Reynolds number, effective jet length and energy) for evaluating the performance of the SJ are proposed. Then a two-dimensional axisymmetric numerical simulation is carried out with k-ω turbulence model to study the SJ formation process and the velocity characteristics of the SJ at the orifice. The results show that the fluid pressure in the cavity is the main reason causing the non-linearity between the piezoelectric vibrator deflection and the excitation amplitude, the influence of which decreases with the increase of the orifice diameter. The SJ velocity increases first and then decreases slowly with the increase of excitation frequency. The extreme point occurs at the first resonant frequency of the piezoelectric vibrator and the position of the maximum velocity occurs at 0.5 mm outside the orifice. Other conditions being constant, both the piezoelectric vibrator deflection and jet velocity have a maximum value when the radius ratio of the piezoelectric layer to the elastic layer is 0.75. Smaller piezoelectric layer thickness leads to larger lateral displacement of the piezoelectric vibrator, and the optimum thickness ratio is 0.25. The results of this study have important guiding significance for accurately obtaining the variation laws of the SJ velocity as well as rationally designing the piezoelectric SJA.

Discharging performance evaluation and optimization of a latent heat thermal energy storage unit with helm-shaped fin

Latent heat thermal energy storage with phase change materials can help mitigate the imbalance between the energy supply and demand. Improving the discharging efficiency is crucial to the performance of thermal energy storage units. This paper explores the enhancement performance of helm-shaped fin on phase change materials solidification in a vertical shell-tube storage unit. Numerical model was built to examine the solidification performance of the thermal energy storage unit and its effectiveness was validated by experimental data from literature. The effect of the dimensionless offset (O, defined as the ratio of the minimum distance between the rectangular part of helm-shaped fin and the tube to the distance between the shell and the tube) on the thermal performance was firstly investigated. Results showed that an O of 0.458 is optimum, which shortens the solidification time by 23.9% compared to the O of 0. With this offset, the effects of volume, thickness and height ratios of the annular part to the rectangular part of the helm-shaped fin were further investigated. Results showed that the phase change materials solidification rate increases as the thickness ratio increases and height ratio decreases. The optimum thickness and height ratios are 8 and 0.473 respectively, which reduces the solidification and melting times by 54.5% and 22.1% respectively compared to the traditional annular fin at the same fin volume.

The effect of three-layer liner on the jet formation and penetration capability of shaped charge jet

In order to solve the problem of insufficient penetration ability of common liner, a new three-layer liner was proposed. AUTODYN software was used to simulate the efflux forming process of three-layer liner. The influence of four different impact impedance liner materials and different thickness ratio of three-layer liner on efflux performance was studied. In order to study the penetration ability of shaped charge to semi-infinite target plate, the penetration calculation of the target plate was carried out by taking several standoff under different thickness ratios. The optimal thickness ratio of three-layer liner was determined by studying the penetration depth and opening size of the target plate. The results show: By comparing the matching of liner materials with different impact impedances, the head velocity, effective length, total energy, total kinetic energy and effective jet mass of the jet formed when the three-layer liner material is AL 2024, copper and nickel from the outside to the inside are the best. In the analysis of the matching of the thickness ratio of the three-layer liner, the key to the jet forming is the thickness ratio of the outer liner. Within a certain range, the greater the proportion of the thickness of the outer liner, the better the jet forming; when the material of the three-layer liner is AL 2024-copper-nickel from outside to inside, the thickness ratio of the liner is 4/1/1 from outside to inside, and the jet forming is the best. The maximum penetration depth of the shaped charge with a thickness ratio of 1/1/4 from the outside to the inside of the three-layer liner is 395.5 mm, which is 52.3% higher than that of the shaped charge with a double-layer liner. Compared with the shaped charge with single-layer liner, the penetration depth is increased by 62.6%. When the thickness ratio of the three-layer liner is 1/1/4 from the outside to the inside, the maximum entrance diameter of the target plate is 14.3 mm, which is the same as that of the shaped charge with the double-layer liner. Compared with the shaped charge with single-layer liner, the entrance diameter is in-creased by 14.4%.

Random vibration of sandwich beam with a shear thickening fluid core

The dynamic performances of a sandwich beam with a shear thickening fluid (STF) core subjected to a random excitation are investigated. First, the STF is prepared and a new constitutive model is proposed based on the oscillatory rheological measurements. Next, a flexural vibration model of the sandwich beam with an STF core under random load is developed, and a parametric study is carried out. It is found that the response frequencies and damping ratios for the first three modes of the beam increase with the standard deviation of the external random excitation. The sandwich beam with STF provides better damping for larger broadband excitation. Additionally, the beam with an STF core will produce a response both inside and outside the load frequency domain. Furthermore, an optimal thickness ratio for the structure that maximizes the damping ratio of the structure is identified. It is important to note that this optimal thickness ratio of the structure varies with the order of vibration modes. This research provides valuable insights into the design of structures using STF and also contributes to the development of dynamic constitutive models for STF.

Study on seismic behavior of double leg C-type cold-formed thin-walled steel frame

The cold-formed steel (CFS) frame has the advantages of high strength, light weight, high construction efficiency, so it has been widely applied in building structures. However, the research on the seismic performance of multistory frames, especially those with braces, is rarely reported, the design method is also incomplete. In view of this, a pseudo static experiment of a three story double leg C-section CFS frame with brace is carried out. The bearing capacity, ductility, stiffness degradation and energy dissipation performance of the specimens are studied. The finite element analysis (FEA) method is used to simulate the failure process of the CFS frame and the design suggestions are proposed. The experiment result show that the failure process of the cold-formed thin-walled frame without braces has satisfactory ductility and energy dissipation performance; For framed CFS frame, the lateral stiffness and bearing capacity of the CFS frame increases, but the ductility decreases. Replacing double angle steel brace by steel plate strip brace can improving the seismic performance of structures, but there is an optimal width thickness ratio of steel plate strip. In this paper, the optimal width thickness ratio of brace is 5.0. When the design suggestions proposed in this paper are met, the CFS frame can achieve “strong structure, weak brace”, so as to improve the seismic performance of the frame.

Model-Based Analysis and Optimization of Acidic Tin–Iron Flow Batteries

Acidic tin–iron flow batteries (TIFBs) employing Sn/Sn2+ and Fe2+/Fe3+ as active materials are regarded as promising energy storage devices due to their superior low capital cost, long lifecycle, and high system reliability. In this paper, the performance of TIFBs is thoroughly investigated via a proposed dynamic model. Moreover, their design and operational parameters are comprehensively analyzed. The simulation results show that (i) a flow factor of two is favorable for practical TIFBs; (ii) about 20% of the system’s efficiency is decreased as the current density increases from 40 mA cm−2 to 200 mA cm−2; (iii) the optimal electrode thickness and electrode aspect ratio are 6 mm and 1:1, respectively; and (iv) reducing the compression ratio and increasing porosity are effective ways of lowering pump loss. Such in-depth analysis can not only provide a cost-effective method for optimizing and predicting the behaviors and performance of TIFBs but can also be of great benefit to the design, management, and manufacture of tin–iron flow batteries.

Modelling a near perfect temperature tunable multiband VO2 based photonic-plasmonic absorber within visible and near infrared spectra

This work demonstrates thermal and optical stability with multiple near perfect absorption in a polarizing sensitive one-dimensional vanadium dioxide (VO2) graphene-based nanocomposite plasmonic structure within visible to infrared region (IR). Proposed structure in each phase of VO2 has multiple perfect optical absorption peaks within visible range with a Q-factor near ∼45 which leads the structure to work like an optical switch. An increase in absorption is achieved through plasmonic polaritons of a nearby Ag thin layer directly or through photonic crystal. The temperature turnability of VO2 leads the proposed structure a tunable optical absorber with a hysteresis loop from low to nearly perfect absorbance spectrum. The octonacci quasi periodic proposed structure has highest multiple perfect absorber spectrum comparing other photonic sequences. The peaks of absorption have blue shifted with an increase in volume fraction in both phases. The optical absorption of the structure in metal phase mode alters from wide band to multiple narrow bands with the increment of permittivity of the host composite material within the 1000–1600 nm range. The absorption maximizes in TE mode comparing TM mode due to polarization sensitivity. The structure with optimal thickness and volume mixing ratio in composite has temperature dependency with a thin layer of VO2 has ∼90% absorption. The absorption of the structure can be tuned in both heat and cool mode function of the phase change material (PCM) at an optimum frequency within visible to IR spectrum. These thermal bistable activities may enhance the optical features of the devices.

Experimental study on sorption–desorption characteristics of natural composite desiccant with metal embedment

The present study investigates the effect on total moisture sorption, moisture sorption rate, moisture desorption rate, and reduction in the temperature of dehumidified air of metal-embedded natural composite desiccants (MENCDs), which can be used in dehumidification systems. A natural composite desiccant, in which the unutilized portion of the spherical desiccant material is replaced with a metallic ball, is proposed. Stainless steel balls with a diameter of 4.75 and 6.35 mm are used to make different thickness ratios (TR = 1, 0.525, and 0.365) of MENCDs. The natural composite desiccant is prepared from dried cow dung and polyvinyl pyrrolidone with a ratio of 3:1. Experiments are conducted to find the optimum thickness ratio of MENCDs. The total moisture sorption, moisture sorption rate, total heat load reduction, and exergy efficiency of these dehumidification systems are investigated under different relative humidities (RH = 65% to 85%), and at a constant temperature and velocity. Desorption characteristics are tested under 328 K and 5% RH. The total moisture sorption of MENCDs with a TR of 0.365 is found to be 11.84 g/100 g, which is 17% higher compared to natural composite desiccants (i.e., TR = 1) at 85% RH, whereas, the total moisture sorption rate is 0.4 g/100 g⋅min, which is 20.57% higher for TR of 0.365 compared to TR = 1. Moisture desorption rate for TR = 0.365 is 16.66% higher compared to TR = 1. The average exergy efficiency of these systems is 60%. The average exergy efficiency of these composite desiccants with a TR = 0.365 is 9.6% higher compared to TR = 1. The average total heat load reduction for composite desiccants with a TR = 0.365 is 24% higher compared to TR = 1. The experimental study shows that the MENCDs will help to increase total heat load reduction, sorption and desorption rate, and total moisture sorption of dehumidified air with optimum thickness ratio for enhanced utilization of a composite desiccant for dehumidification systems.

Geometry-Dependent Magnetoelectric and Exchange Bias Effects of the Nano L-T Mode Bar Structure Magnetoelectric Sensor.

The geometry-dependent magnetoelectric (ME) and exchange bias (EB) effects of the nano ME sensor were investigated. The sensor consisted of the Longitudinal-Transverse (L-T) mode bi-layer bar structure comprising the ferromagnetic (FM) and ferroelectric (FE) materials and the anti-ferromagnetic (AFM) material. The bi-layer ME coefficient was derived from constitutive equations and Newton's second law. The trade-off between peak ME coefficient and optimal thickness ratio was realized. At the frequency × structure length = 0.1 and 1200, minimum and maximum peak ME coefficients of the Terfenol-D/PZT bi-layer were around 1756 and 5617 mV/Oe·cm, respectively, with 0.43 and 0.19 optimal thickness ratios, respectively. Unfortunately, the bi-layer could not distinguish the opposite magnetic field directions due to their similar output voltages. PtMn and Cr2O3, the AFM, were introduced to produce the EB effect. The simulation results showed the exchange field starting at a minimum PtMn thickness of 6 nm. Nevertheless, Cr2O3 did not induce the exchange field due to its low anisotropy constant. The tri-layer ME sensor consisting of PZT (4.22 nm)/Terfenol-D (18 nm)/PtMn (6 nm) was demonstrated in sensing 2 Tbit/in2 magnetic bits. The average exchange field of 5100 Oe produced the output voltage difference of 12.96 mV, sufficient for most nanoscale magnetic sensing applications.

Simulation Study of FEUDT Structure Optimization and Sensitive Film Loading of SAW Devices.

In order to further improve the degree of frequency response of the surface acoustic wave (SAW) sensor for gas detection, the structure of the forked-finger transducer was analyzed, and its optimal structural parameters were simulated and designed. The simulation model of the unidirectional fork-finger transducer is established by using COMSOL finite element software. The thickness of the piezoelectric substrate, the electrode structure and material, and the thickness of the coating film are optimized and simulated. The results show that: the optimal thickness of the piezoelectric substrate is 3λ. The optimal thickness ratio and the lay-up ratio of the forked-finger electrode are 0.02 and 0.5, respectively. The Al electrode is more suitable as the a forked-finger electrode material compared to Cu, Au and Pt materials. Under the same conditions, the metal oxide-sensitive film (ZnO and TiO2) has a higher frequency response than the polymer-sensitive film (polyisobutylene and polystyrene), and the best sensitive film thickness range is 0.5~1 μm.

Magnetically induced electromechanical fields in a flexoelectric composite microplate

We studied electromechanical fields in a composite plate with flexoelectric and piezomagnetic layers. The governing equations and complete boundary conditions are proposed in terms of the couple stress theory to characterize the size-dependent effects and flexoelectric effects. The constitutive relations of centrosymmetric cubic and hexagonal crystals are both provided. To demonstrate the newly developed model, the static bending and forced vibration problems of a simply supported rectangular plate are studied with the aid of Navier’s technique. Numerical results showed that various deformed shapes and electric potential distributions in the current microplate can be effectively manipulated by varying the magnitude of magnetic fields or flexoelectric coefficients. The relevant electromechanical properties can also be adjusted by altering the thickness ratio of the piezomagnetic and flexoelectric layers, which leads to a maximum value of the displacement or electric potential for an optimal thickness ratio. This paper provides an innovative idea for non-contact flexoelectric applications when magnetic fields are involved.

Optimal magnetoelectric coupling performance of Terfenol-D/PZT composites in resonance state under bias magnetic field

Laminated magnetoelectric (ME) composites with various thickness ratios were optimized, fabricated and experimentally investigated in this work. The Terfenal-D/PZT specimens with optimal thickness ratio between the magnetostrictive phase and piezoelectric phase, and two other values were tested for their ME coupling performance. The coupling voltage output increases linearly with the increase of DC bias magnetic field. The ME voltage coefficient increases more than 100 times in the resonance state for the optimal laminate. The DC bias magnetic field affects the ME voltage coefficient significantly, and also has little effect on the resonant frequency. The strength of AC magnetic field also slightly affects the ME voltage coefficient in resonance state, but does not affect the resonant state under which the same DC magnetic field is required. The experimental results can help understand the coupling performance of ME composite under bias magnetic field and prompt the application of ME devices.

A quasi-dynamic model and thermal analysis for vapor chambers with multiple heat sources based on thermal resistance network model

The heat and mass transfer mechanism in a vapor chamber is a complex process. The thermal resistance network model is an effective tool to describe the heat transfer behavior of a vapor chamber (VC). An improved quasi-dynamic multi heat source model has been developed in this study to analyze the temperature distribution of a vapor chamber with multiple heat sources under dynamic operating conditions. The accuracy of the proposed model has been validated by experiments. The influence of the VC thickness and thickness ratio has also been analyzed. Different heat source inputs have been used to study the startup characteristics of the vapor chamber. The results from simulations reveal that the optimum thickness ratio for a VC depends on the thermal resistance as well as heat transfer limit. Under the same cooling conditions, a longer startup time for a VC was observed with the increase in heating power. In addition to this, the thermal resistance of a vapor chamber was found to increase slightly at a higher temperature. The model in this study has certain guiding significance for the analysis of heat transfer and the design of a VC under various working conditions. • Thermal resistance network model for vapor chambers with multiple heat sources is established. • Quasi-dynamic approach for transient analysis with high accuracy. • The influences of thickness and optimum thickness ratio are analyzed. • Startup characteristics and thermal resistance are analyzed.

Fracture analysis of a non-homogeneous coating structure with dual interfaces under thermal shock

To solve the thermal fracture problem of non-homogeneous coating structure (NCS) with dual interfaces under strong transient thermal loading, this paper proposes a method to extract fracture parameters by combining the Newmark method and the transient interaction energy integral method (IEIM). The strong transient temperature and the transient thermal stress intensity factors (TSIFs) of NCS with dual interfaces under strong transient thermal load can be obtained through the proposed method. The interfaces are divided into an ideal interface, weak interface, and strong interface according to the continuity of the material parameters of NCS at the interface. Firstly, the influences of Young's modulus, thermal relaxation time, thermal expansion coefficient, and density continuity on TSIFs at strong and weak interfaces are studied. Then, the crack growth laws under thermal shock at the strong and weak interfaces are analyzed. Finally, according to the influence of the coating thickness on TSIFs, the optimal thickness ratio of the dual interface structure ranging is selected to minimize the likelihood of thermal fracture. This work can be used for the thermal design, evaluation, and engineering applications of NCS.

The effects of an LPCVD SiN x stack on the threshold voltage and its stability in AlGaN/GaN MIS-HEMTs

In this work, we systematically studied the stoichiometry and thickness effects of low-pressure chemical vapor deposited SiN x bilayer stacks on the electrical properties of AlGaN/GaN heterojunction-based metal–insulator-semiconductor high electron mobility transistors. A Si-rich SiN x single layer reduces threshold voltage shift and hysteresis under gate stress but gives rise to high gate leakage. A near-stoichiometric SiN x single layer suppresses gate leakage but causes poor gate stability. A bilayer SiN x stack with an optimized thickness ratio improves both the gate stability and on-resistance while maintaining a low current leakage. The bilayer SiN x stack consisting of a 5 nm Si-rich SiN x interfacial layer and a 15 nm SiN x capping layer resulted in the lowest sheet resistance and the highest gate stability. Such enhanced gate stability is explained by the low density of trap states and the weakened electric field at the Si-rich SiN x /GaN interface and an extra positive charge at the bilayer interface.

Thermal analysis in the evaporation of flowing thin liquid film confined by gradient or double-layered porous layer subjected to air jet impingement

The porous metal foam subjected to air jet impinging is set above thin liquid fluid passing through the heating surface to maintain its thickness, in which the heat from heating surface is released in the convection with the thin liquid film to the surroundings, as well as across the thin liquid film and metal foam to the outside surface where the evaporation and convection occur. Local thermal non-equilibrium (LTNE) occurs, so the double energy equations together with Brinkman-Darcy model are employed to describe the heat transfer in metal foam, as well as N–S equations account for the flow of thin liquid film. The effects of the different porosity and particle diameter distributions (e.g. constant, linearly increasing/decreasing and stepwise increasing/decreasing), as well as thickness ratio between the bottom and upper layers with different porosities and particle diameters in stepwise variation on the cooling performances are numerically analyzed. The simulations are validated with the published experiment data. The lower heating surface and larger heat transfer coefficient (HTC) occur in the presented mode with the relatively lower porosity and particle diameter. The 67.47% rise ratio of the peak HTC in the mode with porosity of 0.3 happens than that with porosity of 0.9. The optimized thickness ratio together with the porosity and particle diameter in the bottom and upper layers influence the heat to be transported in the convection with liquid fluid to the downstream side or across the metal foam to its outside surface. All results can be considered into the promotion and application of coupling the air jet impingement and porous metal foam above thin liquid film to enhance heat transfer.